Lead exposure and indices of height and weight in Uruguayan urban school children, considering co-exposure to cadmium and arsenic, sex, iron status and dairy intake

Abstract

Child growth depends on complex factors including diet, nutritional status, socioeconomic, and sanitary conditions, and exposure to environmental chemicals. Lead exposure is known to impair growth in young children but effects in school-age children are less clear. The effects of co-exposure to low-level lead and other toxic metals on child growth are not well understood. We examined cross-sectional associations of blood lead (BLL) with growth indices (Z scores of body mass index for age, BAZ, and height for age, HAZ) in Uruguayan urban school children (n = 259; ~7 y). Potential differences in these associations in children with lower vs. higher urinary inorganic arsenic metabolites (U-As), urinary cadmium (U-Cd), sex (42% girls), iron deficiency (ID, 39% children), or intake of dairy foods below recommended levels were examined. BLL was measured using AAS, U-As using HPLC-HGICP-MS, and U-Cd using ICP-MS. Dietary information was obtained by two 24-h recalls completed by caregivers. Children's linear growth was within age and sex-appropriate reference values. Overweight (BAZ > 1 2 SD) was found in 20.1%, and obesity (BAZ > 2 SD) in 18.5%, of children. Ranges (5th, 95th percentile) of biomarker concentrations were: BLL, 0.8-7.8 μg/dL; U-Cd, 0.01-0.2 μg/L, and U-As, 4.0-27.3 μg/L. BLL was inversely associated with HAZ ([95% CI]: 0.10 [-0.17, -0.03]) in covariate-adjusted models. Although this association was slightly more pronounced in girls, children without ID, and children with lower U-As, there was little evidence of effect modification due to overlapping CIs in stratified models. BLLs were not associated with BAZ, except for a suggestion of a negative relationship in girls (-0.10 [-0.23, 0.02]) but not boys [0.001 [-0.11, 0.12]). Our findings indicate that exposure to low levels of lead was associated with lower HAZ in apparently normally growing urban school children. Larger future studies should help elucidate if these associations persist over time and across populations.

Keywords: Child; Growth; Metals; School; Urban.