6

Conclusions

The Occupational Safety and Health Administration (OSHA) lead standard for general industry applies to US military firing ranges and was the main focus of the committee’s effort to determine whether “current exposure standards used at ranges are protective”. In addressing its charge, the committee initially evaluated the firing-range environment and associated occupational lead exposures (Chapter 1). Atmospheric lead concentrations collected by the US Army, US Air Force, and US Navy during the last few years showed that mean air lead concentrations on military firing ranges were often above OSHA’s current permissible exposure limit (PEL) of 50 μg/m3 (8-hour time-weighted average). The committee reviewed the historical development of the current OSHA lead standard (Chapter 2) and the toxicokinetics of lead (Chapter 3) and then considered the adverse health effects of lead with respect to noncancer end points (Chapter 4) and cancer outcomes (Chapter 5).

In this chapter, the committee presents its conclusions as to whether current OSHA exposure standards used on firing ranges are protective. The committee used the following questions to guide the presentation of its conclusions:

•  Are OSHA’s guidelines for blood lead levels (BLLs) adequate to protect Department of Defense (DOD) firing-range personnel?

•  Is the current OSHA PEL adequately protective of DOD firing-range personnel?

•  Is the current OSHA action level for medical surveillance appropriate?

•  Were data gaps identified in answering the questions above? Is research needed to fill those gaps?

The committee’s charge also stated that “information will be evaluated on recurrent lead exposures at such firing ranges, and relevant toxicological and epidemiological information on any carcinogenic and non-carcinogenic effects of exposures to lead will be evaluated. The evaluated information will include reviews by the Environmental Protection Agency [EPA] and the National Toxicology



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6 Conclusions The Occupational Safety and Health Administration (OSHA) lead stan- dard for general industry applies to US military firing ranges and was the main focus of the committee’s effort to determine whether “current exposure stan- dards used at ranges are protective”. In addressing its charge, the committee initially evaluated the firing-range environment and associated occupational lead exposures (Chapter 1). Atmospheric lead concentrations collected by the US Army, US Air Force, and US Navy during the last few years showed that mean air lead concentrations on military firing ranges were often above OSHA’s cur- rent permissible exposure limit (PEL) of 50 µg/m3 (8-hour time-weighted aver- age). The committee reviewed the historical development of the current OSHA lead standard (Chapter 2) and the toxicokinetics of lead (Chapter 3) and then considered the adverse health effects of lead with respect to noncancer end points (Chapter 4) and cancer outcomes (Chapter 5). In this chapter, the committee presents its conclusions as to whether cur- rent OSHA exposure standards used on firing ranges are protective. The com- mittee used the following questions to guide the presentation of its conclusions:  Are OSHA’s guidelines for blood lead levels (BLLs) adequate to pro- tect Department of Defense (DOD) firing-range personnel?  Is the current OSHA PEL adequately protective of DOD firing-range personnel?  Is the current OSHA action level for medical surveillance appropriate?  Were data gaps identified in answering the questions above? Is research needed to fill those gaps? The committee’s charge also stated that “information will be evaluated on recurrent lead exposures at such firing ranges, and relevant toxicological and epidemiological information on any carcinogenic and non-carcinogenic effects of exposures to lead will be evaluated. The evaluated information will include reviews by the Environmental Protection Agency [EPA] and the National Toxi- 164

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Conclusions 165 cology Program [NTP]”. In keeping with its charge, the committee initially evaluated key literature presented in the NTP’s 2012 Monograph on Health Ef- fects of Low-level Lead, the EPA’s 2006 Air Quality Criteria Document [AQCD] for Lead Final Report, the 2012 EPA’s Integrated Science Assessment for Lead (Second External Review Draft), the International Agency for Research on Cancer (IARC) monograph Inorganic and Organic Lead Compounds (IARC 2006), and the 2004 and 2011 editions of the NTP Report on Carcinogens. The committee then considered studies that were not included in those reviews. Dur- ing this step, the committee gave greater weight to other systematic reviews and studies that included meta-analyses. The committee used additional considerations to narrow its work. Health- effects data on BLLs below 40 µg/dL were primarily considered because the current OSHA standard aims to maintain BLLs below that concentration. When- ever possible, the committee based its conclusions on occupational and other studies of relevance to DOD personnel that work at firing ranges. Special con- sideration was given to women who might be pregnant or nursing because of the well-known effects of lead on the developing nervous system. The committee also favored studies that considered potential covariates in their statistical analy- ses; these included tobacco use, alcohol consumption, and coexposure to other metals and chemicals. The committee’s conclusions emphasized outcomes asso- ciated with clinical disease rather than early biologic effects. For example, the committee considered decrements in circulating hemoglobin to be more impor- tant than increases in zinc protoporphyrin. In reaching its conclusions, the com- mittee considered the weight of evidence and relied most heavily on findings of lead-induced adverse health effects that had been replicated in multiple peer- reviewed studies. The committee’s conclusions are based on noncancer end points. Although IARC, NTP, and EPA have identified lead as probably carcinogenic in humans, such findings were based largely on studies of laboratory animals. The available human studies on cancer were insufficient for the committee to draw a conclu- sion about BLLs that might be associated with cancer in humans. ARE OCCUPATIONAL SAFETY AND HEALTH GUIDELINES FOR BLOOD LEAD LEVELS ADEQUATE TO PROTECT DEPARTMENT OF DEFENSE FIRING-RANGE PERSONNEL? The primary purpose of the Occupational Safety and Health Act (29 USC 655 et seq) is to ensure, to the extent possible, safe and healthful working condi- tions for every American worker over his or her working lifetime. OSHA’s lead standard requires that a worker who has a single BLL over 60 µg/dL or three BLLs averaging over 50 µg/dL be removed from performing lead work until his or her BLL is under 40 µg/dL on two occasions. Thus, the current OSHA lead standard recognizes a level of concern for workers who have BLLs of 40-60 µg/dL or higher. The committee therefore focused its attention on whether lead

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166 Potential Health Risks to DOD Firing-Range Personnel exposures that result in BLLs of 40 µg/dL or below could result in material im- pairment of health or functional capacity in DOD firing-range workers. It is im- portant to note that BLL generally reflects short-latency, acute health effects of recent lead exposure. However, to some extent, BLLs later in life reflect cumu- lative lead exposure, so the interpretation of studies of BLLs later in life is prob- lematic with regard to defining a “threshold level” for a health effect. The com- mittee also recognized that peak BLLs, average BLLs, and current BLLs could be expected to have different associations with health outcomes, depending on mechanism of action, latency, and other considerations. The committee concludes that the current OSHA standard of a BLL of un- der 40 µg/dL is not sufficiently protective of personnel who have repeated lead exposures on firing ranges. The committee concludes that the evidence is suffi- cient to infer causal relationships between BLLs under 40 µg/dL and impaired neurologic, hematopoietic, renal, reproductive, and cardiovascular function. Ex- amples of acute and chronic adverse health effects that have been reported in the literature and are relevant for DOD firing-range personnel (and their associated mean BLL, benchmark dose, or lowest observed BLLs) are1  Reduced fetal growth and low birth weight (maternal BLL under 5 µg/dL).  Increased cardiovascular-disease mortality (BLL 8 µg/dL or higher).  Increased serum creatinine, an indicator of renal injury (BLL 8-12 µg/dL).  Hearing loss (BLL under 10 µg/dL).  Increased blood pressure (BLL under 10 µg/dL).  Preterm birth (BLL under 10 µg/dL; evidence on this level is growing stronger).  Altered postnatal development and growth (maternal BLL under 10 µg/dL).  Impaired balance (BLL = 14 µg/dL, identified as a benchmark dose).  Neuronal loss and myelin alterations (BLL = 16.9 µg/dL).  Slowed visual evoked potentials (BLL = 17-20 µg/dL).  Decreased psychomotor speed and dexterity and executive function (BLL = 18 µg/dL).  Decreased erythrocyte, hematocrit, and hemoglobin concentrations (BLL = 20-30 µg/dL).  Decreased creatinine clearance and glomerular filtration rate, indicators of renal injury (BLL = 20-30 µg/dL).  Altered parasympathetic and sympathetic activity (BLL = 20 µg/dL or higher).  Slowed brainstem auditory evoked potentials (BLL = 26-30 µg/dL). 1 The reader is referred to Chapter 4 for additional details about individual studies.

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Conclusions 167  Altered verbal memory and learning and reaction time (BLL = 26-30 µg/dL).  Changes in electric activity of the brain evidenced by slow alpha rhythm (BLL = 29 µg/dL).  Altered peripheral sensory nerve function (BLL = 30 µg/dL).  Increased plasma renin activity, angiotensin, angiotensin-converting enzyme, and aldosterone (BLLs = 30-40 µg/dL; these changes are indicative of alterations in renal endocrine functioning and may be responsible, in part, for the increases in blood pressure observed with high BLLs). The committee also considered studies that reported an association be- tween cumulative lead dose, as assessed by cumulative blood lead index (CBLI) or bone lead concentration, and adverse health outcomes. Associations of health outcomes with CBLI or tibia lead concentrations are probably representative of longer-latency, chronic health effects of cumulative dose. In considering CBLI and bone lead data, the committee used the following assumptions: a BLL of 40 µg/dL over a 40-y working lifetime would be equivalent to a CBLI of 1,600 µg- years/dL, and this CBLI is roughly equivalent to a bone lead concentration of 40-80 µg/g (on the basis of the published relation that tibia lead can be estimated as 2.5-5% of the CBLI) (Hu et al. 2007; Healey et al. 2008). Thus, the commit- tee examined evidence that suggested whether a CBLI of under 1,600 µg- years/dL or a bone lead concentration of under 40-80 µg/g may be associated with adverse health effects of lead exposure. Because the current OSHA standard does not address CBLI or bone lead concentrations directly, the committee considered data on this measurement to be supportive evidence for its conclusions. Such data included the following:  Neuronal loss and myelin alterations of brain measured with magnetic resonance spectroscopy (mean bone lead = 7 µg/g).  Hypertension (bone lead concentrations of 13-38 µg/g).  Slow alpha activity on electroencephalogram (mean bone lead = 26 µg/g, mean CBLI = 546 µg-years/dL).  Increased cardiovascular mortality (bone lead concentration over 35 µg/g).  Increased incidence of ischemic heart disease (bone lead concentrations over 35 µg/g).  Decreased hemoglobin and hematocrit (bone lead concentration around 35 µg/g, the difference between the highest and lowest quintiles of bone lead).  Depression symptoms (mean bone lead = 37 µg/g).  Altered quantitative sensory function in peripheral nerves (mean bone lead = 37 µg/g, mean CBLI = 546 µg-years/dL).  Altered psychomotor speed and dexterity (mean bone lead = 38 µg/g).  Slowed brainstem auditory evoked potentials (mean CBLI = 723-934 µg-years/dL).

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168 Potential Health Risks to DOD Firing-Range Personnel  Altered psychomotor speed, dexterity, verbal memory, and executive function (mean CBLI = 765 µg-years/dL).  White matter change in the brain measured by magnetic resonance im- aging (mean bone lead = 39 µg/g, mean CLBI = 826 µg-years/dL). IS THE CURRENT OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION PERMISSIBLE EXPOSURE LIMIT ADEQUATELY PROTECTIVE OF DEPARTMENT OF DEFENSE FIRING-RANGE PERSONNEL? The ability to predict BLLs on the basis of air lead concentrations is cen- tral to the development of the OSHA standard’s PEL. The OSHA PEL of 50 µg/m3 was set to result in the average lead worker’s having a BLL under 40 µg/dL. That BLL was judged by the committee to be inadequate for protecting personnel who had repeated lead exposures on firing ranges (see response to the first question above); thus, the OSHA PEL for lead would also be insufficiently protective. The committee was not able to estimate an air lead concentration that would protect firing-range workers from adverse health effects that could occur at BLLs of 40 µg/dL or lower, but a concentration below the current PEL of 50 µg/m3 clearly is warranted. As discussed in Chapter 3, the OSHA PEL was based on a model produced by the Massachusetts Institute of Technology Center for Policy Alternatives (CPA) (Ashford et al. 1977). The CPA model relied on data from manufacturing operations that may not be directly relevant to firing- range exposures, including differences in lead aerosol particle size, frequency and duration of exposure, assumptions regarding lung deposition and absorption of inhaled particles, and contributions from routes of exposure other than inhalation. IS THE CURRENT OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION ACTION LEVEL FOR MEDICAL SURVEILLANCE APPROPRIATE? The OSHA lead standard also creates an air action level for medical sur- veillance. If it is determined that airborne lead concentrations exceed the action level for more than 30 days/year, an employer must provide a medical surveil- lance program that consists of biologic monitoring and medical examinations and consultations. The OSHA action level for airborne lead exposure is 30 µg/m3 (8-hour time-weighted average). On the basis of the CPA model (Ashford et al. 1977), that exposure concentration would mean that the average lead worker with 1 year of work experience would have a BLL of about 30 µg/dL. Workers with longer job duration would have higher BLLs. As noted above in response to the first question, BLLs under 30 µg/dL have been linked to renal, neurologic, hematologic, reproductive, cardiovascular, and developmental ef-

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Conclusions 169 fects. Thus, the action level for lead would have to be lowered in conjunction with the PEL if the lower PEL is still deemed insufficient to protect all workers. In setting the action level, consideration should also be given to the contribution of oral (hand-to-mouth) exposure to lead. WERE DATA GAPS IDENTIFIED IN ANSWERING THE QUESTIONS ABOVE? IS RESEARCH NEEDED TO FILL THOSE GAPS? The committee did not identify any data gaps that threatened its confi- dence in answering the questions above. However, several data gaps on related subjects were identified during the committee’s deliberations, including the fol- lowing:  Epidemiology studies of firing-range personnel are few.  To the committee’s knowledge, size distribution and chemical speci- ation of airborne lead particles associated with firing ranges have not been per- formed. Such information could be used to estimate the bioavailability of the lead particles found in firing-range air.  The CPA model used in the OSHA standard to predict BLLs from air lead concentrations may not be appropriate for direct application to firing-range personnel, so physiologically based pharmacokinetic or other dosimetry models may need to be developed for this purpose. Those models could consider other biometrics of exposure, such as bone and semen lead levels.  The extent to which occupational oral exposure to lead-based dusts found in the firing-range environment by hand-to-mouth contact contributes to total lead body burden has not been adequately characterized.  The immunotoxicity of low-level lead exposure has been incompletely studied in adults.  Interactions between noise and lead exposure have been incompletely evaluated. POTENTIAL RISK-ASSESSMENT OPTIONS Many groups have proposed alternative management guidelines for BLLs. Most recently, an expert group recommended that BLLs be kept below 20 μg/dL to prevent the acute effects of recent doses (Schwartz and Hu 2007), and this has been supported by the American College of Occupational and Environmental Medicine (ACOEM 2010). For the prevention of the chronic health effects of cumulative doses, the group recommended that tibia lead levels not be allowed to exceed 15 μg/g; this could be achieved, for example, by keeping the average BLL below 10 μg/dL for 40 y (Hu et al. 2007; Schwartz and Hu 2007). Professional organizations—such as ACOEM, the Association of Occupa- tional and Environmental Clinics (AOEC), and the Council of State and Territo- rial Epidemiologists (CSTE)—have called for more protective guidelines. For

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170 Potential Health Risks to DOD Firing-Range Personnel example, ACOEM (2010) has recommended medical removal of workers who have BLLs of 20 µg/dL or higher. AOEC (2007) has recommended more strin- gent guidelines for medical management of lead-exposed workers, which have been incorporated into DOD’s guidance for occupational medical examinations and surveillance (DOD 2007). CSTE (2009) has recommended that the case definition of elevated BLLs in adults be changed from 25 µg/dL to 10 µg/dL. All those organizations recommend that BLLs be kept under 5 µg/dL in preg- nant women to reduce the risk of spontaneous abortion. The US Centers for Disease Control and Prevention (CDC) has developed guidelines that recommend followup activities and interventions beginning at a BLL of 5 µg/dL in pregnant women (CDC 2010) and children (CDC 2012). That BLL is not a “level of concern” or an allowable exposure but rather a level at which it may be prudent to initiate testing and interventions to reduce lead exposure. CDC found convincing evidence that prenatal lead exposure impairs children’s neurodevelopment and so places them at increased risk for develop- mental delay, reduced IQ, and behavioral problems (CDC 2010). The committee agrees that there is a need for additional protection of women of childbearing age, especially pregnant and lactating women. ADDITIONAL CONSIDERATIONS It was unclear to the committee what the potential health risks to DOD fir- ing-range personnel might be, because BLL data specifically on DOD firing- range workers were limited. However, data on airborne concentrations of lead on DOD firing ranges indicate that the current OSHA PEL is exceeded in the performance of some job duties—in some cases by several orders of magnitude. Thus, DOD should consider analyzing BLLs of a representative sample of fir- ing-range workers in all the services and comparing them with BLLs linked to adverse health outcomes so that it can understand potential risks and guide risk- management decisions regarding its ranges. Consideration should be given to risk analyses of available control options to determine how to minimize expo- sure to lead. Control options that could be explored in such analyses include the following:  Ammunition substitution. Exposure of shooters to airborne lead might be reduced by replacing traditional lead bullets with nylon-clad, copper- jacketed, zinc-based, or other forms of ammunition. However, the committee recognizes that training requirements may limit the use of those forms of ammu- nition and that the use of jacketed and other alternative bullets may entail in- creased cost.  Continuing improvement in range design and ventilation. The commit- tee recognizes that some modifications may be difficult to implement, particu- larly as “retrofits” of existing ranges, and that high-efficiency ventilation is ex- pensive to install and operate.

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Conclusions 171  Range cleaning. Scott et al. (2012) found that although ventilation is important for controlling lead exposures, housekeeping can also have a substan- tial effect on lead contamination on surfaces on and around a shooting range. Even on ranges that have good ventilation and that use ammunition with lead- free primers, poor housekeeping or failing to decontaminate a range thoroughly before switching primers may adversely affect lead exposures. The Navy Environmental Health Center notes, in its Indoor Firing Ranges Industrial Hygiene Technical Guide (NEHC 2002), that although there are no established limits for surface lead contamination in workplaces, OSHA (1993) has indicated in a compliance instruction for the construction industry (CPL 2- 2.58) that an acceptable lead loading for nonlead work areas should be 200 µg/ft2. Appendix D of the technical guide suggests clearance levels of 200 µg/ft2 for interior floors and horizontal surfaces and 800 µg/ft2 for exterior concrete.  Hygiene practices. Strict adherence to the OSHA lead-standard rec- ommendations for personal hygiene is critical, and additional hygiene practices should also be considered. Sato and Yano (2006) detected lead contamination on the hands of lead-handling workers at a battery-recycling plant even after work- ers had washed their hands or bathed. More recent investigations have demon- strated that washing with soap and water is not effective in removing lead from skin. Esswein et al. (2011) found that hand decontamination, rather than wash- ing, is required to ensure complete removal of lead. A mixture of isostearamido- propyl morpholine lactate and citric acid applied with a textured absorbent mate- rial was almost 100% effective in removing lead from skin. They suggest that the best method for preventing hand-to-mouth exposure to lead may be skin decontamination and a colorimetric method to detect remaining contamination. If DOD’s occupational exposure limit for lead is lowered, surface and skin decontamination is likely to play an even more important role in effective con- trol of employee exposures than in the past. It will be important for updated guidelines to address the importance of decontamination in more detail and with greater precision. When possible, quantitative levels of contamination should be included in the guidelines rather than qualitative statements regarding the impor- tance of housekeeping. REFERENCES ACOEM (American College of Occupational and Environmental Medicine). 2010. Rec- ommendation to OSHA Regarding Blood Lead Levels. Blood Lead Task Force Proposal to the ACOEM Board of Directors, March 25, 2010 {online]. Available: http://www.acoem.org/BloodLeadLevels.aspx [accessed June 20, 2012]. AOEC (Association of Occupational and Environmental Clinics). 2007. Medical Man- agement Guidelines for Lead-Exposed Adults, Revised April 24, 2007 [online]. Available: http://www.aoec.org/documents/positions/MMG_FINAL.pdf [accessed Apr. 16, 2012].

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172 Potential Health Risks to DOD Firing-Range Personnel Ashford, N.A., R.D. Gecht, D.B. Hattis, and J.I. Katz. 1977. The Effects of OSHA Medi- cal Removal Protection on Labor Costs of Selected Lead Industries. CPA Report No. CPA-77/11. NTIS PB-278653. Center for Policy Alternatives, Massachusetts Institute of Technology, Cambridge, MA. CDC (Centers for Disease Control and Prevention). 2010. Guidelines for the Identifica- tion and Management of Lead Exposure in Pregnant and Lactating Women. U.S. Department of Health and Human Services, Atlanta, GA. November 2010 [online]. Available: http://www.cdc.gov/nceh/lead/publications/LeadandPregnancy2010.pdf [accessed July 27, 2012]. CDC (Centers for Disease Control and Prevention). 2012. Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention Report of the Advisory Committee on Childhood Lead Poisoning Prevention. http://www.cdc.gov/nceh/ lead/ACCLPP/Final_Document_030712.pdf [accessed October 1, 2012]. CSTE (Council of State and Territorial Epidemiologists). 2009. Public Health Reporting and National Notification for Elevated Blood Lead Levels. Position Statement 09- OH-02, Revised June 10, 2009 [online]. Available: http://www.cste.org/dnn/Ann ualConference/PositionStatements/09PositionStatements/tabid/333/Default.aspx [ac- cessed Apr. 16, 2012]. DoD (U.S. Department of Defense). 2007. Occupational Medical Examinations and Sur- veillance Manual. DoD 6055.05-M. U.S. Department of Defense, Undersecretary of Defense for Acquisition, Technology and Logistics, Washington, DC [online]. Available: http://www.dtic.mil/whs/directives/corres/pdf/605505mp.pdf [accessed Apr. 16, 2012]. Esswein, E.J., M.F. Boeniger, and K. Ashley. 2011. Handwipe method for removing lead from skin. J. ASTM Int. 8(5):1-10. Healey, N., D.R. Chettle, F.E. McNeill, and D.E. Fleming. 2008. Uncertainties in the relationship between tibia lead and cumulative blood lead index. Environ. Health Perspect. 116(3):A109-A110. Hu, H., R. Shih, S. Rothenberg, and B.S. Schwartz. 2007. The epidemiology of lead toxicity in adults: Measuring dose and consideration of other methodologic issues. Environ. Health Perspect. 115(3):455-462. IARC (International Agency for Research on Cancer). 2006. Inorganic and Organic Lead Compounds. IARC Monographs on the Evaluation of Carcinogenic Risks to Hu- mans Vol. 87. Lyon, France: IARC [online]. Available: http://monographs.iarc.fr/ ENG/Monographs/vol87/index.php [accessed Oct. 2, 2012]. NEHC (Navy Environmental Health Center). 2002. Indoor Firing Ranges, Industrial Hy- giene Technical Guide, Technical Manual NEHC-TM6290.99-10 Rev. 1. Navy En- vironmental Health Center, Bureau of Medicine and Surgery. May 2002 [online]. Available: http://www.nmcphc.med.navy.mil/downloads/IH/indoor_firing_range.pdf [accessed Dec. 19, 2011]. OSHA (Occupational Safety and Health Administration). 1993. 29 CFR 1926.62, Lead Exposure in Construction; Interim Final Rule--Inspection and Compliance Proce- dures. OSHA Instruction CPL 2-2.58, December 13, 1993. Occupational Safety and Health Administration, Office of Health Compliance Assistance [online]. Available: http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=1570 &p_table=DIRECTIVESaccessed Nov. 28, 2012]. Sato, M., and E. Yano. 2006. The association between lead contamination on the hand and blood lead concentration: A workplace application of the sodium sulphide (Na2S) test. Sci. Total Environ. 363(1-3):107-113.

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Conclusions 173 Schwartz, B.S., and H. Hu. 2007. Adult lead exposure: Time for change. Environ. Health Perspect. 115(3):451-454. Scott, E.E., N. Pavelchak, and R. DePersis. 2012. Impact of housekeeping on lead expo- sure in indoor law enforcement shooting ranges. J. Occup. Environ. Hygiene 9(3):D45-D51.