Hair concentration of trace elements and growth in homeless children aged < 6 years: Results from the ENFAMS study

Abstract

BackgroundGrowth is an important indicator of health in early childhood. This is a critical developmental period, during which a number of factors, including exposure to metals, might play a role in later physical and metabolic functions. ObjectiveTo study the association between exposure to arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb) and selenium (Se), and physical growth of children from homeless families aged <6years. MethodsThis study was based on data of the cross-sectional survey (ENFAMS), which was conducted by the Observatoire du Samu Social on a random sample of homeless sheltered families in the Paris region during winter 2013. Families with children under 6years (N=324) were interviewed in 17 languages using face-to-face questionnaires. A nurse took anthropometric measures and collected hair samples where As, Cd, Hg, Pb and Se levels were measured. We calculated weight-for-age Z-score (WAZ), height-for-age Z-score (HAZ) and BMI-for-age Z-score (BMIZ) of children, using the 2006 WHO Child Growth Standards as a reference. Associations between ln-transformed metal exposures and growth outcomes were tested by multivariable linear regression models with adjustment for potential confounders (including maternal anthropometrical and socio-demographical characteristics, gestational age, child birthweight, breastfeeding, food insecurity of the child). Due to missing data (1.6% to 14.2% depending on the variables), we used multiple imputation by chained equations. ResultsA strong positive correlation was found between Pb and Cd levels (r=0.65; p<0.001). Positive associations between Se level and HAZ (β=0.61; p=0.05) and between Cd and BMIZ (β=0.21; p=0.03) and negative associations between As and HAZ (β=−0.18; p=0.05) were no more significant after multiple imputation. A weak negative trend was observed between Cd and HAZ (β=−0.14; p=0.14), while positive trends were found between Se and both WAZ (β=0.55; p=0.10) and HAZ (β=0.51; p=0.06) after multiple imputation. ConclusionOverall, our results found no strong association between exposure to metals and physical growth of homeless children but we observed some trends that were consistent with previous studies. More research is required studying these associations longitudinally, along with higher sample sizes, for better understanding the sources of exposure in homeless population and the potential effects on growth.