Manganese and lead levels in settled dust in elementary schools are correlated with biomarkers of exposure in school-aged children.

Abstract

Previously, we showed that manganese (Mn) levels in settled dust in elementary schools increased at a rate of 34.1% per km closer to a ferro-manganese alloy plant in the rainy season. In this study, we investigated how this environmental pollution indicator varied in the dry season and if there was an association with Mn biomarker levels in school-aged children. Dust samples were collected with passive samplers (disposable Petri dishes) placed in interior and exterior environments of 14 elementary schools. Occipital hair, toenails and blood samples were collected from 173 students aged 7-12 years from three of these schools, with varying distance from the industrial plant. Mn and lead (Pb) levels were measured by graphite furnace atomic absorption spectrometry. Mn concentration geometric means (GM) in dust fall accumulation in interior environments of schools located at 2, 4, 6 and>6km-radii from the plant were 2212, 584, 625 and 224μg Mn/m2/30 days, respectively. The modelled rate of change of dust Mn levels decreases by 59.8% for each km further from the plant. Pb levels in settled dust varied between 18 and 81μg/m2/30 days with no association with distance from the plant. Blood lead levels median (range) were 1.2μg/dL (0.2-15.6), of which 97.8% were <5μg/dL. Mn in hair and toenails were 0.66μg/g (0.16-8.79) and 0.86μg/g (0.15-13.30), respectively. Mn loading rates were positively associated with log MnH (β=1.42×10-5, p<0.001) after adjusting for children's age; and also with log MnTn (β=2.31×10-5, p<0.001) independent of age. Mn loading rates explained 18.5% and 28.5% of the variance in MnH and MnTn levels, respectively. School-aged children exposure to Mn, independently of age, increases significantly with school proximity to the ferro-manganese alloy plant.