Maternal smoking during pregnancy and blood lead levels in US children aged 1-15 years: associations modified by age and race.

Objectives: Tobacco smoke is an important source of lead exposure. Maternal smoking during pregnancy likely transfers lead from the mother to the child, contributing to increased lead exposure in developing children. The present study aims to examine the association between maternal smoking during pregnancy and blood lead levels (BLL) in children.

Methods: A total of 18,946 US children aged 1-15 years in the 1999-2016 National Health and Nutrition Examination Survey were included. We defined children with elevated BLL if BLL ≥ 3.5 µg/dL. We estimated odds ratios (ORs) of elevated BLL in children born to mothers who smoked versus nonsmoking mothers.

Results: A decreasing trend in the prevalence of elevated BLL occurred between 1999 and 2016. After adjustment for the trend and other covariates, children whose mothers smoked during pregnancy had significantly increased odds of having elevated BLL (OR = 1.60; 95% confidence interval [CI] 1.25-2.06) compared to children of nonsmoking mothers. The stratified analyses revealed a significant association existed in children aged 1-5 years (OR = 1.88 [95% CI 1.32-2.68]) and aged 6-10 years (OR = 1.79 [1.07-2.98]), but not in youths (11-15 years, OR = 0.72 [0.37-1.40]). Being born to smoking mothers was found to be associated with high odds of elevated BLL in White (1.93 [1.35-2.77]) and Black children (2.03 [1.43-2.87]), but with low odds in Hispanic children (0.46 [0.23-0.92]).

Conclusions: The study demonstrates age- and race-specific associations between maternal smoking during pregnancy and BLL among US children. Maternal smoking contributes to lead exposure in early life. Culturally appropriate interventions are needed to further reduce BLL in the pediatric population.