Several of the agents of concern specified by the U.S. Congress in the Gulf War legislation (P.L. 105-368 and P.L. 105-277)1 were not only used in the 1990–1991 Gulf War but are also applicable to exposures in the Post-9/11 conflicts in Iraq and Afghanistan. Many of them are not commonly encountered by service members stationed at military installations in the United States or by the U.S. general public. Those agents include the chemical warfare agents sarin, tabun, and mustard gas; infectious diseases endemic to Southwest Asia; several vaccinations (including those against anthrax and botulinum); depleted uranium (DU); pyridostigmine bromide (PB); and hexavalent chromium (Cr6). Exposures to these agents distinguish military personnel deployed to the Persian Gulf region from those who did not deploy to the Middle East. The health outcomes associated with exposure to these agents were reviewed by previous Gulf War and Health committees (IOM, 2000, 2005, 2008a). Deployment to a war zone itself has been associated with several adverse health reactions, as described in Gulf War and Health, Volume 6 (IOM, 2008b). The potential impact of each of these exposures on the reproductive and developmental health of veterans and their descendants is considered in this chapter, beginning with the pervasive effect of deployment itself. The following sections review previous National Academies’ reports, authoritative reviews, and new literature identified by the Volume 11 committee on deployment exposures and associated reproductive and developmental effects.
The committee uses the term “deployment” to refer to a military assignment or assignments leading to the collective and complex set of chemical, biological, radiological, and physiological exposures and psychological impacts that may be encountered in theater. Numerous studies have investigated the
1 P.L. 105-368 Veterans Program Enhancement Act of 1998. Sec 1-101 Agreement with the National Academy of Sciences regarding the health consequences of veterans serving in the Persian Gulf. P.L. 105-277 was the emergency appropriations given to the National Academy of Sciences to study “exposure to toxic agents or wartime hazards.” This was codified in Compensation for Disabilities Occurring in Persian Gulf War Veterans, 38 USC 1117.
potential health effects of deployment since 1993. These studies usually compare military personnel who deployed to the Persian Gulf theater of operations with those who deployed to other regions (for example, Bosnia or Somalia) or who remained in garrison in the United States. Four volumes of the Gulf War and Health series have reviewed the literature that compares the health status of these veteran populations as well as the available information on the many potential and variable exposures that may have occurred in theater (IOM, 2006b, 2008b, 2010; NASEM, 2016). Those reports found that there was inadequate/insufficient evidence for any reproductive or developmental effects (including birth defects, adverse pregnancy outcomes, fertility problems, or genitourinary conditions). One exception was found: several studies of different groups of veterans found that sexual difficulties were reported more frequently by male veterans who had deployed than by veterans who had not deployed. This finding led the Volume 10 committee to conclude that there was limited/suggestive evidence of an increased prevalence of self-reported sexual difficulties among Gulf War veterans (NASEM, 2016). Although the other reproductive and developmental effects had been reported in the literature, the evidence was limited by methodologic issues, inconsistent results, and sparse data.
The Volume 11 committee identified several new studies that examined reproductive and developmental health outcomes in veterans, but the results are inconclusive because of low response rates. Recent surveys by the Department of Veterans Affairs (VA) have collected information on the reproductive health of Gulf War and Post-9/11 era veterans. Although a 2012 survey of Gulf War veterans (with a 50% response rate) inquired about reproductive health for female veterans only, survey results published as of 2016 did not include the status of female or male veterans’ reproductive health (Dursa et al., 2016). A 2009–2011 survey of 30,000 Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF) deployed and 30,000 nondeployed veterans who served between 2001 and 2008 asked respondents about infertility. There were 20,370 respondents, for a 34.3% response rate. Results indicated that infertility is a concern among both male (n=16,056) and female (n=4,314) veterans. Compared with men, female veterans had similar odds of a lifetime history of infertility (OR=1.07, 95% CI 0.94–1.20), but the actual risk of infertility associated with deployment was not determined (Katon et al., 2014a).
There is a dearth of studies on the reproductive effects of deployment and deployment exposure on male and female veterans. Buller et al. (2007) reviewed gynecology visits at Camp Doha, Kuwait, from August 2003 through April 2004. Of the 1,737 visits, 77 had a positive pregnancy test, 77% of the pregnancies occurred in country, and 23% of the women had been pregnant when they arrived in country.
Reproductive Effects in Men and Women
One study using administrative data from VA examined gestational diabetes and hypertensive disorders of pregnancy among women who used maternity benefits. Compared with the general population of civilian women, Post-9/11 deployed women using VA maternity benefits (n=2,288) had a higher risk of gestational diabetes (standardized incidence ratio [SIR]=1.40, 95% CI 1.16–1.68) and hypertensive disorders (SIR=1.32, 95% CI 1.15–1.51) after controlling for maternal age and year of delivery. No comparisons were made between deployed and nondeployed women veterans (Katon et al., 2014b). The Volume 11 committee notes that although gestational diabetes and hypertensive disorders are endpoints that are possibly mediated through abnormalities in placental implantation, this effect was not considered in this study.
The Millennium Cohort Study is a longitudinal study initiated in 2001 by the Department of Defense (DoD) to assess the long-term health of service members from all military branches over an extended
period. This study assessed miscarriages in 3,366 female veterans who deployed to Iraq and Afghanistan. Self-reported miscarriage, self-perceived impaired fecundity, combat exposures, and other lifestyle and health metrics and self-perceived reduced fertility was assessed by a questionnaire and documented for 11,183 female veterans (Ippolito et al., 2017). Women completed questionnaires in 2004–2006 and again in 2007–2008, and their deployment status, including combat exposure, was determined from personnel files. Neither deployment status, with or without combat exposure, nor days deployed nor life stressors were associated with a significantly increased risk of having a miscarriage (ORs ranged from 0.86 to 1.67; none were significant) or of having had self-perceived reduced fertility in the previous 3 years (ORs ranged from 0.86 to 1.24; none were significant).
No new studies on the effects of deployment on male reproduction were identified by the Volume 11 committee.
Adverse Pregnancy Outcomes
The Volume 11 committee identified a systematic review of the impacts of active-duty military service on the reproductive health of female service members and male and female veterans from around the world, although most of the 46 studies cited in the review were of U.S. women (Lawrence-Wood et al., 2016). There was insufficient evidence that military service had an effect on pregnancy outcomes, including preterm births and birth defects, although there was evidence that deployment was associated with ectopic pregnancies. The authors noted that the small number of studies limited any definitive conclusions. Military occupational exposures, whether during deployment or not, were associated with birth defects but not with fertility issues, ectopic pregnancy, or miscarriage, and the evidence was mixed for preterm births.
The association between adverse birth outcomes among U.S. Navy women and occupational and environmental exposures experienced by either the mother or the father was explored by Hourani and Hilton (2000). A mailed survey of active-duty women serving in the U.S. Navy who gave birth to a live infant between January and October 1993 in any of three large naval hospitals yielded a response rate of 56%. Women were asked about their own and their partners’ exposures in the 3 months prior to conception and about adverse birth outcomes (low birth weight, preterm birth [<37 weeks], birth defects, fetal distress prior to or during delivery, and small for gestational age). Compared with civilian beneficiaries, active-duty women who self-reported exposure to petroleum products in the home were at an increased risk of having a low-birth-weight infant (<2,500 g; OR=2.4, 95% CI 1.3–6.56). Paternal exposure to pesticides at work and maternal exposure to heavy metals at work were both associated with an increased risk of having a preterm birth (<37 weeks; OR=2.6, 95% CI 1.28–5.43 and OR=2.2, 95% CI 1.11–4.47, respectively). Fetal distress and small for gestational age were not associated with any maternal or paternal exposures. Thus, more research should be conducted to see if there is an association between the exposures of interest and reproductive and developmental effects.
A study by Conlin et al. (2012) examined birth outcomes in children born to men and women veterans who had deployed within a 3-mile radius of a documented burn pit in Iraq. The authors used the DoD Birth and Infant Health Registry to identify live infants born to deployed men or women between 2004 and 2007. Infants born to deployed women with burn pit exposure were not at increased risk of being preterm (≤36 weeks; OR=1.09, 95% CI 0.86–1.37). The risk of preterm birth was not significantly associated with the length of the mother’s exposure to the burn pit or to whether she became pregnant during deployment. Paternal exposure was not significantly associated with preterm births, regardless of the length or proximity of the father’s exposure to a burn pit.
Katon et al. (2017) conducted a retrospective cohort study of Gulf War veterans in 2014. Using data from the National Health Study for a New Generation of U.S. Veterans from the years 2009–2011, samples from 30,000 veterans who were deployed or not deployed to OEF/OIF were examined to evaluate the types of pregnancy outcomes among women who served in OEF and OIF. Live births and pregnancies were reported (nondeployed n=1,295; deployed n=1,773), and among women who had deployed, conceptions and outcomes were classified as occurring before deployment, during deployment, or post-deployment. Only 79 women out of the 3,068 with at least one pregnancy (3%) reported more than five pregnancies. Outcomes included, but were not limited to, preterm birth, low birth weight, and macrosomia. Among the 2,276 pregnancies that resulted in live births, there were 191 preterm births, 153 low-birth-weight infants, and 272 macrosomic infants. After comparing women who were pregnant before deployment with nondeployed women or women who became pregnant after deployment, the researchers found that there was a significantly increased risk of preterm birth among the nondeployed (OR=2.16, 95% CI 1.25–3.72) but not among those who became pregnant after deployment (OR=1.90, 95% CI 0.90–4.02). There was no association between deployment and low birth weight or macrosomia. Thus, deployment was not associated with the three adverse pregnancy outcomes in this study.
Ryan et al. (2011) reported that, based on DoD Birth and Infant Health Registry data for 2002–2005, of 63,053 infants born to U.S. military women during that period, 2,941 infants were born to female service members who were deployed at some time during their first trimester of pregnancy. Compared with infants born to women who had deployed prior to or post-pregnancy, infants born to women who had deployed while pregnant were not at an increased risk of preterm birth (OR=1.13, 95% CI 0.97−1.32) or extreme preterm birth (≤28 weeks; OR=1.11, 95% CI 0.73−1.68). Women who were deployed during their first trimester of pregnancy were not at an increased risk of having an infant with a birth defect compared with women who had deployed at any time other than the first trimester (OR=1.14, 95% CI 0.93−1.40).
A study by Shaw et al. (2018) extracted data from the Stanford Military Data Repository on 12,877 deliveries to U.S. Army soldiers who had children between 2011 and 2014. The prevalence of spontaneous preterm birth was twice the rate among female soldiers who delivered within a 6-month period after returning from deployment than among women who had longer post-deployment intervals before delivery (OR=2.1, 95% CI 1.5–2.9). This finding was interpreted by the authors to suggest that women in service should postpone conception for longer than 6 months after returning from deployment.
The 2011 Institute of Medicine (IOM) committee that assessed the long-term health consequences of exposure to burn pits in Iraq and Afghanistan did not find any evidence for health effects in veterans who had been exposed during deployment. However, the committee referred to an earlier Gulf War and Health (IOM, 2005) report on combustion products from the burning of fuel that reported an association with (unspecified) reproductive effects. Further assessment of exposure to burn pits and birth outcomes was conducted by Conlin et al. (2012), who also used the DoD Birth and Infant Health Registry to identify live infants born to deployed men or women between 2004 and 2007. There was no increase in the risk of being diagnosed with a birth defect within the first year of life for infants born to active-duty women regardless of whether the women were within a 3-mile radius of a burn pit (OR=1.18, 95% CI 0.85–1.63), the cumulative deployment length, or whether they were pregnant while exposed. Nor was there an association between birth defects and paternal exposures to the burn pits.
The association between adverse birth outcomes among U.S. Navy women and occupational and environmental exposures for either the mother or the father was explored by Hourani and Hilton (2000).
Compared with the children of civilian beneficiaries, children born to active-duty women and whose fathers had exposure to chemicals other than pesticides, heavy metals, or petroleum products at home or at work were at an increased risk for birth defects (home OR=8.4, 95% CI 2.18–32.09, and work OR=3.4, 95% CI 1.35–8.82); maternal exposure was not associated with birth defects.
Synthesis and Conclusions
Only two studies of female reproductive effects were identified by the committee. One study assessed the long-term health of service members who were deployed and found that there were no increased risks of having a miscarriage on the basis of military service or deployment alone. Only one study reported on self-perceived fertility, and it also found no association with deployment. There were no studies of male reproductive effects.
The Volume 11 committee identified five studies that examined the association between deployment of women and adverse pregnancy outcomes. Three of the studies found no significant association between deployment exposures and the risk of a female veteran having a preterm or low-birth-weight infant (Conlin et al., 2012; Katon et al., 2017; Ryan et al., 2011). One study found an association between exposure to petroleum products around the home and an increased risk of having a low-birth-weight infant among female U.S. Navy veterans compared with civilian beneficiaries, but the exposures were not related to deployment. Shaw at al. (2018) found an increase in the risk of preterm birth for women who gave birth within 6 months of returning from deployment compared with those who had a child later. None of the studies found an association between a father’s deployment exposure and any adverse pregnancy outcomes. It is difficult to interpret these studies because of the variability in the duration and nature of the exposures and the outcomes that were assessed.
The Volume 11 committee concludes that there is inadequate/insufficient evidence to determine whether an association exists between deployment and reproductive effects in men or women, or with adverse pregnancy outcomes.
The Volume 11 committee identified two studies of developmental effects and deployment exposures. Conlin et al. (2012) found no association between mothers’ or fathers’ exposures to burn pits during deployment and birth defects in their children. A second study found an association between some parental environmental exposures and birth defects, but the exposures were not deployment-specific.
The Volume 11 committee concludes that there is inadequate/insufficient evidence to determine whether an association exists between deployment and developmental effects.
Several chemicals used for tactical purposes during the Gulf War were identified by P.L. 105-368 and P.L. 105-277, including the nerve agents sarin and tabun and the vesicant agent sulfur mustard. The Gulf War legislation specified chemical warfare agents that veterans may have been exposed to during their deployments to the Persian Gulf: that is, sarin/cyclosarin, tabun, and mustards. Because few data have been available for review regarding tabun, previous Gulf War and Health committees have not reviewed or made conclusions pertaining to it. No new information on possible exposures to tabun during the Gulf War or Post-9/11 conflicts is available. No literature on any reproductive or developmental health effects of tabun or sarin/cyclosarin were identified in the Volume 11 committee’s literature search; new literature for other agents was examined. Background information was derived from earlier reviews of these agents as summarized in volumes 1 and 4 (IOM, 2000, 2006a). The studies used by the committee to reach its conclusions on chemical warfare agents are summarized in Table 4-1 at the end of this section.
Sarin and cyclosarin are highly toxic nerve agents used for chemical warfare. These agents were first manufactured in 1937 in Germany for use as insecticides. However, they were not used in warfare until the Iran–Iraq conflict in the 1980s (IOM, 2000). Sarin is a member of a class of chemicals known as organophosphorus esters (or organophosphates), and it is structurally similar to the drug PB (IOM, 2000).
As reported in Gulf War and Health, Volume 4 (IOM, 2006a), during a cease-fire period in March 1991, troops from the US 37th and 307th engineering battalions destroyed enemy munitions throughout the occupied areas of southern Iraq, including at a large storage complex at Khamisiyah, which contained more than 100 bunkers. Two sites in the complex—1 bunker and a pit—contained stacks of 122-mm rockets loaded with sarin and cyclosarin. When these were detonated, an estimated 371 kg of sarin and cyclosarin combined were released (Winkenwerder, 2002). U.S. troops performing the demolitions were unaware of the nerve agents because their detectors, sensitive only to lethal or near-lethal concentrations of nerve agents, did not sound any alarms before demolition. It was reported that soldiers who experienced high levels of exposure had symptoms such as tightness of the chest, watery eyes, and muscle twitching. If the estimated dose was less than what would be needed to generate visible effects, it was considered a “low exposure.” The Central Intelligence Agency and DoD used models to estimate ground-level concentrations of sarin and cyclosarin as a function of distance and direction from the detonation sites and used those to estimate the extent of potential exposure of U.S. military personnel to the nerve agents. The models suggested that nearly 10,000 U.S. troops were potentially exposed to these nerve agents within a 25-km radius of Khamisiyah (CIA–DoD, 1997; IOM, 2000).
The effects of sarin and cyclosarin exposure during the Gulf War were reviewed in Volume 1 and later updated in 2004 (IOM, 2000, 2004). The analyses centered on the mechanisms and effects of acetylcholinesterase inhibition and neurologic outcomes, and reproductive effects were reported in animal studies. Thus, neither committee made any conclusions regarding sarin/cyclosarin exposure and reproductive or developmental effects in humans (IOM, 2000, 2004). The Volume 1 committee concluded that although there was “sufficient” evidence that sarin is capable of causing acute-cholinergic syndrome within hours of exposure that resolves within months, there was “limited/suggestive” evidence that there is a relationship between sarin exposure and long-term health effects at the concentrations encountered in theater. Finally, at low doses of sarin not sufficient to cause acute-cholinergic signs and symptoms, there was “inadequate/insufficient” evidence to determine long-term health effects.
After a comprehensive literature search, the Volume 11 committee found no further specific information on exposures of Gulf War or Post-9/11 service members to sarin or cyclosarin during deployment or on any resulting health effects.
Synthesis and Conclusions
The Volume 1 committee did not find evidence for an association between sarin/cyclosarin and reproductive and developmental effects on the basis of animal data; human data were not available. However, there are chemical similarities between these chemicals and organophosphates. The available animal data centered on the mechanisms and effects of acetylcholinesterase inhibition and neurologic outcomes. No further chemical-specific animal or human data were found to inform conclusions regarding sarin, cyclosarin, or tabun and reproductive and development effects. No data were found on reproductive or developmental endpoints related to sarin/cyclosarin exposure.
The Volume 11 committee concludes that there is inadequate/insufficient evidence to determine whether an association exists between exposure to sarin/cyclosarin and reproductive or developmental effects.
Sulfur mustard, also known as a mustard gas agent, was used in World War I. This agent can exist in the form of a vapor, liquid, or solid. Military personnel can be exposed to sulfur mustard through inhalation, dermal contact, or drinking contaminated water. Although mustard agents were identified by Congress as a chemical exposure of concern (P.L. 105-368 and P.L. 105-277), the committee found limited information on Gulf War or Post-9/11 veterans exposed to mustard gas during their deployments. However, there is a September 2016 report in the popular press describing a shell containing sulfur-mustard blistering agent landing at a military base in northern Iraq where U.S. military advisers were helping Iraqi forces against the Islamic State militants (Phippen, 2011). There was little reported exposure to mustards during the Gulf War (PAC, 1996, cited in IOM, 2004), and these agents were not reviewed by previous committees. Because it remains unclear to the committee whether exposure to mustard agents occurred after 1991 in the Persian Gulf region or during the Post-9/11 conflicts, the Volume 11 committee reviewed the literature on mustard agents below.
Sulfur mustard was reviewed in 2003 by the Agency for Toxic Substances and Disease Registry (ATSDR). The long-term effects of exposure to sulfur mustard among Iranian survivors of chemical attacks included reduced sperm counts, increased rate of fetal deaths, and altered sex ratios among the offspring. The scarring of genital tissue from direct contact with sulfur mustard was reported to affect reproductive ability. ATSDR noted that the animal data supported the long-term effects observed in humans, including sperm abnormalities, early fetal resorptions, preimplantation losses, and decreases in live embryo implantations associated with male exposure. The limited data available pertaining to developmental outcomes were equivocal, and no conclusions were made (ATSDR, 2003).
Reproductive Effects in Men and Women
The Volume 11 committee examined a study of sulfur mustard effects on Iranian civilians and the Iranian military. Chronic infertility was evaluated in a historical cohort of sulfur-mustard-exposed veterans originally registered in 1990 with mild to severe injuries in the Hamadan province in Iran (Amirzargar et al., 2009). In 2005, semen, fecundity, and follicle-stimulating hormone (FSH) levels were measured in 64 exposed men and 64 veterans with injuries but with no sulfur mustard exposure. At the time of exposure, the mean age was 24.3 years, and a median of 19 years had elapsed since exposure. Male factor infertility was diagnosed in 14 (22.6%) exposed and 3 (4.9%) unexposed subjects (p=0.007). Ejaculate volume, sperm concentration, and total sperm count were significantly reduced (p<0.01 or 0.001) in the exposed group compared with baseline values obtained in 1990 or to unexposed controls. Out of all semen indices, sperm motility was the only one not affected. FSH was significantly lower (p<0.05) in the exposed group than in unexposed controls, but there were no differences between the groups in the levels of luteinizing hormone (LH) or testosterone.
Testicular effects were evaluated in infertile male Iranian service members who had been exposed to mustard gas in the 1985–1988 Iran–Iraq war (Safarinejad, 2001). Injury from exposure was characterized as severe (n=44), moderate (n=20), or mild (n=17) based on the effects on skin, eyes, mouth, respiratory tract, and lungs from the medical record. Semen parameters and hormone levels were evaluated in all participants, and testicular biopsies were taken from 24 individuals. Reference values were used for comparison. FSH was found to be increased in the severely injured group, but no differences were found for LH and testosterone. Of all participants, 42.5% had azoospermia and 57.5% had oligospermia, with all azoospermic men grouped in the severely injured group. Sperm count, motility, and normal morphology were decreased in all groups as compared to reference values, with the most pronounced effects seen in the severely injured group; statistical analyses were not performed. Biopsies showed seminiferous tubules devoid of spermatogonia, intact Sertoli cells, and normal Leydig cells.
The sperm chromatin structure was analyzed in a second study of veterans of the Iraq–Iran war with sulfur mustard exposure (Safarinejad, 2010). Semen and blood samples were collected from groups of 66 to 68 exposed-infertile, exposed-fertile, unexposed-infertile, and unexposed-fertile men. Exposure was categorized as mild, moderate, or severe based on medical records of the injuries. Sperm DNA was evaluated by a sperm chromatin structure assay. Mean serum LH, thyroid stimulating hormone, prolactin, and testosterone levels were similar between the groups, while mean FSH was significantly higher in both exposed groups and in the unexposed-infertile group than in the unexposed-fertile group (p=0.01). Ejaculate volume was not different among the groups. Other semen parameters (total sperm/ejaculate, sperm concentration, % motile, and % normal) were significantly lower in both exposed-infertile (p=0.001) and exposed-fertile (p=0.01) groups and the unexposed-infertile group (p=0.01) than in the unexposed-fertile controls. The most marked effects on sperm parameters were seen in the exposed-infertile group. The sperm DNA fragmentation index (DFI) was significantly increased in all groups compared with the unexposed-fertile controls (p=0.01), with the greatest difference seen between the exposed-infertile group and the unexposed fertile group (41.6±4.4 versus 21.4±2.3%, Mann-Whitney U-test, p=0.001). Spermatozoa from mustard gas-injured subjects had more (p=0.001) abnormal chromatin (increased mean, standard deviation, and DFI) than spermatozoa from their non-mustard-gas-injured counterparts. An evaluation of semen parameters of the exposed groups based on the severity of injury showed more pronounced effects in the moderately and severely injured fertile and infertile individuals than in those of the mildly injured individuals.
Fertility was evaluated in survivors of a 1991 sulfur mustard attack on Sardasht, Iran (Ghanei et al., 2004). Exposure was verified through medical records with follow-up interviews and physical examinations. Participants were divided into those married for at least 1 year prior to exposure (66 males, 34 females) and those married after exposure (30 males, 12 females). Infertility was defined as a failure to conceive after 12 months of unprotected intercourse after marriage. A total of 115 couples were evaluated, 88 of whom reported that only one partner had been exposed and 27 of whom reported that both partners had been exposed. The infertility rate was 7.5% in couples married before exposure and 10.3% in couples married after exposure (p=0.531).
Adverse Pregnancy Outcomes
A cross-sectional study evaluated adverse birth outcomes in Iraqi civilians after the Gulf War (Arnetz et al., 2013). The cohort included 307 individuals living at that time in the metropolitan area of Detroit, Michigan, who had either lived in Iraq during and after the Gulf War (n=185) or who had left before the war (n=122). Data were collected by structured interview, and respondents were asked about environmental chemical exposures, including nerve gas and mustard gas, and stress exposures. Aggregate chemical and stress exposure scores were calculated for each individual. Overall, the results of self-reported data showed that chemical exposures were positively correlated with adverse birth outcomes (OR=2.04, 95% CI 1.12–3.74). Specifically, an exposure to mustard gas was associated with stillbirth (OR=2.54, 95% CI 1.24–5.23, p=0.013) but not congenital anomalies, low birth weight, or preterm delivery. However, the timing between exposure and birth outcome was not specified.
A study by Abolghasemi et al. (2010) examined congenital anomalies and childhood illness up to age 16 among 498 children of civilian men with confirmed mustard gas exposure in Sardasht City, Iran. Children whose mothers were also exposed were excluded. The 164 couples with the male exposed were age-matched to 136 controls from a nearby city with no history of chemical attack. Demographic and exposure data were collected by interview, and trained general practitioners evaluated the medical histories of all offspring born at least 9 months after the date of paternal exposure, which ensured that the children themselves were not exposed. The overall frequency of abnormalities and disorders in the exposed group was significantly higher than in the nonexposed group (95 [19%] versus 77 [11%]; OR=1.93, 95% CI 1.37–2.72, p<0.001). Respiratory diseases were found in 20 children (4%), and 21 children (4%) had congenital malformations, as compared with 9 (1%) for both endpoints in the nonexposed group. The frequency of respiratory diseases (OR=3.12, 95% CI 1.43–6.80, p=0.004) and of congenital malformations (OR=3.54, 95% CI 1.58–7.93, p=0.002) were both significantly higher in the offspring from the exposed group than from the nonexposed group, but no significant associations were found for specific respiratory conditions or congenital anomalies. No significant differences were observed for any other disorder as coded by ICD-10 categories. The analyses did not control for potential confounding factors. However, the authors concluded that generational effects can occur from exposure to mustard gas. They also concluded that parental exposure to mustard gas may affect fertility and possibly affect children’s health and long-term development.
One animal study relevant for chemical warfare exposures was identified. Nitrogen mustard, like sulfur mustard, is a blistering agent, and it has similar toxicological effects. He et al. (2007) examined the effects of nitrogen mustard on Sertoli cells in vitro. Sertoli cells were isolated from 20-day-old male Kunming mice and cultured with 0, 50, 100, or 200 μmol/L of nitrogen mustard for up to 24 hours. Treated cells showed smaller cell bodies, a disruption of the cytoplasm, and concentration-related significant decreases in length and area (p<0.01 or 0.05). Immunohistochemistry revealed the collapse of vimentin intermediate filaments and a disruption of the network between nuclear and cell membranes. Both messenger ribonucleic acid and protein expression for vimentin were decreased in a concentration- and time-related manner.
Synthesis and Conclusions
Three studies on sulfur mustard found adverse effects on semen parameters in men with exposures sufficient to cause acute effects (Amirzargar et al., 2009; Safarinejad, 2001, 2010). All these studies were conducted on men who had been exposed to sulfur mustard during the Iran–Iraq war in the late 1980s. One study found no association between exposure to sulfur mustard and fertility among Iranian couples where one or both partners were exposed during a chemical attack (Ghanei et al., 2004). Those investigators reported on female fertility following a chemical attack in Iran with sulfur mustard; they found no association.
One study in Iran found a significant association with adverse birth outcomes, specifically for stillbirth but not for congenital anomalies, low birth weight, or preterm delivery (Arnetz et al., 2013). Children born to fathers with prior exposure to sulfur mustard were at a significantly increased risk for respiratory diseases and congenital abnormalities but not for specific diseases or anomalies (Abolghasemi et al., 2010). Although sulfur mustard is a known mutagen, no data were identified to inform conclusions on reproductive or developmental effects.
The Volume 11 committee concludes that there is limited/suggestive evidence of an association between exposure to sulfur mustard and reproductive effects in men.
The Volume 11 committee also concludes that there is inadequate/insufficient evidence of an association between exposure to sulfur mustard and reproductive effects in women, or with adverse pregnancy outcomes.
One study in Iran found an increase in congenital anomalies and childhood illness in children born to parents exposed to mustard gas in Iran (Abolghasemi et al., 2010). The authors concluded that parental exposure to mustard gas can affect fertility and possibly have an impact on children’s health and long-term development.
The Volume 11 committee concludes that there is inadequate/insufficient of an association between prenatal exposure of women to sulfur mustard and developmental effects.
TABLE 4-1 Summary of Reproductive and Developmental Effects of Chemical Warfare Agents
|Reproductive Effects in Men|
|Amirzargar et al. (2009)||Historical cohort study. 64 sulfur mustard-exposed and 64 matched unexposed enrolled in the study of the Iraq–Iran conflict. Reproductive status of exposed and unexposed compared 16–22 years after first injury. Mean ages of 24.3±6.3 years (range 17–40 years).||Sulfur mustard||Semen indices lower in exposed men versus baseline values and unexposed men.
Male factor infertility increased in exposed (22.6%) versus unexposed (4.9%) (p=0.007). FSH higher in infertile men than in exposed men who were fertile (p<0.0001).
This study provided no ORs for the results.
|Ghanei et al. (2004)||115 couples, 88 with 1 partner and 27 with both partners exposed to mustard gas.
Study focused on Sardasht, a Kurdish Iranian town. Occurrence of infertility evaluated as failure to conceive after 12 months of unprotected intercourse.
|250-kg bombs containing liquid mustard gas released from an aircraft near the city exposing 4,500 civilians to various levels of the toxin.||7.5% rate of infertility was observed among couples who were married at the time of exposure.
Infertility rate of 10.3% was noted among individuals single at exposure and subsequently married.
Overall infertility rate of 8.3%, compared with a worldwide rate of 10–15%.
Using the Fisher exact test, results showed no significant differences among fertility groups 1 and 2 (p=0.531).
This study provided no ORs for the results.
|Safarinejad (2001)||81 Iranian men divided into three groups (44 severely injured men, 20 moderately injured men, and 17 mildly injured men). Ages ranged from 28 to 41, with a mean age of 34.7 years.||Mustard gas exposure during an attack in the 1985–1988 Iran–Iraq War, and some exposed in a contaminated area several hours after the attack.||Azoospermia and severe oligospermia diagnosed in (34) 42.5% and (47) 57.5% of subjects.
This study provided no ORs for the results.
TABLE 4-1 Continued
|Safarinejad (2010)||268 Iranian subjects: Group 1—66 subjects were mustard gas-injured infertile men ages 37 to 55; Group 2—68 subjects were non-mustard-gas-injured fertile men ages 39 to 57; Group 3—68 subjects were non-mustard-gas-injured infertile men who also had oligoasthenoteratozoospermia (ages 35 to 55); and Group 4—66 subjects were non-mustard-gas-injured normozoospermic fertile control men ages 35 to 55.||Mustard gas||The sperm DNA fragmentation index was significantly increased in all groups compared with the unexposed-fertile controls, with the highest value in the exposed-infertile group. Evaluation of semen parameters of the exposed groups based on severity of injury showed more pronounced effects in the moderately and severely injured infertile (41.6±4.4%; p=0.01) and non-mustard-gas-injured infertile individuals (35.8±4.5%; p=0.01) compared with those of the mildly injured individuals. This study provided no ORs for the results.|
|Adverse Pregnancy Outcomes|
|Arnetz et al. (2013)||Random cross-sectional sample of 307 Iraqi families in Detroit, MI. Two groups: those in Iraq during the Gulf War (n=185) and those who left Iraq before (n=122).||Chemicals: depleted uranium, smoke from oil-burning fires, pesticides, nerve gas, contaminated food, prenatal exposure to sulfur/nitrogen dioxide.
Aggregate chemical and stress exposure scores calculated for each individual.
|Chemical exposures were positively correlated with adverse birth outcome (OR=2.04, 95% CI 1.12–3.74). Exposure to mustard gas was significantly associated with stillbirth (OR=2.55, 95% CI 1.24–5.23, p=0.013).
Exposure to burning oil pits and mustard gas increased the risks for specific adverse birth outcomes 2 to 4 times.
|Abolghasemi et al. (2010)||Case-control study.
164 couples in Sardasht City, Iran.
164 age-matched controls from a nearby city with no history of chemical attack.
Physical abnormalities evaluated in children of fathers who had been exposed.
|Sulfur mustard||The overall frequency of abnormalities in the exposed group was significantly higher than in the nonexposed group (95 [19%] versus 77 [11%]; OR=1.93, 1.37–2.72, p<0.001). In offspring from exposed fathers, respiratory diseases were found in 20 (4%) subjects, and 21 (4%) had congenital malformations, compared with 9 (1%) for both endpoints in the nonexposed group. Frequency of respiratory diseases (OR=3.12, 95% CI 1.43–6.80, p=0.004) and congenital malformations (OR=3.54, 95% CI 1.58–7.93, p=0.002) were significantly higher in the offspring of the exposed group vs the nonexposed group.|
NOTE: CI=confidence interval; DNA=deoxyribonucleic acid; FSH=follicle-stimulating hormone; OR=odds ratio.
Several infectious agents that U.S. service members may have come in contact with during their deployment to the Persian Gulf were identified by P.L. 105-368 and P.L. 105-277, including leishmaniasis. Malaria is also endemic to Afghanistan and was common in Iraq, although it has been eliminated there in recent years (WHO, 2016). The following section discusses these agents because they may exert long-term health effects as described in Gulf War and Health, Volume 5 (IOM, 2007). That volume characterized the long-term adverse health outcomes associated with infection by the following pathogens: Brucella species (spp.), the cause of brucellosis; Campylobacter spp., nontyphoidal Salmonella spp., and Shigella spp., which cause diarrheal disease; Coxiella burnetii, the cause of Q fever; Leishmania spp., the cause of leishmaniasis; Mycobacterium tuberculosis, the cause of tuberculosis; Plasmodium spp., the cause of malaria; and West Nile virus, the cause of West Nile fever. The literature search included studies published through January 2005 and included infections relevant to the Post-9/11 population of veterans. The Volume 5 committee noted that orchioepididymitis may occur in up to 20% of men with brucellosis (Ibrahim et al., 1988; Memish and Venkatesh, 2001; Navarro-Martinez et al., 2001; Papatsoris et al., 2002). It is most often unilateral and accompanied by normal urine sediment (Navarro-Martinez et al., 2001). The Volume 5 committee found that there was sufficient evidence of an association between brucellosis and orchioepididymitis.
Among the infectious diseases listed in P.L. 105-277 and P.L. 105-368, Escherichia coli and sand fly fever were not included in Volume 5 for in-depth evaluation because they did not satisfy the criteria for determining the strength of an association between the primary infection and a health outcome in humans. E. coli, in particular, is ubiquitous in nature, making it challenging to distinctly identify effects unique to military personnel. Shigellosis, one of the infectious diseases also listed in the legislation, was not exhaustively discussed in Volume 5 because of the lack of relevant information available on the veteran cohorts of interest.
In the present volume, the committee identified several new studies describing relevant sequela of leishmaniasis. No new data were identified for the other infectious agents of concern. The studies used by the committee to reach its conclusions on infectious agents are summarized in Table 4-2 at the end of this section.
Leishmaniasis is an all-inclusive term for various manifestations of sand-fly-borne parasitic disease, such as cutaneous leishmaniasis, diffuse cutaneous leishmaniasis, mucocutaneous leishmaniasis, visceral leishmaniasis, and viscerotropic leishmaniasis (see IOM, 2007, for a description of the varieties of leishmanisasis). This infectious disease occurs in tropical and temperate climates. Veterans can be exposed to this disease through sand flies, which act as vectors that inject the parasite into humans (IOM, 2007). The infection manifests as skin lesions and damage to internal organs such as the heart, liver, and spleen. Congenital transmission of leishmaniasis from pregnant mother to child has been documented, with transplacental transmission being suspected. In addition to the damage done by direct infection of the child, animal studies suggest that the mother’s immune response may also be responsible for adverse birth outcomes (Berger et al., 2017). The Volume 11 committee did not identify any studies of developmental effects in children following prenatal or preconception exposure to leishmaniasis.
Infectious agents such as leishmaniasis plagued U.S. troops deployed to OEF/OIF. Both published reports and presentations available to the public indicate that more than 1,000 U.S. service members
received a diagnosis of leishmaniasis contracted during their deployments (IOM, 2007). Three new studies published since the 2007 review were identified: two studies of leishmaniasis in pregnant women and one animal study.
A cross-sectional study of pregnant women diagnosed with visceral leishmaniasis was conducted by Adam et al. (2018). The study was carried out from January 1, 2014, to December 31, 2015, at Gadarif Hospital in Sudan. Demographic and obstetric data were recorded, along with the time span between the onset of visceral leishmaniasis symptoms and hospitalization. Of 45 women, 6 died during pregnancy, and 2 died after delivery. Of the remaining 37 patients who were followed until delivery, 30 (77%) had full-term deliveries with a live neonate who had no observable health issues upon delivery, 6 experienced preterm delivery, 2 had a spontaneous abortion, and 1 had a stillbirth. The authors concluded that visceral leishmaniasis has a very high case fatality rate during pregnancy.
Case reports were described for five women in Brazil who were treated for visceral leishmaniasis during pregnancy (Figueiro-Filho et al., 2008). The women were between 16.5 and 36 weeks of pregnancy at presentation, and the disease was confirmed by positive antibody testing and a demonstration of amastigote forms of leishmania in bone marrow. All patients presented with fever, splenomegaly, and hepatomegaly. One patient died due to hemorrhage after delivery as a result of low platelet count. Treatment with amphotericin B was successful, and no vertical transmission was found. All infants were reported to be healthy at birth. At the 1-year follow-up, the infants and mothers were considered healthy and free of disease.
A study by Avila-Garcia et al. (2013) discussed the transplacental transmission of cutaneous Leishmania in mice. Transplacental transmission of the parasite from an infected mother to the fetus has been documented in humans with L. chagasi, which causes visceral leishmaniasis (Figueiro-Filho et al., 2004), and in mice with L. Mexicana, which causes cutaneous leishmaniasis (Avila-Garcia et al., 2013). In the mouse model, infected dams had increased fetal deaths and resorptions. Importantly, both mother and infected infant can be successfully treated (Figueiro-Filho et al., 2004, 2008).
Synthesis and Conclusions
The Volume 5 committee concluded that there is sufficient evidence of an association between leishmaniasis and acute clinical syndrome. That committee did not identify any new data for most agents concerning reproductive and developmental outcomes, with the exception of the study by Adam et al. (2018) showing that Sudanese women who had leishmaniasis during their pregnancy had an elevated risk of having a high fatality rate for their fetuses and infants. Congenital transmission has been documented with leishmaniasis, which can be successfully treated. Results from animal studies provide additional support for a relationship between adverse birth outcomes and maternal immune response to infection (Berger et al., 2017). No data were available on developmental effects.
The Volume 11 committee concludes that there is inadequate/insufficient evidence to determine whether an association exists between exposure to leishmaniasis and reproductive or developmental effects.
The Volume 11 committee also concludes that there is sufficient evidence of an association between leishmaniasis infection during pregnancy and adverse pregnancy outcomes.
TABLE 4-2 Summary of Reproductive Effects of Infectious Diseases
|Adam et al. (2018)||Cross-sectional study on 45 pregnant women in Sudan.||VL||Some women had full-term deliveries (77%) of children with no health conditions, and other women had preterm deliveries (15%) and stillbirths (2%).
Using univariate analyses, maternal mortality among women with VL among those who had a 1-month time span between their symptoms and onset of hospital presentation: OR=6.2, 95% CI 2.8–13.4; p=0.000.
|Figueiro-Filho et al. (2004)||Literature review||VL||VL during pregnancy can be vertically transmitted to the fetus. This is a literature review that provided no ORs.|
|Figueiro-Filho et al. (2008)||Women admitted to the gynecology–obstetrics service at Federal University of Mato Grosso do Sul, Brazil, from January 2004 to December 2005. 5 cases of pregnant women treated for VL.||VL||VL treatment prevented vertical transmission, even in women who were treated after giving birth.
1 patient with a late diagnosis died.
NOTE: CI=confidence interval; OR=odds ratio; VL=visceral leishmaniasis.
The administration of vaccines to Gulf War military personnel is described and reviewed in Gulf War and Health, Volume 1 (IOM, 2000). The U.S. military conducts a comprehensive immunization program designed to protect the members of the armed forces against potential disease risks encountered during service. A standard set of vaccinations is required for each military recruit, which varies slightly by branch of service. Additionally, troops assigned to duty stations are given vaccinations that are specifically targeted to protect them from the risks related to their assignment or endemic to their assigned geographic location.
During the Gulf War, a number of different immunobiologics (e.g., cholera, meningitis, rabies, tetanus, and typhoid vaccines) were used to protect against potential exposures to biological threats. An estimated 150,000 U.S. troops received at least one anthrax vaccination, and an estimated 8,000 individuals were vaccinated with botulinum toxoid. However, medical records from the Gulf War contain little or no information about who received which vaccines, how frequently vaccines were administered, or the timing of vaccinations in relation to the other exposures. Furthermore, existing record entries show no consistency in recording the type of vaccine (notations include “A-Vax,” “Vacc A,” “Vacc B,” and “B Vaccination”). A report by the Office of the Special Assistant for Gulf War Illnesses found that documents from the Gulf War indicate uncertainty about where, or whether, the vaccinations were to be used (OSAGWI, 1999).
Vaccinations were used in the Post-9/11 conflicts to aid in preventing communicable or infectious diseases among deployed troops. Vaccinations became so routine that troops would be vaccinated en masse before deployment (IOM, 2000).
Vaccine-related issues of concern to Gulf War veterans, including the safety of anthrax vaccine, botulinum toxoid vaccine, and issues of multiple vaccines, were discussed by the Volume 1 committee (IOM, 2000). Few peer-reviewed, long-term studies focused on the adverse effects of any of these vaccines were available. Even considering other data (not peer-reviewed or published), there was limited information concerning long-term adverse events. Thus, the Volume 1 committee concluded that there was inadequate/insufficient evidence to determine whether an association exists between long-term adverse effects and any of the exposures of interest.
Regarding the anthrax vaccine, the Volume 1 committee noted the lack of human data on adverse events and the lack of long-term monitoring for such effects. No significant adverse events had been reported at that time, leading the Volume 1 committee to conclude that there was inadequate/insufficient evidence to determine whether an association does or does not exist between anthrax vaccine and long-term adverse health effects. The Volume 1 committee encouraged continued investigation and publication of such data.
The Volume 1 committee found that the available data for the anthrax vaccine were sparse and provided no convincing evidence that personnel who received anthrax vaccine had elevated risks of later-onset health events. That committee made many recommendations to DoD and other agencies to support a safe vaccine surveillance program (IOM, 2000). The studies used by the committee to reach its conclusions on vaccines are summarized in Table 4-3 at the end of this section.
Reproductive Effects in Women
The Volume 11 committee identified several studies on anthrax vaccine published after Volume 1, including three epidemiologic investigations in military populations, a review of adverse events following
the use of the anthrax vaccine, one study in rabbits, and one study of the vaccine in conjunction with smallpox vaccine during pregnancy. No new data on any other vaccines of concern were identified.
Adverse events following anthrax vaccination as reported to the Vaccine Adverse Event Reporting System (VAERS), a national spontaneous reporting system used to monitor the safety of vaccines in the United States from January 1998 through December 2001 were reviewed by Sever et al. (2004). VAERS is a passive surveillance system jointly administered by the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention. During the study interval, 3,991 adverse events were recorded or 9.4 reports/10,000 doses of anthrax vaccine or 1 event/282 vaccines. Flu-like symptoms, rash, malaise, arthralgia, and headache were the most prevalent adverse events reported. Reproductive system adverse events included two spontaneous abortions and one trisomy 13, which could not be attributed to vaccination.
The effects of anthrax vaccination on semen parameters and pregnancy rates were evaluated in couples seeking assistance at the Walter Reed Army Medical Center Assisted Reproductive Technologies Program (Catherino et al., 2005). Data on 254 vaccinated and 791 unvaccinated men were collected by interview. The mean age of the men in the two groups was similar, and the average ages of the men and the women in the two groups ranged from 34.8 to 35.9. Self-reports of tubal factor infertility were significantly more common among exposed men compared with unexposed men (48% versus 35.2%; p<0.01), whereas male factor infertility was significantly lower for exposed men versus unexposed men (19.4% versus 28.2%; p<0.01). However, there was no significant difference in 5-day embryo transfers performed on the female partners of the exposed versus unexposed men (20.9% versus 14.5%; p=0.507). There were no significant differences in semen parameters—including the mean concentration, total motile concentration per sample, and morphology—between the vaccinated and the unvaccinated men. Fertilization rates and embryo quality were not affected by vaccination. Nor were the pregnancy rates for the vaccinated and unvaccinated groups significantly different (49.6% and 45.9%, respectively).
Wiesen and Littell (2002) evaluated the effect of anthrax vaccination on pregnancy rates, fetal loss, and birth outcome among 3,136 vaccinated and 962 unvaccinated U.S. Army women (ages 17–44). Individual data were obtained from administrative and clinical databases, and the analyses were adjusted for age, marital status, and race. All vaccinated women had received at least one dose of anthrax vaccine, and a majority had been given 2–3 doses. No attempt was made to evaluate a dose–response relationship. In the vaccinated and not-vaccinated groups the annualized pregnancy rates were 159.5 and 160.0 per 1,000 person-years, respectively. No associations were found between anthrax vaccination and pregnancy, birth rate, or adverse birth outcome. Adjusted ORs were 0.94 (95% CI 0.8–1.2) for pregnancy, 0.9 (95% CI 0.5–1.4) for birth rate, and 1.3 (95% CI 0.2–6.4) for low birth weight. No significant increase was found for any structural anomaly in the offspring (OR=0.7, 95% CI 0.2–2.3).
Adverse Pregnancy Outcomes
Pregnancy and infant health outcomes were evaluated in U.S. military women who had received the anthrax vaccine (AVA) during pregnancy (Conlin et al., 2015). The women were registered with the National Smallpox Vaccine in Pregnancy Registry because they had received a smallpox vaccine within the 28 days prior to or during a pregnancy. Analyses included 308 women (312 fetuses) vaccinated for anthrax in pregnancy and 155 women (156 fetuses) not vaccinated for anthrax. Outcomes were compared between the anthrax vaccine-exposed group and expected values determined by a literature review, and additional comparisons were made between the anthrax vaccine-exposed and unexposed groups. Infant health outcomes (preterm birth, low birth weight, major birth defects, and male sex of infant) were similar between the AVA-unexposed group (N=125) and the AVA-exposed group (N=271) for preterm
birth (OR=8.8, 95% CI 4.5–15.2 versus OR=10.0, 95% CI 6.7–14.2); low birth weight (OR=9.6, 95% CI 5.1–16.2 versus OR=7.7, 95% CI 4.9–11.6); major birth defects (OR=3.2, 95% CI 0.9–8.0 versus OR=2.6, 95% CI 1.0–5.2); and male sex of infant (OR=52.8, 95% CI 43.7–61.8 versus OR=48.7, 95% CI 42.6–54.8). Adverse fetal outcomes for AVA-unexposed women were higher than or similar to those of AVA-exposed women (ectopic pregnancy: OR=2.6, 95% CI 0.7–6.4 versus OR=0.3, 95% CI 0.0–1.8; elective abortion: OR=7.2, 95% CI 3.7–14.2 versus OR=4.4, 95% CI 2.5–7.9; stillbirth: OR=2.4, 95% CI 0.5–6.8 versus OR=0.7, 95% CI 0.1–2.7). Results were similar when the outcomes among women who received anthrax and smallpox vaccines during pregnancy (not before) were compared with outcomes in women who received the smallpox vaccine during pregnancy and not before.
Conlin et al. (2017) conducted a study to determine if vaccination during pregnancy is associated with the risk of birth defects. Data on 126,839 live infants born in 2003–2010 were obtained from the DoD Birth and Infant Health Registry. Mothers were placed into categories based upon their vaccination exposure and time to pregnancy. The medical records of infants were evaluated for possible birth defect diagnoses that may have occurred within the first year of life. The researchers found that infants born to mothers vaccinated during their first trimester did not have higher risks of birth defects compared with mothers vaccinated at any other time (OR=1.10, 95% CI 0.93–1.29). Infants born to mothers vaccinated before pregnancy had a slightly higher risk of developing a birth defect than infants born to mothers vaccinated after their child’s conception (OR=1.11, 95% CI 1.01–1.22). Mothers who were vaccinated after the start of pregnancy had a 10% lower risk of birth defects in their children compared with mothers who never received the vaccination (OR=0.90, 95% CI 0.83–0.99). There was a slight association observed between pre-pregnancy vaccination or never having been vaccinated and birth defects risk when compared with women who were vaccinated after their pregnancy started.
As discussed in Reproductive Effects in Men and Women, Wiesen and Littell (2002) found no association between anthrax vaccination for U.S. Army women and adverse birth outcomes (OR=0.9, 95% CI 0.4–2.4).
A retrospective cohort was used to evaluate the association between birth defects and anthrax vaccination in the first trimester among all infants born to U.S. female service members between 1998 and 2004 (Ryan et al., 2008). Data on live-born infants and maternal anthrax vaccination were obtained from DoD databases. A total of 115,169 infants born to 95,595 mothers were studied, including 3,465 infants born to mothers who received a vaccination in the first trimester and 938 who were exposed to more than one dose of a vaccine during the first trimester. After adjusting for preterm birth, male infants, and maternal age more than 35 years, the researchers found that infants with first-trimester exposure did not have a significantly increased risk of having a birth defect (OR=1.18, 95% CI 0.997–1.41) compared with infants born to women vaccinated outside of the first trimester. However, infants exposed in the first trimester had significantly increased odds of birth defects when compared with infants born to mothers who had never been vaccinated (OR=1.20, 95% CI 1.02–1.42). The most common defect, atrial septal defect, was found in 58 infants exposed in the first trimester, which was a statistically significantly higher rate than among women vaccinated outside of the first trimester (OR=1.38, 95% CI 1.04–1.82).
Conlin et al. (2017) conducted an analyses using data from 2003 through 2010 from active-duty Reserve, Army, Air Force, Navy, or Marine mothers. This study included 126,839 infants born to military mothers, categorized by the timing of the anthrax vaccination relative to the pregnancy. Data such as deployment status during pregnancy and the administration of other vaccinations were included in multivariable models. In the study population, 33.3% of mothers were vaccinated for anthrax prior to
pregnancy (42,260 women); 3.5% during the first trimester (4,418 women vaccinated during the first trimester); 0.3% during the second or third trimester (423 women vaccinated during the second or third trimester); 19.1% post-pregnancy (24,179 women post-pregnancy); and 43.8% were never vaccinated. Infants born to mothers vaccinated in the first trimester of pregnancy were not at increased odds of a birth defect diagnosis (OR=1.10, 95% CI 0.93–1.29) compared with those whose mothers were vaccinated outside of the first trimester. No increased odds for birth defects were found for vaccination during the first trimester compared with pre-pregnancy, post-pregnancy, or never vaccinated. The infants of mothers who were vaccinated pre-pregnancy had slightly higher odds of birth defects than the infants of women who were vaccinated post-pregnancy (OR=1.11, 95% CI 1.01–1.22), while the infants of those vaccinated post-pregnancy had lower odds than those of never-vaccinated mothers.
One animal study identified by the committee examined reproductive toxicity in rabbits. Female New Zealand white rabbits were given anthrax vaccination twice before they mated and again on either gestational day (GD) 7 or 17 (Franco et al., 2009). No adverse effects were found on mating and fertility indices, natural delivery observation, clinical signs, gross lesions, in utero growth or survival, morphological development, or kit viability. The data on rabbits support the findings in humans that there is little evidence of an association between vaccinations and reproductive and developmental effects.
Synthesis and Conclusions
The U.S. military implements a comprehensive immunization program that is designed to protect the armed forces from potential disease risks. A standard set of vaccinations is administered to each military recruit, including those specifically targeted to protect against risks related to their assignments or found in their assigned geographic location (e.g., Afghanistan). As was the case in previous reviews, only limited data on the adverse effects of any of these vaccines were available to inform conclusions on potential reproductive or developmental outcomes. New information was found only for the anthrax vaccination.
Studies of military personnel given anthrax vaccination found no effects on male or female fertility (Catherino et al., 2005). One study found that female soldiers who received the anthrax vaccine were not at increased risk for adverse pregnancy outcomes (Wiesen and Littell, 2002).
One large cohort of military women showed a nonsignificant increase in the risk of birth defects following first-trimester vaccination with anthrax (Ryan et al., 2008); however, this was not observed in a second study that compared the timing of vaccination during pregnancy with the occurrence of birth defects (Conlin et al., 2017). Conlin et al. did find a slightly increased significant risk of birth defects for infants born to mothers who were vaccinated prior to pregnancy compared with those vaccinated after their pregnancy. Given that women who are deployed may not be aware that they are pregnant in their first trimester and may receive vaccinations during this time, continued investigation and publication of these data are needed and encouraged.
The Volume 11 committee concludes that there is inadequate/insufficient evidence to determine whether an association exists between anthrax vaccination and reproductive or developmental effects.
TABLE 4-3 Summary of Reproductive and Developmental Effects of Vaccines
|Reproductive Effects in Men and Women|
|Catherino et al. (2005)||254 men who reported receiving the anthrax vaccination and 791 men who denied vaccination with their partners seeking assisted reproduction services.||Men underwent semen analysis.||Tubal factor infertility was common among the exposed group (48% versus 35.2%; p<0.01); male infertility was less common (19.4% versus 28.2%; p<0.01).
Anthrax vaccination did not statistically alter fertility in men who were undergoing assisted reproduction. This study provided no ORs for results.
|Wiesen and Littell (2002)||Cohort study from a database of women ages 17–44. Stationed at Fort Stewart, GA/Hunter Army Airfield, GA, from 1999 to 2000.||4,092 women of whom 3,136 received at least one dose of anthrax. 513 pregnancies with 385 following at least one dose of the vaccine.
353 live births and 25 pregnancies lost to follow-up.
|Vaccination had no effect on pregnancy, birth rates, or adverse birth outcomes. When comparing the pregnancy ratio for vaccinated women versus unvaccinated women: OR=0.94, 95% CI 0.8–1.2, p=0.60; birth OR=0.9, 95% CI 0.5–1.4, p=0.55; and adverse birth outcomes OR=0.9, 95% CI 0.4–2.4, p=0.88.
No associations were found between anthrax vaccination and pregnancy, birth rate, or adverse birth outcome. No significant increase was found for any structural anomaly.
|Adverse Pregnancy Outcomes|
|Conlin et al. (2015)||Enrollment began in 2003. 517 U.S. military women were chosen who represented 522 pregnancies. 504 eligible women.||Smallpox/anthrax vaccination. 95% of subjects received one or both vaccines before 8 weeks gestational age.
65% of subjects also reported receiving AVA around the time of the smallpox vaccination.
|Rates of birth defects and preterm birth remained constant with infants born to military mothers since 2003.
Infant health outcomes (preterm birth, low birth weight, major birth defects, etc.) were similar between the AVA-unexposed groups (n=125) and the AVA-exposed group (n=271) for preterm birth (OR=8.8, 95% CI 4.5–15.2 versus OR=10.0, 95% CI 6.7–14.2); low birth weight (OR=9.6, 95% CI 5.1–16.2 versus OR=7.7, 95% CI 4.9–11.6); major birth defects (OR=3.2, 95% CI 0.9–8.0 versus OR=2.6, 95% CI 1.0–5.2); and male sex of infant (OR=52.8, 95% CI 43.7–61.8 versus OR=48.7, 95% CI 42.6–54.8).
Adverse fetal outcomes for AVA-unexposed were higher than or similar to those of AVA-exposed women (ectopic pregnancy: OR=2.6, 95% CI 0.7–6.4 versus OR=0.3, 95% CI 0.0–1.8; elective abortion: OR=7.2, 95% CI 3.7–14.2 versus OR=4.4, 95% CI 2.5–7.9; stillbirth: OR=2.4, 95% CI 0.5–6.8 versus OR=0.7, 95% CI 0.1–2.7).
|Conlin et al. (2017)||126,839 infants born to military mothers during 2003–2010.||AVA||Infants born to mothers vaccinated in the first trimester were not at increased odds of a birth defect diagnosis (OR=1.10, 95% CI 0.93–1.29) compared with those vaccinated outside of the first trimester. No increased odds for birth defects were found for vaccination during the first trimester compared to pre- and post-pregnancy or never vaccinated. Infants born to mothers vaccinated pre-pregnancy had slightly higher odds of birth defects than to mothers vaccinated post-pregnancy (OR=1.11, 95% CI 1.01–1.22).|
|Ryan et al. (2008)||3,465 infants born to women service members between 1/1/98 and 2/21/04. 115,169 infants born to 95,595 military women.||Anthrax vaccine during first trimester; 938 of infants were exposed to >1 dose during the first trimester.
33,675 infants born to women who received the vaccine outside of their first trimester; 663 of those were exposed in late pregnancy.
14,306 infants’ mothers were vaccinated before pregnancy.
18,706 infants’ mothers were vaccinated after birth.
78,029 infants were unexposed.
|Maternal anthrax vaccination in the first trimester is associated with an increased prevalence of birth defects in infants, mainly atrial septal defects (OR=1.38, 95% CI 1.04–1.82).
Women who were vaccinated before pregnancy or in late pregnancy did not have an increased risk of their infants being born with birth defects when compared with women who had not been vaccinated.
|Moro et al. (2017)||Birth defects in children from 50 reports.||Vaccinations (some anthrax).||Results showed that infants born to mothers vaccinated in their first trimester experienced a higher rate of deformities than infants born to mothers who were vaccinated in the second or third trimester.
This was a review of the VAERS database and did not provide ORs for results.
NOTE: AVA=anthrax vaccine absorbed; CI=confidence interval; OR=odds ratio; VAERS=Vaccine Adverse Effect Reporting System.
DU is a by-product of the enrichment process used to make reactor-grade uranium. It is a weakly radioactive, chemically toxic heavy metal that is derived from natural uranium and used by the U.S. military for munitions and for armor on some tanks. It is well suited as a munition because of its high density and “self-sharpening” nature, both of which help it to penetrate armor. Its high density also makes it an effective shield. DU has been used by all branches of the U.S. military since the 1980s, and it has been used on the battlefield in the Persian Gulf War, the Balkans, and the Iraq War (NRC, 2008).
In the Gulf War, DU was frequently used in an effort to increase the protective layer on heavy-armor tanks to prevent penetration by weaponry. Additionally, the U.S. Army used an estimated 9,500 DU tank rounds during the Gulf War, many of them as training and practice rounds as well as in kinetic energy cartridges and ammunition rounds (IOM, 2000). U.S. service members could be exposed to DU through a variety of pathways, including “friendly fire” incidents, ingestion, inhalation, cleanup operations, and accidents (IOM, 2000). Some military personnel were exposed to DU through contact with contaminated vehicles and inhalation of contaminated dust. Level I exposure, the highest level, occurred in or near combat vehicles when they were struck by DU rounds or when soldiers entered vehicles soon after the impact of such rounds. U.S. military personnel may have experienced Level I exposure as a result of wounds caused by DU fragments, inhalation of airborne DU particles, or ingestion of DU residues. Level II, the intermediate exposure level, occurred when soldiers and civilian employees worked on DU-contaminated vehicles or were involved in cleanup efforts at their installations. More than 700 individuals may have had Level II exposure from the inhalation of dust containing DU particles and residue, ingestion from hand-to-mouth contact, or contamination of clothing. Level III, the lowest level of exposure, occurred when troops entered DU-contaminated Iraqi tanks or when they were downwind from burning DU ammunition, DU-contaminated vehicles, or the Camp Doha fire near Kuwait. Level III exposures could have occurred though inhalation or ingestion. Hundreds of people in both military and civilian cleanup crews are thought to have experienced potential Level III exposure, but there is little additional information on these estimates (OSAGWI, 1998).
In the Post-9/11 conflicts, DU was used to armor tanks and help bullets penetrate enemy armored vehicles. Post-9/11 veterans were exposed to DU via the same routes as Gulf War veterans. Most exposures occurred from DU-containing missiles striking vehicles, producing airborne DU-particles that could be inhaled.
The health effects that may result from DU exposure were reviewed in Gulf War and Health, Volume 1 (IOM, 2000) and in an updated review in 2008 (IOM, 2008a). The updated review covered literature through 2007. The committees that produced those reviews relied on studies in nonveteran populations and supporting information from animal studies to establish biologic plausibility. Studies on uranium workers were reviewed, but they carried less weight in the committees’ final conclusions because radon, which is the primary disease-causing exposure in uranium miners, has different physiochemical properties and deposition patterns in the airways than DU and it also lacks the chemical toxicity (as opposed to radiologic toxicity) of DU. Furthermore, uranium miners have a different array of exposures to other toxic dusts and gases, which makes comparisons with veterans of limited value. Both committees concluded that there was inadequate/insufficient evidence of any association between DU and reproductive or developmental outcomes (IOM, 2000, 2008a).
In 2008, a National Research Council (NRC) committee released a review of the available toxicologic, radiologic, epidemiologic, and toxicokinetic data on DU to help describe the risk of health effects to exposed military personnel. That committee found that long-term surveillance of DU-exposed Gulf War veterans had yielded no evidence of reproductive-system dysfunction in males, abnormalities
in sperm, or alterations in neuroendocrine function in the first 14 years after exposure. Nor was there evidence of excess spontaneous abortions, fetal mortality, congenital anomalies, developmental delays, or abnormal infant neurobehavioral difficulties in their offspring. However, animal studies focused on uranium placental transfer. In studies that reported placental uranium transfer, dams were exposed to high doses of uranium (equivalent to about 200 g in a 70-kg person). The NRC committee (2008) recommended that on the basis of available reproductive toxicity and developmental toxicity data, samples of blood, urine, or semen of DU-exposed military personnel should be collected for the measurement of uranium content and signs of abnormal reproductive function in men and women. In addition, the reporting of spontaneous abortions and congenital anomalies should be continued.
In 2013, the ATSDR released Toxicological Profile for Uranium, which included information about DU (ATSDR, 2013). The profile reviewed the human and animal literature through 2013 and found that the preponderance of evidence supported renal toxicity, but the data concerning reproductive effects in humans were limited. Reproductive and developmental effects have been studied in mice and rats, but confirmatory studies are needed. The profile did not provide information on depleted uranium specifically.
The studies used by the Volume 11 committee to reach its conclusions on vaccines are summarized in Table 4-4 at the end of this section.
Reproductive and Developmental Effects
Since the uranium update review concluded in 2007, only one new publication has reported on reproductive effects of embedded DU (McDiarmid et al., 2009). The Volume 11 committee did not identify any new studies on the potential developmental effects of preconception or prenatal exposure to DU in humans.
A systematic review by Asghari et al. (2015) focused on multiple studies that were not of sufficient quality or of the necessary focus to be directly relevant to the committee’s task. The review found that exposure to DU through in vivo and in vitro procedures caused dysfunction of the gonadal endocrine system leading to hormonal alterations, apoptosis through reactive oxygen species, and musculoskeletal, digestive, and cardiovascular malformations in neonates that resulted from impaired antioxidant enzymes that were related to oxidative stress. Several publications have continued to report on the surveillance of a group of Gulf War veterans with embedded DU shrapnel; of these, one has reported on reproductive outcomes (McDiarmid et al., 2009). Even though DU has been isolated in semen samples from Gulf War veterans with embedded fragments of the material (Todorov et al., 2013), no effects of DU on semen characteristics (data not reported), neuroendocrine parameters (data not reported), or genotoxicity measures (hypoxanthine-guanine phosphoribosyl transferase mutation assay and fluorescent in situ hybridization assay; p-values all greater than 0.08) were observed 16 years after the Gulf War (McDiarmid et al., 2009). In a review of this work, McDiarmid and colleagues noted that even though no health condition has been consistently observed, urinary concentrations of DU continue to be high—and stable—more than 20 years later. Because tissue concentrations will accrue with the continued mobilization of embedded DU, health effects may still be expected to occur, and thus, these veterans will continue to be monitored (McDiarmid et al., 2009; NASEM, 2016).
The Volume 11 committee identified ATSDR data and seven animal studies that had appeared since the NRC and IOM reviews published in 2008. A two-generation reproductive toxicity study by Arfsten
et al. (2009) examined the effects that long-term DU implantation may have on the reproductive system of the F0 generation (249 male and 248 female rats) and on the development and survival of the F1 and F2 generations. F0 rats were implanted with DU pellets and mated 120 days later. The researchers found that the implantation of DU did not have any effect on the survival or well-being of the F0 generation, and they observed no gross abnormalities in the F1 and F2 generations.
Feugier et al. (2008) conducted a study with a total of 101 female mice exposed to DU through contaminated drinking water for 49 days. They found that DU did not influence the intensity of ovulation, but it did affect the quality of the oocyte. The proportion of healthy oocytes was significantly reduced by half in each group (p<0.001) from 20 mg/L to 10 mg/L when compared with the control group (healthy proportions=0.537, 0.497, 0.282, and 0.239 in the control, 10 mg/L, 20 mg/L, and 40 mg/L groups, respectively).
Darolles et al. (2010) specifically investigated the effect of DU and enriched uranium on mouse fibroblast cells. After DU treatment (5, 50, or 500 μM), no toxicity or incidence of binucleated cells with one micronucleus (BN-1MN) was detected. However, the study did not have the ability to accurately assess overall uranium genotoxicity. DU had a “low clastogenic effect.”2 Its aneugenic effect was significant and led to a global genotoxic effect equivalent to 12% enriched uranium as assessed by classical cytokinesis-block micronucleus assay (BN-1MN counting).
A study by Hao et al. (2009) investigated 150 male and 150 female 3-week-old hybrid Wistar rats (F0). The rats were exposed to DU through food consumption at doses of 0, 4, or 40 mg/kg/d for 4 months and then mated. F1 rats were exposed to the same doses as their parents for 4 months. Results showed that the uranium content in F1 rats was considerably higher than that in F0 rats in both the kidney and the ovary (p<0.05), with significant differences observed by dose and generation in sperm abnormality rate, comet tail length, marrow cell micronuclei rate, and tailed cell percentage. Overall, F1 rats sustained more damage than F0 rats, emphasizing the genotoxic effects of chronic low-dose exposure to DU.
Hao et al. (2012) conducted a follow-up study that tested two generations of Wistar rats. Rats experienced chronic exposure to DU through feed containing DU at doses of 0 (control), 4 (DU4), or 40 (DU40) mg/kg/d for 4 months prior to mating. The FI generation was similarly exposed to DU in feed from postnatal day 21 until death. After 4 months of exposure, the pregnancy rate, normal labor rate, and survival rate of offspring produced by F1 rats were all drastically decreased in comparison with the control group. The DU40 group experienced the largest decrease, with parameters that had fallen by half to two-thirds, while no adverse effects were evident in F0 rats.
Legrand et al. (2016) studied pregnant female Sprague–Dawley rats exposed to DU through drinking water from GD 1 through lactation. Examination of the rats showed that DU decreased cell death in the cortical neuroepithelium of 13 embryos exposed at 40 mg/L and 120 mg/L and in GD18 fetuses exposed at 120 mg/L without altering the number of apoptotic cells. However, postnatal cell death increased in the dentate gyrus in postnatal day (PND) 0 and PND 5 exposed pups at 120 mg/L and was also related to increased apoptotic cell numbers at PND 5. These results showed that DU exposure during the gestational period and during lactation may cause neurogenesis.
A study by Miller et al. (2010) used male transgenic mice (Big Blue strain C57BL/6 hemizygous mice containing 40 copies of a shuttle vector lacI transgene) and non-transgenic female C57BL/6 mice as subjects. These mice were exposed to DU through implantation and drinking water. Within 1 day of DU exposure via implantation or orally through drinking water, male animals (F0) showed significant uranium accumulation in the kidneys, testes, and femur. Final results showed that F0 fathers who
2Clastogenic effects are visible damage or changes to chromosomes that are virtually microscopic, such as breaks in chromosomes or changes in chromosome numbers.
sustained DU exposure had a significant increase in mutation frequency in their F1 offspring (3.57±0.37 and 4.81±0.43 × 10–5; p<0.001) as compared with controls (2.28±0.31 × 10–5). The mutation frequencies of F1 offspring at low-dose implanted DU (2.71± 0.35 × 10–5) were not notably different from the control levels (2.28±0.31 × 10–5). The results of this study suggest that genomic instability is transmitted from fathers who were exposed to DU to the somatic cells of unexposed offspring.
Synthesis and Conclusions
The effects of DU were reviewed by authoritative bodies (ATSDR, 2013; IOM, 2000, 2008; NRC, 2008), and they concluded that DU was not associated with reproductive or developmental effects. Data published since those reviews show no evidence of reproductive or developmental effects in veterans, although the studies are of male veterans only. Studies in animal models have shown mixed results, with some evidence for male and female reproductive effects and genotoxicity in parents and offspring. The Volume 11 committee did not identify any new studies in humans on the association between exposure to DU and developmental effects.
The Volume 11 committee concludes that there is inadequate/insufficient evidence to determine whether an association exists between exposure to DU and reproductive or developmental effects.
TABLE 4-4 Summary of Reproductive Effects of Depleted Uranium
|Reproductive Effects in Men|
|McDiarmid et al. (2009)||Subset of 35 members of a larger cohort of 77 Gulf War veterans.
Urine uranium concentration and blood uranium concentration tests performed on Gulf War veterans.
|DU—exposed during “friendly fire.” Length of exposure not specified.||16 years after exposure, veterans showed little to no signs of DU-related health issues. Slight changes in bone formation as a result of DU exposure. Subtle changes in renal proximal tubular function between high and low exposure. Some veterans had embedded DU fragments (p=0.4).
This review provided no odds ratios for results.
NOTE: DU=depleted uranium.
PB is a drug that was used during the Gulf War as a prophylactic agent against potential exposure to nerve agents, such as sarin. PB acts by binding to acetylcholinesterase (IOM, 2000) to act as a reversible cholinesterase inhibitor. It was created in 1945 and approved by FDA in 1955 for the treatment of myasthenia gravis.3 FDA also approved an injectable form of the drug known for reversing the effects of some anesthetic formulations. The drug is poorly absorbed after oral administration, and peak plasma levels occur 2–3 hours after oral dosing. The drug is eliminated almost exclusively in the urine (IOM, 2000).
PB was first used as an investigational drug during the Gulf War and was not recommended for routine use. FDA, under a then newly-enacted provisional rule, had granted DoD a waiver from the requirement to obtain informed consent from service members taking this drug. Nonetheless, the rule did not address the record keeping that would accompany the use of an investigational drug. DoD reported that 5,328,710 doses were sent into the field and estimated that approximately 250,000 personnel took at least some PB during the Gulf War. It was supplied as a 21-tablet blister pack, and the prescribed dosage was one 30-mg tablet every 8 hours. Variation in use occurred, however, because it was self-administered and supposedly taken only when ordered by the unit commander (IOM, 2000).
The Volume 11 committee found no specific information on exposures of Post-9/11 service members to PB during deployment.
There are ample data pertaining to the use of PB in therapeutic settings, and many studies have examined PB to determine its possible role in causing Gulf War illness. However, few studies have reported on the long-term effects of PB, particularly its reproductive and developmental effects. Gulf War and Health, Volume 1 concluded that that there is inadequate/insufficient evidence to determine whether an association exists between PB and long-term adverse health effects in military personnel (IOM, 2000).
The Volume 11 committee identified two new publications examining PB’s effects on animal reproductive and developmental outcomes that had appeared since the IOM review in 2000. No new studies in humans were identified by the committee.
One study assessing sperm and testicular changes in animals exposed to a mixture of several toxicants, including PB, that was meant to mirror Gulf War exposures was identified. Male rats were exposed to PB, DEET (N,N-diethyl-meta-toluamide), and permethrin with and without restraint stress for 28 days (Abou-Donia et al., 2003). Stress alone did not influence any of the measured outcomes. The testes of animals exposed to the chemical combination showed histologic abnormalities, including arrested spermatogenesis and seminiferous tubule degeneration, and these effects were enhanced by stress. The authors investigated the causal mechanism and identified it as apoptosis due to an increased expression of two apoptosis-promoting proteins in testicular tissue. This study suggests that exposures such as those experienced by Gulf War veterans may contribute to sperm abnormalities and male infertility; however, the animals in the chemical-plus-stress group gained less weight, suggesting poorer health overall, making interpretation of the findings difficult. Additionally, the results reflect the effects of a mixture, so the effects cannot be attributed to any one component (NASEM, 2016).
Berrios et al. (2015) examined GD 14.5 fetuses removed from pregnant rats. Cultures of rat neural progenitor cells were exposed to up to 300 μM of pyridostigmine over the course of 6 days. Reduced viability was not observed after treatment with 200 μM of pyridostigmine. However, results did show
3Myasthenia gravis is an autoimmune disorder characterized by antibody blockade of the acetylcholine receptor at the neuromuscular junction.
that PB decreased neurite growth, but it did not affect cell differentiation, and there were changes in protein expression. These results indicated that developmental patterns may have been affected.
Synthesis and Conclusions
PB was previously reviewed by the Volume 1 committee (IOM, 2000). New animal data identified by the Volume 11 committee came from experiments in which the animals were exposed to multiple chemicals and stress, thus making it impossible to identify any single agent as the cause of the observed effects. The combination exposure with PB, DEET, and permethrin did show effects on the testes which were exacerbated by stress. In vitro studies showed possible effects on neurodevelopment. Given the scarcity of data and the complexity of combined exposures, the new data make interpretation difficult and prevent the committee from coming to a definitive conclusion.
The Volume 11 committee concludes that there is inadequate/insufficient evidence to determine whether an association exists between exposure to PB and reproductive or developmental effects.
In 2003, about 900 U.S. Army personnel and civilian employees were exposed to sodium dichromate at the Qarmat Ali water treatment facility in Iraq, which was being restored by American contractors under the protection of the U.S. Army. Before U.S. control of the site, sodium dichromate was used to filter and treat water from the Tigris River and to prevent the corrosion of pipes and equipment. Vandalism of the facility resulted in sodium dichromate contamination of some parts of the facility (DoD, 2011).
Sodium dichromate contains Cr6, a known carcinogen which causes lung cancer (IARC, 2012). Cr6 is recognized by the European Chemicals Agency as having mutagenic, reproductive, and sensitization effects (ECHA, 2017).
The U.S. Army Center for Health Promotion and Preventative Medicine conducted follow-up medical surveillance and concluded that symptoms such as irritation of eyes, nose, throat, and lungs and the physical findings among exposed personnel were consistent with exposure to the desert environment and that whole blood chromium levels were not elevated (Ciminera et al., 2016). VA enacted a registry and medical surveillance program that began collecting medical data on these individuals in 2009 in collaboration with a parallel DoD program. The health of these service members through January 2012 was recently described by Ciminera et al. (2016), but no information related to reproductive, developmental, or generational outcomes was reported.
An ATSDR profile summarized the literature on Cr6 through 2012, including its reproductive and developmental effects in humans and animals, and it reported that a sensitive endpoint for Cr6 toxicity is the reproductive effects on male reproductive organs, including decreased sperm count and histopathological change to the epididymis (ATSDR, 2012). Because there is a large evidence base regarding the effects of Cr6, the Volume 11 committee focused its review on studies that were not included in the ATSDR review. The committee’s literature search identified 11 epidemiologic studies and 8 animal studies on the reproductive or developmental effects of chromium exposure. The studies used by the committee to reach its conclusions on Cr6 are summarized in Table 4-5 at the end of this section.
Several studies reported on molecular changes associated with chromium exposure. Ali et al. (2011) examined a series of lung cancer cases in chromate workers and found that an individual’s methylation of DNA APC, hMLH1, and MGMT genes was related to the number of years worked in the industry.
Among a small cohort of steel plant workers exposed to chromium, Bollati et al. (2010) found that two micro RNAs (miRNAs) in peripheral blood leukocytes (miR-21 and miR-146a) were not related to chromium exposure, but that miR-222 expression was associated with chromium (β=0.26, 95% CI 0.0–0.58, p=0.05).
The Volume 11 committee identified two new reviews of epidemiologic studies. No epidemiologic studies examined exposure during the preconception or early pregnancy window or effects in veterans. The committee’s search identified several recent studies and one older study that were not considered in the ATSDR profile. Specifically, the committee found three studies of the occupational exposure of men (Ali et al., 2011; Bollati et al., 2010; Yang et al., 2013) and eight studies of environmental exposure: two of which examined Cr6 as a component of air pollution in the United States (Heck et al., 2013; Roberts et al., 2013); three of which studied communities surrounding e-waste recycling operations in China (Guo et al., 2010; Li et al., 2008; Ni et al., 2014); one of which was a study of residents near a factory that used—and emitted—Cr6 (Remy et al., 2017); one of which examined the effects of contaminated drinking water (Aschengrau et al., 1993); and one of which observed Gaza residents exposed to metals, including chromium, as a result of military attacks (Manduca et al., 2014). Many of these studies are confounded by multiple chemical exposures.
Reproductive Effects in Men and Women
An ATSDR (2012) profile summarized the literature on Cr6 through 2012. ATSDR reported reproductive effects in humans associated with occupational exposures, including increased numbers of morphologically abnormal sperm, decreased sperm count and motility, and greater incidences of complications during pregnancy and childbirth (toxicosis and postnatal hemorrhage).
The reproductive impacts of chromium were assessed in one study with a large U.S. population. Residents near a factory in Willits, California, that used Cr6 had greater rates of genitourinary conditions, neoplasms (men and women), and adverse reproductive organ conditions in women (pelvic inflammatory disease, endometriosis, menstrual disorders, ovarian cysts, and reproductive organ surgeries) than compared with the rest of the county and the overall population in California (Remy et al., 2017). Given the large number of subjects and assessments before and after the factory closed, the study authors concluded that chromium was significantly associated with adverse reproductive effects in women. In a meta-analysis of Chinese studies (exact number of studies not given) by Yang et al. (2013), women with occupational Cr6 poisoning were found to have significantly elevated risks of spontaneous abortion (OR=2.31, 95% CI 1.25–4.27) or threatened abortion (OR=20.47, 95% CI 2.60–161.44).
Adverse Pregnancy Outcomes
The Volume 11 committee identified several recent publications and one older one that assessed both pregnancy outcomes and development effects following exposure to chromium. The committee notes that in all cases, pregnant women were exposed to more than one heavy metal or other toxicant. Among pregnant women exposed to contaminated community drinking water in Massachusetts and compared with 1,177 unexposed women, stillbirths (n=77; OR=1.2) and neonatal deaths (n=55; OR not calculated) were not significantly associated with chromium levels in drinking water (Aschengrau et al., 1993). Guo et al. (2010) found no differences in birth length, weight, and gestational age related to placental
chromium levels in infants born to mothers residing near e-waste recycling areas in China (all p>0.7). There was no significant association (p=0.53) between chromium load in the hair of 48 infants born with birth defects and 12 infants born without defects in 2011 whose parents were exposed to metals in Gaza as a result of military weapons in 2009; nor was there a significance difference in chromium load in the hair of 9 infants born prematurely and 12 full-term infants (p=0.8) (Manduca et al., 2014). However, children born to mothers residing near a factory in Willits, California, that used Cr6 had significantly higher rates for short gestation (preterm), low birth weight, or small for gestational age (relative risk [RR]=1.14, 95% CI 1.05–1.25); macrosomia (large for gestational age; RR=1.16, 95% CI 1.04–1.29); perinatal jaundice (RR=1.13, 95% CI 1.06–1.20); and conditions affecting the nervous/sensory system (RR=1.17, 95% CI 1.05–1.31) than did children born to women residing elsewhere in the county (Remy et al., 2017). The authors reported that the risk for intrauterine hypoxia/asphyxia and perinatal jaundice dropped significantly after the factory was closed but that the risk of abnormal birth weight and term remained high. Infants born prior to the factory closure were at a significantly elevated risk for congenital anomalies other than genitourinary anomalies (eye, ear, face, neck, cleft, or chromosomal; RR=1.59, p=0.0489), but the difference in risk was not significant post-closure (RR=0.93).
Among infants born to women living in an e-waste recycling region in China, the cord blood concentrations of chromium were associated with DNA damage of lymphocytes in the cord blood (cell populations of comet r=0.95, p=0.01; cell lengths of tail r=0.89, p=0.00) (Li et al., 2008), and oxidative damage measured by 8-OHdG was associated with Cr (β=0.086 ng/mL, 95% CI 0.014–0.158 ng/mL) (Ni et al., 2014).
ATSDR (2102) reported that there are no studies showing that chromium causes birth defects in humans. In utero exposure to relatively high doses in animals is associated with adverse effects, including decreased numbers of live fetuses/litter, decreased fetal weight, internal and skeletal malformations, and delayed sexual maturation in offspring (ATSDR, 2012).
The Volume 11 committee identified three papers on developmental effects related to Cr6 exposure. One case-control study examined the risk of childhood cancer in California. Using the California Cancer Registry and the California LINE Source Dispersion Model, version 4, to estimate components of air pollution, Heck et al. (2013) reported that prenatal exposure to Cr6 (mean concentration=0.189 ng/m3) was associated with childhood neuroblastoma in children of mothers who lived within 5 km of an air pollution monitor (OR=1.32, 95% CI 1.00–1.74; 75 cases and 14,602 controls who lived within 5 km of an air pollution monitor), but not for those who lived within 2.5 km of one (OR=1.00, 95% CI 0.25–4.00).
As part of the Nurses’ Health Study II, the association between chromium in air pollution and the presence of autism spectrum disorder was examined in 325 cases and 22,101 controls (Roberts et al., 2013). Prenatal exposure to chromium was not significantly associated with autism spectrum disorder for either boys or girls or for both sexes combined among children born between 1987 and 2002, regardless of the quintile of exposure.
McDermott et al. (2015) conducted a systematic review of childhood outcomes associated with in utero exposure to chromium and reported on eight studies, two of which were specific to chromium exposure only (Aschengrau et al., 1993; Li et al., 2008). (Note: Aschengrau et al.  was not included in the ATSDR profile, although the study by Li et al.  of neonates in China was.) The authors reported that one study showed weak associations between chromium exposures and musculoskeletal defects, neuroblastoma, DNA damage, and lymphocyte damage but found no associations with birth weight, gestational age, birth length, autism spectrum disorder, birth defects, or adverse pregnancy outcomes.
Because none of the studies were rated highly for execution and reliability, the authors concluded that there was no association between prenatal chromium exposure and adverse health outcomes in children.
When Aschengrau et al. (1993) compared congenital anomalies in children born to pregnant women (n=1,039) exposed to contaminated community drinking water in Massachusetts with those in children born to 1,177 unexposed women in 1977–1980, they found that congenital anomalies were not significantly associated with chromium levels in drinking water (median concentration=0.5 μg/L) (OR=0.8, 95% CI includes 1).
ATSDR (2012) found that animal data were robust and that they included primate studies as well as multiple studies in rodents, with most of the studies showing adverse effects on sperm morphology and damage to seminiferous tubules and epididymis in male animals, although some results were not supported in a few studies. Species differences between studies, differences in exposure routes—via water versus via food—and differences in maternal toxicity may have contributed to the variation in animal response. Exposed females showed decreased mating and fertility, increased pre- and postimplantation losses, decreased litter size and number of viable fetuses, and increased resorptions. Conflicting results included reduced implantations and numbers of viable fetuses associated with male chromium exposure (ATSDR, 2012).
The ability of Cr6 to cause testicular damage, including its effects on sperm, by oxidative stress has been demonstrated in several animal studies (Hfaiedh et al., 2014; Marouani et al., 2017) and in vitro studies (Das et al., 2015). An additional in vitro study showed that exposing sperm to Cr6 can lead to detrimental developmental effects on subsequent embryos and blastocysts (Yoisungnern et al., 2016). Testicular toxicity has been observed in the form of histopathological lesions and abnormalities in sperm (Marouani et al., 2012).
Studies of in utero exposures in animals have shown a variety of signs of maternal, embryo, and fetal toxicity. Maternal dosing on GD 6–15 had significant effects on the numbers of viable offspring and was associated with morphological abnormalities (Marouani et al., 2011). Female rats exposed in utero showed age-dependent increases in body and ovary weight, delayed estrous cycle, reduced antioxidant enzyme activity, increased levels of lipid peroxidation and hydrogen peroxide concentration in ovaries, and histopathological changes of the ovaries (Samuel et al., 2014). This reproductive and developmental toxicity in female animals was caused by oxidative stress (Stanley et al., 2014).
Some research has suggested that Cr6 exerts epigenetic effects (Schnekenburger et al., 2007): for example, through Cr6 inhibition of benzo[α]pyrene (BaP)-induced gene methylation. Using an in vitro cell model system, Schnekenburger et al. (2007) showed that the transcriptional repression of Cyp1a1 in response to the procarcinogen BaP is influenced by chromium and that this effect is mediated through an epigenetic mechanism. A chromium–HDAC1–DNMT1–chromatin complex is formed that blocks Cyp1a1 histone promoter acetylation and also the recruitment of RNA polymerase II and inhibits aryl hydrocarbon receptor transactivation of Cyp1a1. Blocking this detoxification pathway increases DNA adduct formation. Schnekenburger et al. (2007) proposed that the repercussions would reflect the timing of the developmental exposure and could include a change in imprinting.
Synthesis and Conclusions
Cr6 has been identified as a reproductive and developmental toxicant by ECHA and ATSDR. ATSDR (2012) reported that human studies showed “a significant increase in the number of morphologically
abnormal sperm; significant decreases in sperm count and motility; and greater incidences of complications during pregnancy and childbirth (toxicosis and postnatal hemorrhage),” although these effects were not seen as a result of environmental exposures. The findings in some human epidemiology studies that chromium exposure can lead to increased pregnancy loss and sperm abnormalities in men are supported by a robust animal literature. Animal literature also provides robust support for the effects of Cr6 on semen parameters. Animal studies have exhibited long-term effects on female reproductive organs following in utero and continuous exposure.
Although several studies showed no association between Cr6 exposure and adverse pregnancy outcomes, one study of a community with a plant that used Cr6 showed significant effects of prenatal exposure on both birth weight and duration of gestation (Remy et al. 2017). A strength of this study is that the births were assessed while the plant was in operation and for more than 10 years after the plant had closed. Animal studies also found adverse pregnancy outcomes in rat studies.
On the basis of oral exposure animal studies ATSDR (2012) concluded that Cr6 is a developmental toxicant. In rats and mice, gestational exposure resulted in internal and skeletal malformations and delayed sexual maturation in offspring, although only at relatively high doses (e.g., ≥35mg Cr6/kg/day). Among the studies reviewed by the Volume 11 committee, one study evaluated multiple generations exposed to environmental releases of Cr6, but the exposure was continuous so developmental effects could not be distinguished from transgenerational effects (Roberts et al., 2013). One other study found an association between prenatal chromium exposure, as a component of air pollution, and childhood neuroblastoma (Heck et al. 2013); however, other studies found no association between prenatal Cr6 exposure and birth defects.
None of the available data mimic the potential short-term exposures that veterans often experience.
Epigenetic changes documented in exposed workers are also found in in vitro cell culture studies, but the effects of the epigenetic changes on health are unknown at this time. Cr6 is also recognized as a mutagen (ATSDR, 2012). While teratogenic and epigenetic effects are supported by the data, transgenerational effects have not been clearly established.
The Volume 11 committee concludes that there is sufficient evidence of an association between exposure to Cr6 and reproductive effects in men.
The Volume 11 committee also concludes that there is inadequate/insufficient evidence of an association between exposure to Cr6 and reproductive effects in women.
The Volume 11 committee also concludes that there is limited/suggestive evidence of an association between exposure to Cr6 and adverse pregnancy outcomes.
The Volume 11 committee also concludes that there is sufficient evidence of an association between prenatal exposure to Cr6 and developmental effects.
TABLE 4-5 Summary of Reproductive and Developmental Effects of Hexavalent Chromium
|Reproductive Effects in Men|
|Ali et al. (2011)||Case series of 36 lung tumor samples in chromate workers, 25 tumor samples from unexposed controls. 1975–1997.||Cr6||DNA methylation of APC, hMLH1, and MGMT genes. Increased methylation associated with time worked (p=0.014). Methylation significantly higher in chromate lung cancers versus non-chromate lung cancers (p=0.0001). This study provided no ORs for results.|
|Bollati et al. (2010)||Cohort of 63 workers at an electric-furnace steel plant.||Cr6||miRNA in peripheral blood leukocytes miR-21 and miR-146a not related to Cr6 exposure; miR-222 expression associated with Cr6 (β=0.26, 95% CI 0.0–0.58, p=0.05).|
|Reproductive Effects in Women|
|Remy et al. (2017)||Cross-sectional, ecological. Residents near a factory 1983–2014, Willits, CA.||Residence near factory where Cr6 emissions were high in 1963–1995; rest of Mendocino County served as controls.||Based on hospital discharge data, compared to the rest of the county reproductive organ conditions and neoplasms or pregnancy loss, children of residents had higher rates of respiratory conditions (RR=0.99); perinatal jaundice (RR=1.13); birth defects; low birth weight (RR=1.14); and preterm birth (RR=1.14).|
|Yang et al. (2013)||18 studies of occupational Cr6 poisoning in 14 Chinese cities. 1980–2012. 6,998 workers in China with occupational Cr6 exposures and disease.||Occupational poisoning with Cr6.||Female workers had increased risks of spontaneous abortion (OR=2.31, 95% CI 1.25–4.27) or threatened abortion (OR=20.47, 95% CI 2.60–161.44). Of this group of workers who were pregnant, both spontaneous abortion and threatened abortion were elevated. Minimal ability to ascertain actual Cr6 exposure levels in the plants.|
|Adverse Pregnancy Outcomes|
|Manduca et al. (2014)||Cohort study of babies of parents exposed to weapons in Gaza (48 birth defects, 77 preterm births, 12 healthy babies) in 2011.||Metals in newborn hair samples.||Chromium load in newborn hair not related to birth defects or preterm birth. This study did not provide ORs for results.|
TABLE 4-5 Continued
|Guo et al. (2010)||220 births in Guiyu, China (e-waste recycling region), 119 births from a control area 2008–2009.||Placental concentrations of heavy metals.||Birth length (r=0.002, p=0.977), birth weight (r= –0.029, p=0.675), and gestational age (r=0.002, p=0.971) not related to placental chromium.|
|Li et al. (2008)||200 newborns from Guiyu, an e-waste recycling region, and 102 newborns from Chaonan, 2006–2007.||Cord blood concentrations of chromium.||DNA damage of lymphocytes in cord blood correlated with cord blood chromium (cell populations of comet r=0.95, p=0.01; cell lengths of tail r=0.89, p=0.00). This study did not provide ORs for results.|
|Ni et al. (2014)||201 pregnant women living in e-waste recycling region, Guiyu town, China; and 75 living in Shantou city, 2012–2013.||Cord blood concentrations of heavy metals.||Oxidative damage in neonates measured by 8-OHdG associated with Cr (β=0.086 ng/mL, 95% CI 0.014–0.158 ng/mL).|
|Heck et al. (2013)||Case-control study of 75 cases of neuroblastoma and 14,602 controls from California Cancer Registry, 1990–2007.||Distance of mother’s residence to an air monitor (5 km).||Neuroblastoma associated with Cr6 in air pollution, OR=1.32, 95% CI 1.0–1.74.|
|Roberts et al. (2013)||Nested case-control 325 cases of autism spectrum disorder, 22,101 controls. 1987–2002.||Modeled air pollutants at time and place of birth.||ORs were significant for all metals except for chromium (form unspecified) and arsenic. Autism spectrum disorder not associated with chromium exposure for both sexes in the highest and lowest quintiles.
Highest quintile: OR=1.4; 95% CI 0.9–2.0 Lowest quintile: OR=1.0; no CI provided
NOTE: APC=adenomatous polyposis coli; CI=confidence interval; Cr6=hexavalent chromium; DNA=deoxyribonucleic acid; hMLH1=human mutL homolog 1; MGMT=O6-methylguanine-DNA methyltransferase; miRNA=micro RNA; OR=odds ratio; r=Spearman correlation coefficient; RR=relative risk.
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Abou-Donia, M.B., H.B. Suliman, W.A. Khan, and A.A. Abdel-Rahman. 2003. Testicular germ-cell apoptosis in stressed rats following combined exposure to pyridostigmine bromide, n,n-diethyl m-toluamide (DEET), and permethrin. Journal of Toxicology and Environmental Health Part A 66(1):57–73.
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