Rethinking mercury toxicokinetics: Factors influencing mercury disposition in young children

Background:  Excessive accumulation of different forms of mercury (Hg) is associated with health disorders including developmental neurotoxicity.   Objective:  To explore key factors determining mercury disposition in young children.   Methods: The data were obtained from children aged 2-5 years (n=390), who provided valid measurements of blood and hair Hg in the National Health and Nutrition Examination Survey 1999-2000. As hair is one of the major elimination routes for Hg, the hair-to-blood Hg ratio was used to examine influential factors in the disposition kinetics of Hg for a given level of exposure concentration, as assessed by blood (total) Hg. Covariates including age, gender, race, body mass index percentile (standardized for age) and poverty income ratio (PIR), an indicator of socioeconomic status (SES), were examined in the multiple linear regression analyses. Logarithmic transformations were applied when necessary.   Results: Of the factors examined in the current study, gender was the leading factor followed by BMI and PIR in determining the hair-blood Hg ratio. In general, the hair-blood Hg ratio was approximately 25% lower among young girls aged 2-5 yrs than their male counterparts after covariate adjustment. Interestingly, the hair-to-blood Hg also appeared to be about 15% lower in children with lower PIR than those with higher PIR, suggesting children from poor or low-income families may carry a higher body burden of Hg for a given Hg exposure, since their clearance to hair is lower. The hair-to-blood ratio also tended to lower in children with higher BMI.   Conclusions: While the current study identified several factors that one may need to consider when examining Hg toxicokinetics, it also found a disproportionate exposure burden placed on individuals with lower SES as compared to their counterparts. Further research with a larger sample size and measurement of fecal Hg is warranted to confirm our findings.   

Impact/Purpose

To inform the selection of dose conversion for Hg toxicity assessment, the goal of this study is  to investigate key determinants of the hair-to-blood Hg ratio in children aged 2-5 years using the data from a nationally representative health survey of the U.S. non-institutionalized population, the National Health and Nutrition Examination Survey (NHANES).

Citation

Lin, Yu-Sheng, M. Dzierlenga, P. Schlosser, AND V. Morozov. Rethinking mercury toxicokinetics: Factors influencing mercury disposition in young children. SRA 2021 ANNUAL MEETING, NA, Washington DC, December 05 - 09, 2021.