2003a,b). One study has shown that BLLs do not correlate with the concentration of lead in male reproductive tissues or any somatic tissues examined (Oldereid et al. 1993), but it remains unclear whether BLL or seminal plasma lead concentrations are equally predictive of lead-induced reproductive toxicity in men. Therefore, the committee focused its attention on the use of BLL, commonly assumed to have general applicability as a biomarker of lead exposure.
Female Reproductive Effects
Lead exposure was found to affect female reproductive function in both epidemiologic and toxicologic studies. BLL was associated with changes in hormone concentrations in women; however, study results varied in the magnitude and direction of the changes. The EPA report (2012) states that the selected studies are inconsistent with respect to associations between lead and fertility but suggest that there is evidence of a direct relationship between female lead concentrations and decreased fertility rates. Although the toxicologic and epidemiologic studies examined responsiveness to lead exposure during different exposure periods, both lines of evidence support the conclusion that exposure to lead affects some aspects of reproductive function in women.
The previous EPA (2006) report stated that lead exposure does not result in female sterility but can disrupt female fertility. That finding is supported by animal studies and epidemiologic investigations. Studies by Bloom et al. (2010, 2011) provided evidence that higher BLL was not associated with oocyte fertilization but that embryo cell number was lower in association with higher BLL. Chang et al. (2006) found that women who were seeking care at a fertility clinic had higher BLLs than women who delivered normally at a nearby medical center. In that study, the adjusted effect estimates threshold BLL was 2.5 μg/dL. Al-Saleh et al. (2008a) reported that lower rates of fertilization were associated with BLL but not with follicular lead concentrations. In contrast, Silberstein et al. (2006) found that lead concentrations in the follicular fluid exceeded those in blood and that even at low concentrations the presence of lead in follicular fluid was inversely associated with pregnancy. Those studies are limited in that they each used women who were seeking fertility assistance in an in vitro fertilization clinic where only a woman’s lead levels were considered and thus ignored the potential contribution of lead to sperm dysfunction. The study by Silberstein et al. suffers from a small sample, the fact that follicular and plasma lead concentrations did not correlate well with each other, and potentially confounding factors (such as smoking and occupation) that were not considered in the analysis.
Yin et al. (2008) examined whether there is an association between plasma lead concentrations and anembryonic pregnancies (spontaneous abortion in the first trimester associated with a normal amniotic sac but loss of the embryo). Women who delivered at term had mean plasma lead lower than that of women