NATURALLY OCCURRING ARSENIC CONTAMINATION OF LOCAL GROUNDWATER RESOURCES IN NORTH CAROLINA, USA, AND A BIOMARKER ASSESSMENT IN EXPOSED POPULATIONS

With approximately 43 million people in the US consuming drinking water from private wells that are exempted from the Safe Water Drinking Act and therefore unregulated, monitoring the water quality of those drinking sources is an important task. In some aquifer systems the levels of naturally occurring arsenic (As) exceed the EPA-Maximum Contaminant Level (MCL), which is a health concern for people consuming water from those wells. While high levels of As exposure may cause acute effects, evaluating the symptoms and diseases directly associated with intermediate levels, but exceeding the Maximum Contaminant Level threshold (10 ppb), are problematic due to the long latency period between chronic exposure and disease occurrence. Understanding the correlation between intermediate levels of As exposure in water and biological changes in the human is difficult but important in order to evaluate the health implications of long-term consumption of As-bearing drinking water

This study is focused in As-rich groundwater from Union County in North Carolina. The study aims to evaluate the distribution of As in the local groundwater and to investigate how different As levels in drinking water from unregulated private wells affect the health of the local population. The data shows that the distribution of As in the groundwater is directly associated with the aquifer lithology, as higher As concentrations are found in wells located in meta-volcanic rocks. The data also show large variations in As concentrations varying from concentrations near zero to 130 ug/L, probably reflecting the heterogeneity of the fracture network of the local aquifer system. In order to understand the population exposure, human keratin in the form of toenails were used as a biomarker of exposure. In total 247 individuals (139 households) were surveyed to assess exposure patterns, basic diet and nutrition information, and quantity of water consumed. Data from well water-nail pairs reveals a statistically significant correlation, in which the male and children sub-populations seem to be most sensitive to As accumulation in the nail. This suggests that this method could be used in assessing the effect of low-level exposure on human population prior to disease occurrence.