Description:
Background/Objectives: Exposure to heavy metals has been associated with the development of Neurodevelopmental Disorders (ND's). The plasma zinc/serum copper ratio (Zn/Cu) reflects the health of the metalloprotein system responsible for the detoxification of heavy metals in humans. Low ratios suggest that the metalloprotein system is not efficiently managing these exposures. We sought to explore the relationship between a proxy measure for mercury exposure and clinical ND biomarkers in a sample of children with ND's in Southwestern PA.
Methods: A convenience sample of 185 children with ND's, aged 3-18 with intakes 2005-2008 comprised the study population. Zn/Cu and percent CD4-percent CD8 ratio (CD4/CD8), percent CD8 (%CD8) and percent natural killer cells (%NK) drawn at initial clinical evaluation were used as biomarkers of ND's. The children's intake domicile locations were geo-referenced using ArcView GIS 9.3. Mercury air emissions in pounds per year (2006) from area point sources were procured from the EPA's TRI database. Inverse Distance Weighting (IDW) was used to estimate mercury exposure based on emissions data. Emission rates corresponding to the domiciles of each patient were determined and correlated with study biomarkers.
Results: No interesting correlations were observed for CD4/CD8, %CD8 and %NK and mercury emissions. However Zn/Cu showed a -0.116 Pearson correlation coefficient (p= 0.13) with IDW mercury emissions. Furthermore, scattergram analysis indicates a cluster of children (9) with high (> 200 pounds/year) IDW mercury emissions and low Zn/Cu while there were no children in the same emissions category with Zn/Cu over .73 (Zn/Cu range 0.24- 1.24). A 2 sample t-test revealed a significant difference in Zn/Cu between the high and low exposure groups (p= .02). Environmental Public Health Implications: A subset of children with ND's in Western Pennsylvania may exhaust metalloprotein functioning upon reaching a high threshold of mercury exposure, leading to the dropping of their Zinc/Cu ratios. |