Trends in Urinary Lead, Cadmium, Mercury, and Arsenic Exposure among U.S. Women: An Analysis Based on NHANES Data (1999~2020)

Toxic metal pollution in the environment poses a serious threat to human health, and human urine serve as a biomarker reflecting the comprehensive environmental exposure and body burden. Despite the implementation of multiple control measures globally, systematic research on how the exposure levels of sensitive populations (e.g., women) respond to changes in environmental policies is lacking. This population-based cross-sectional study analyzed the urinary data of 10 cycles (1999~2020) from the US National Health and Nutrition Examination Survey (NHANES). We examined temporal trends in urinary concentrations of lead, cadmium, mercury, and arsenic among U.S. females aged 6 years and older using weighted linear regression analyses, in association with sociodemographic factors. Among the 14698 participants included, urinary levels of lead, cadmium, mercury, and arsenic showed significant downward trends, with decreases of 59.7%, 23.1%, 68.1%, and 17.4%. Toxic metal levels were generally higher in adults, being 3.5, 1.8, and 1.4 times higher for cadmium, mercury, and arsenic than in adolescent populations. Urinary lead, cadmium, mercury, and arsenic in overweight individuals were 22.5%, 8.3%, 34.4%, and 21.9% higher than those in obese individuals. Toxic metal exposure levels among U.S. females have declined significantly, indicating the effectiveness of relevant environmental regulatory policies and highlighting the need for targeted interventions in vulnerable populations. This study provides population-based epidemiological evidence for risk assessment of toxic metal exposure, environmental health management, and research on health effects related to ecological damage.