Environmental Science & Technology, December 17, 2008

STUDY FINDS TRACE LEVELS OF PHARMACEUTICALS IN U.S. DRINKING WATER

[Rachel's introduction: "...I just don't know what the long-term effects would be on human health from long-term, low-level exposures to complex mixtures of pharmaceuticals and a myriad of other compounds that has been shown to take place."]

A series of news stories by the Associated Press (AP) on pharmaceuticals in drinking water published in the spring of 2008 stirred up a flurry of concern over the quality of tap water in the U.S. The articles detailed the findings of a reporter-led investigation of tests conducted by drinking-water utilities, and they prompted a hearing before the U.S. Senate. Research published in Environmental Science & Technology (DOI 10.1021/es801845a) provides scientific backing to the statement that trace levels of pharmaceuticals are found in drinking water in the U.S., researchers agree.

The paper also is the first to analyze samples taken from the tap water of U.S. homes, says Shane Snyder, R&D project manager at the Southern Nevada Water Authority (SNWA). The 1-year study by Snyder and colleagues at SNWA's Applied R&D Center examines samples from 19 drinking-water treatment facilities across the U.S. The samples were taken from three sources: source water, finished (or treated) water, and distribution water that goes from the drinking-water plant through a series of pipes to private homes and businesses. The team looked for traces of 51 compounds, including 20 pharmaceuticals, and then took the analysis a step farther than the AP investigation by searching for 25 known or suspected endocrine disrupters.

The results show that 34 of the 51 targeted compounds were detected in at least one sample, and the remaining 17 compounds were not found at all. Eleven compounds were found in more than half of the source-water samples; only atrazine, meprobamate, and phenytoin were detected in more than half of the finished-water or distribution-water samples, the paper notes.

"The paper is a nice step forward and provides a very good baseline set of data that will help regulators and other scientists," adds U.S.

Geological Survey (USGS) research hydrologist Dana Kolpin, project chief of the USGS's Emerging Contaminants in the Environment project.

"I think that the study shows that the concentrations are so minute that you really don't have to worry about pharmaceuticals in drinking water, especially when compared with levels of regulated and unregulated disinfection byproducts [DBPs] from finished water using chlorination," says Jorg Drewes of the Advanced Water Technology Center at the Colorado School of Mines.

However, other experts are not ready to concede that these compounds are not harmful. "Current research suggests pharmaceuticals in drinking water are not a huge problem for humans," Kolpin says. "Yet there are a growing number of studies documenting the effects of these compounds on aquatic and terrestrial wildlife," he adds. "I'm not ready to say that these are absolutely of no concern, because I just don't know what the long-term effects would be on human health from long-term, low-level exposures to complex mixtures of pharmaceuticals and a myriad of other compounds that has been shown to take place," Kolpin says.

Other scientists mentioned the unknown effect of adding DBPs to this mixture of drugs, which might actually enhance their toxicity. DBPs are formed when chlorine, a popular disinfectant, is added to drinking water. A recent paper by the U.S. EPA and other researchers indicates significant levels of DBPs in U.S. drinking water. Studies that detect DBPs show they are found at the microgram level, which is 1000 times higher than the concentrations reported in the new ES&T manuscript, adds Drewes.

The high profile attained by the AP series caused some concern among scientists working on this area of research. "Although [the AP series] did report on a topic of emerging interest and concern, it included some errors," says Mike Focazio, a USGS research hydrologist. "At least now people can make more definitive statements about pharmaceuticals in our nation's drinking water that are based on a peer-reviewed scientific study," Kolpin adds.

Trace levels of pharmaceuticals and endocrine-disrupting compounds make their way into tap water from drinking-water plants. This plant pulls water from Lake Mead, which is downstream from a wastewater discharge site, and provides drinking water for Las Vegas.