Fry maps arsenic levels across NC
By Brant Hamel
With more than two million people in North Carolina obtaining their drinking water from private wells, it is critical for public health to monitor the quality of the groundwater they consume. A team of researchers led by NIEHS grantee Rebecca Fry, Ph.D., published a study in the January issue of the journal Environment International analyzing levels of arsenic, a known carcinogen, in private well water systems across the state.
Fry and her colleagues found consistently elevated levels of arsenic over a period of 11 years in a number of counties that border the Carolina slate belt, including Stanly and Union counties. “Our results indicate a large number of contaminated wells in North Carolina and suggest that ongoing monitoring of well water contaminants is prudent,” they concluded. “Moreover, these data provide new information of specific areas in North Carolina where targeted well monitoring programs can be used in a cost-effective manner.”
A 2010 Outstanding New Environmental Scientist (ONES) (https://www.niehs.nih.gov/news/newsletter/2010/november/spotlight-ones.cfm) awardee, Fry earned her Ph.D. in biology at Tulane University and completed her postdoctoral work at the Massachusetts Institute of Technology with NIEHS grantee Leona Samson, Ph.D., studying the effects of arsenic in Thailand and identifying novel biomarkers of prenatal arsenic exposure ( see story (https://www.niehs.nih.gov/news/newsletter/2008/january/changes.cfm) ). As an assistant professor at the UNC Gillings School of Global Public Health, Fry has expanded her work to examine how arsenic contamination in Mexico resulted in altered epigenetic changes (DNA methylation) affecting known tumor suppressors ( see story (https://www.niehs.nih.gov/news/newsletter/2011/april/science-fry/index.cfm) ). For her latest study, Fry stayed close to home using novel Geographic Information System mapping techniques and a Bayesian statistical model to analyze data points of arsenic levels determined from N.C. well water samples.
A significant public health concern
Arsenic in water has been linked to cancer, heart disease, and neurological disorders. Consequently, the EPA regulates its level to a maximum of 10 micrograms per liter in public drinking water, but there are no corresponding standards for private well water. Fry’s team examined more than 63,000 well measurements taken over an 11-year period by the N.C. Department of Health and Human Services.
The researchers used a novel geocoding algorithm to greatly increase the number of data points that could be spatially located, giving her map a level of detail that has not previously been achieved. They then applied a Bayesian Maximum Entropy framework to predict arsenic levels in areas where data points had not been collected. Fry noted that the methodologies developed for this study are general in nature and could be applied to examine other contaminants in future studies.
On average, only about two percent of the samples were above the U.S. Environmental Protection Agency (EPA) standard, but certain areas had more severe contamination. Almost 20 percent of the wells in Stanly and Union counties were above the EPA standard and one sample reached an arsenic level of 806 micrograms per liter, or 80 times the maximum level set by the EPA.
According to the researchers, it is thought that much of the arsenic contamination found in the study is naturally occurring, due to the underlying geology of the Carolina slate belt and known arsenic deposits. However, there were also a number of counties with elevated arsenic levels that do not border the Carolina slate belt, and additional studies will be needed to determine the source of the contamination.
Arsenic contamination is difficult to mitigate, as there are few simple and cost-effective technologies to deal with the contamination. Modification of well depth may decrease contamination or, if feasible, households can use an alternative water source to limit exposure.
Because an estimated 75,000 people, most with no access to public water systems, use well water in the two counties with the highest levels of arsenic contamination, the team concluded, increasing well-monitoring programs, expanding community education, and biomonitoring of at-risk populations, such as pregnant women, should be future steps in these areas.
Citation: Sanders AP, Messier KP, Shehee M, Rudo K, Serre ML, Fry RC. 2012. Arsenic in North Carolina: public health implications. Environ Int 38(1):10-16.
(Brant Hamel, Ph.D., is a postdoctoral fellow in the NIEHS Molecular Endocrinology Group.)