By Cat Lazaroff
Waterways are contaminated by a medicine chest of antibiotics, hormones, caffeine, painkillers and other drugs, according to a major study of pharmaceutical pollution in US rivers and streams.
The survey -- a baseline for future research -- was performed by the US Geological Survey (USGS). It revealed a list of compounds including the painkillers acetaminophen and ibuprofen, prescription medicines for cardiac disorders and hypertension, and female sex hormones used in birth control pills and hormone replacement therapy.
Although concentrations of most of the compounds were low, typically much less than one part per billion, previous research has shown that exposure to levels even lower than reported in this survey may cause harm to aquatic species. Effects on humans, if any, have not been determined.
The national reconnaissance survey targeted 95 organic wastewater contaminants, and included samples collected at 139 stream sites in 30 states during 1999-2000.
"The 95 chemicals were picked on the basis of estimates about the quantities used, toxicity, potential hormone activity, suspected persistence in the environment and the availability of reference standards and an analytical method," said USGS research hydrologist Dana Kolpin, Ph.D., who headed the national study.
The USGS study suggests that chemicals used in households, agriculture, and industry can enter the environment through a variety of wastewater sources. Those compounds include human and veterinary drugs, including antibiotics, natural and synthetic hormones, detergents, plasticizers, insecticides and fire retardants.
The most frequently detected compounds included:
"Overall, steroids, non-prescription drugs and a chemical found in insect repellents were the chemical groups most frequently detected," Kolpin said. "Detergent metabolites, steroids and plasticizers were generally measured at higher concentrations than the other chemical groups, but concentrations measured in this study generally were very low -- less than one part per billion."
Of the 95 target compounds, the researchers found 82 of them together in at least one stream. In 35 percent of streams tested, the scientists found 10 or more compounds, and in one case, 38 chemicals were present in a single water sample.
"The scientists expected to find most of the compounds, but the prevalence of mixtures was a bit surprising," Dr. Kolpin said. Since this was the first attempt to survey most of these compounds the researchers tried to pick streams most likely to show some contamination. Most are downstream from wastewater treatment plants or intense livestock activity. Only a few are from less developed, more pristine areas.
The reconnaissance study is intended to set a baseline for future research to examine questions such as how far downstream from their sources these chemicals may be found, or how concentrations of these chemicals vary with climate, land use, stream flow rates, or waste characteristics and treatment methods.
When toxicity is taken into account, the measured concentrations of reproductive hormones may have implications for the health of aquatic organisms, according to Dr. Kolpin and his colleagues. However, limited information is available on the potential health effects to human and aquatic ecosystems from low level, long-term exposure or exposure to combinations of these chemicals. For example, the researchers found contamination by 14 antibiotics used in human medicine and animal agriculture.
Some of the antibiotics given to farm animals are excreted in feces or urine, and can reach waterways from leaking waste lagoons or when wastes are spread as fertilizer onto agricultural fields. "The USGS study shows that many antibiotics are moving through our environment in ways that weren't widely appreciated before," noted Dr. Mardi Mellon, senior scientist at the Union of Concerned Scientists.
The study, Pharmaceuticals, hormones, and other organic wastewater contaminants in US streams, 1999-2000, is available at:www.toxics.usgs.gov/regional/emc.html.
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