Association between complex exposure to cadmium and mercury and atopic dermatitis in elementary school students: analysis using data from the Korean National Environmental Health Survey (KoNEHS) Cycle 4.

Objectives: Atopic dermatitis (AD) is a common allergic disease with potential links to environmental pollutants, including heavy metals. This study investigates the association between co-exposure to cadmium and mercury and AD among Korean children.

Methods: Data from the fourth cycle of the Korean National Environmental Health Survey (KoNEHS) included 736 elementary school students. Urinary cadmium and mercury levels were measured, and their association with lifetime prevalence of AD was analysed using logistic regression, weighted quantile sum (WQS) regression, quantile g-computation (QGC), and Bayesian kernel machine regression (BKMR). Confounders adjusted included age, sex, urinary cotinine, income, and body mass index. Sensitivity analyses used symptomatic AD and AD treatment as outcome variables.

Results: Among two metals, only cadmium in the highest tertile showed an odds ratio (OR) of 2.39 (95% CI: 1.12-5.10) compared with lowest tertile, with a significant trend per tertile increase (OR 1.58, 95% CI: 1.08-2.31) in multiple logistic regression. Co-exposure analysis using WQS and QGC revealed significant associations with AD prevalence, with WQS showing an OR of 1.47 (95% CI: 1.18-1.83) and QGC showing an OR of 1.60 (95% CI: 1.20-2.13) per tertile increase of exposure. BKMR indicated a dose-dependent relationship between overall exposure and AD risk. For symptomatic AD, similar trend was found. The treatment status of AD did not show a significant association with either heavy metal.

Conclusion: This study suggests a significant association between co-exposure to cadmium and mercury and atopic dermatitis, emphasizing the need to consider combined environmental exposures in epidemiological studies.