Blood heavy metal levels and bone turnover markers in Korean elementary school children

Although the health effects of heavy metal exposure in children are well documented, their impact on bone metabolism is less understood. Bone turnover markers such as serum C-terminal telopeptide of type I collagen (CTX) and serum Procollagen type I N-terminal propeptide (P1NP) can help assess skeletal effects. This study aimed to evaluate the relationship between blood concentrations of mercury (Hg), lead (Pb), and cadmium (Cd) and bone turnover markers in children.

We conducted a cross-sectional study of 221 elementary school children aged 11-13 years attending four schools around a municipal incinerator, one of which served as a control area. Blood Hg, Pb, and Cd and serum CTX and P1NP were measured. All exposure and outcome variables were natural log-transformed, a choice supported by Box-Cox analysis. A single primary model, including all three metals and adjusted for age, sex, body mass index, and residential area, was specified in advance and fitted with heteroscedasticity-consistent standard errors.

Blood Pb was positively associated with both markers: each 2-fold increase in blood Pb corresponded to an 18.6% higher CTX (95% CI: 7.4-31.0, p < 0.001) and an 18.4% higher P1NP (95% CI: 3.6-35.4, p = 0.014). Both associations persisted after correction for multiple testing and across all sensitivity analyses, including adjustment for proxies of pubertal growth. Hg and Cd were not associated with either marker.

Blood Pb was associated with higher bone turnover in children at concentrations lower than those previously reported for Korean children of similar age, involving both bone resorption and formation. Because the design was cross-sectional and increased bone remodelling may itself mobilise skeletal Pb, the direction of this relationship cannot be determined, and longitudinal research is warranted.