Disparities in Blood Lead Levels in the United States: The National Health and Nutrition Examination Surveys (NHANES)

Background: Lead, an environmental toxin with no known safe exposure level, is a significant public health concern. Elevated blood lead levels (BLLs) have been linked to adverse health outcomes in children and adults. Previous research has explored BLL variations by race, socioeconomic status, and smoking status using earlier waves of the National Nutrition and Health Examination Survey (NHANES). However, our study uniquely incorporates the role of pesticides and volatile toxicants (i.e., chemicals in household products known to contaminate water sources) and factors known to predict BLLs. By adopting the social determinants of health (SDoH) framework, we aim to comprehensively examine factors associated with BLLs among children and adults.

Methods: Secondary data analysis was conducted with a nationally representative sample of children (6-17) and adults (18+) from the NHANES 2017-2020 (N=15,560). BLLs were measured as micrograms of lead per deciliter of blood (μg/dL) and operationalized as is and dichotomously using a cut-off of μg/dL >= 0.855 [the “typical” BLL in adults (CDC, 2019)] for the adult models. Predictor variables included SDoH factors such as education, pesticide use, volatile toxicant exposure, demographics (age, gender, and race/ethnicity), current tobacco use, and secondhand tobacco exposure. SDoH’s economic stability factor (household food insecurity) and prenatal tobacco exposure were included in the model examining children. All analyses were weighted. Multiple linear regressions (continuous BLL) and logistic regressions (dichotomous BLL) were conducted in Stata/MP v18.

Results: The average BLL was 1.0 μg/dL (SE = .03) for adults and 0.49 μg/dL (SE = .02) for children. The average adult sample was 47.4 years old (SE=.71); 62% identified as White, 12% as Black, and 52% were male. Sixty-one percent had some college education or more. The average child sample was 14.6 years old (SE=.09); 49% identified as White, 15% Mexican American, 15% Black, and 52% were female. Among adults, tobacco use and being older, female, and Black or Asian (vs. White) were significantly associated with higher BLLs (p<0.001), while higher education and being non-Mexican Hispanic were negatively associated with higher BLLs (p<0.05). Among children, being female, Asian (vs. White), and prenatal tobacco exposure were positively associated with higher BLLs (p<0.05), with no significant protective factors in this model. Pesticides and toxicants were not significant predictors for both child and adult models. The adult model with the dichotomous operationalization of BLLs produced equivalent results.

Conclusion and Implications: Persistent racial inequities were present among adults and children. While pesticides and toxicants were not significant predictors of elevated BLLs, these findings justify accelerating policies such as the Lead Pipe and Paint Action Plan to eliminate lead in older low-income homes. Furthermore, women’s BLLs were higher than men's, contradicting findings from studies using earlier waves of NHANES. Gender inequities need further examination. Results also suggest that current tobacco use and prenatal tobacco exposure are salient predictors beyond pesticides and toxicants. Additionally, prenatal tobacco exposure may increase children’s BLLs, highlighting another health detriment of prenatal tobacco use. Future studies are needed to keep investigating the impact of SDoH on BLLs and related inequities.