Association Between Tobacco Smoke Exposure and Cadmium Biomarkers in the US Population: NHANES 2015–2020

Cigarette smoke contains toxic chemicals, such as cadmium (Cd), which accumulate in the body and cause severe health issues. This study examined associations between tobacco smoke exposure on Cd biomarker levels in the US population. A cross-sectional study was conducted using data from the National Health and Nutrition Examination Survey (2015–2020) for children, adolescents, and adults in the US. The association between serum cotinine levels and blood and creatinine-adjusted urine Cd levels was investigated. Smoke exposure status was categorized by serum cotinine levels into no exposure, light secondhand exposure, heavy secondhand exposure, and active smoking. Survey-weighted multivariable linear regression was conducted to estimate geometric means (GMs) and ratios of GMs, adjusting for covariates. Among adults, compared to individuals with no exposure, those with cotinine concentrations corresponding to the range commonly interpreted as heavy secondhand smoke exposure and active smoking had 1.55 times (95% CI: 1.30, 1.84) and 3.20 times (95% CI: 2.87, 3.57) higher blood Cd levels, respectively, with evidence of a dose-response relationship (p-trend < 0.001). However, for urinary Cd, active smokers showed significantly elevated levels (1.57 times; 95% CI: 1.45, 1.71), while no significant elevation was observed for secondhand smoke exposure. Among children and adolescents, Cd levels did not differ across smoke exposure statuses. Additionally, older age, female sex, lower poverty-income ratio, lower education, and racial minority status were associated with higher Cd exposure. These findings indicate that higher serum cotinine concentrations were associated with higher Cd biomarker levels among adults in the US population.