Female Infertility Associated with Blood Lead and Cadmium Levels Original paper

What was studied?

This original research article investigated the association between blood levels of lead and cadmium (two common environmental heavy metals) and self-reported infertility among women in the United States. The study leveraged data from the 2013–2014 and 2015–2016 cycles of the National Health and Nutrition Examination Survey (NHANES), focusing on reproductive-aged women. The researchers measured blood concentrations of lead and cadmium using inductively coupled plasma mass spectrometry and compared these levels between women who reported infertility (defined as attempting to conceive for at least one year without success) and women who were currently pregnant. Statistical analyses, including logistic regression adjusted for multiple confounders (age, ethnicity, income, education, marital status, smoking, alcohol use, physical activity, BMI), were performed to evaluate whether higher blood metal levels corresponded to increased odds of infertility.

Who was studied?

The study included 124 sexually experienced women aged 20–39 years who participated in the NHANES 2013–2016 cycles and had complete data on blood lead, cadmium, and relevant covariates. Of these, 82 were classified as “infertile” based on self-report, and 42 were “pregnant” at the time of the survey. Women with a history of hysterectomy or bilateral oophorectomy were excluded to ensure reproductive potential. The sample was demographically diverse, but no significant differences were found between infertile and pregnant groups regarding ethnicity, socioeconomic status, education, marital status, health behaviors, or BMI; the infertile group was, however, significantly older.

Most important findings

The study found that even low levels of blood lead and cadmium were associated with significantly increased odds of infertility. After adjusting for confounders, each two-fold increase in blood lead was associated with a 2.6-fold higher odds of infertility, and each two-fold increase in cadmium was associated with a 1.84-fold higher odds. A dose-response relationship was observed for blood lead, with higher tertiles corresponding to higher infertility odds (adjusted ORs for tertiles 2 and 3 vs. tertile 1: 5.40 and 5.62, respectively). Adjusted mean blood lead and cadmium levels were significantly higher in the infertile group compared to the pregnant group. These findings support the hypothesis that environmental exposure to lead and cadmium, even at low levels, may impair female reproductive function. Although the study primarily focused on heavy metal exposure, it is important to note that heavy metals can alter the gut and systemic microbiome, which may further impact reproductive health, though this was not directly assessed in this study.

Key implications

This study provides important evidence that low-level environmental exposure to lead and cadmium is associated with increased infertility risk among US women of reproductive age. These results challenge current safety thresholds for these metals and highlight the need for further population-based research to clarify reproductive toxicity at low exposure levels. Clinicians should consider environmental exposures, including heavy metals, as contributing factors in unexplained female infertility. While not directly examining microbiome profiles, the study’s findings are relevant to a microbiome signatures database, as heavy metal exposures are known to disrupt microbial communities and reproductive hormone regulation, which can influence fertility outcomes.