The nation’s waterways are awash with traces of painkillers, caffeine, antibiotics and other products commonly passed through humans and farm animals, according to a recent study by the U.S. Geological Survey.
Among the 95 substances detected in waterways as part of the study were contraceptives, insect repellents, perfumes and nicotine — substances which generally go untreated at wastewater treatment plants but may pose threats to the aquatic environment.
The USGS found at least one of the compounds in 80 percent of the 139 stream sites sampled nationwide. The sampling sites included a half dozen locations in the Bay watershed.
Generally, the substances were found only at low levels, often at concentrations of less than 1 part per billion. But there is little information about the potential human or aquatic health effects that may result from low-level, long-term exposure to combinations of the chemicals that may be encountered.
“Little is known about the environmental occurrence of many chemicals we use to maintain and improve the quality of our daily lives,” said Robert Hirsch, USGS Associate Director for Water. “This study begins a process of exploring the occurrence of these chemicals in our nation’s streams.”
Although concern has grown about such contaminants in waterways, the USGS study, published in the March 15 issue of the journal Environmental Science & Technology, was the most comprehensive look at the levels of antibiotics, hormones and other organic compounds in the nation’s streams.
Scientists believe the chemicals — sometimes called pharmaceutical and personal care pollutants, or PPCPs — could pose risks not only to aquatic life, but to downstream water users.
Pharmaceuticals and chemical byproducts from animal agriculture are among the emerging chemical contaminant issues singled out in the Bay Program’s Toxics 2000 Strategy for study, and potentially new commitments by the Bay states.
Many such substances fall through the cracks of existing clean water laws. They generally are not defined as pollution — the EPA has no water quality criteria for 81 of the 95 chemicals examined by the USGS.
Further, the Food and Drug Administration does not review pharmaceuticals for potential environmental impacts.
One of the reasons so little is known about the chemicals in the environment is that it has been difficult to track the contaminants at such low levels.
As part of the study, the USGS developed new laboratory methods that allow it to measure the concentrations of 95 wastewater-related chemicals in water samples.
The chemicals were selected because they are expected to easily enter waterways through wastewater discharges or feedlot runoff, are used in large quantities, and may have human or environmental health implications. Still, USGS scientists cautioned, the chemicals “are just a small subset of compounds being used by society.”
The actual samples were collected during 1999 and 2000, from waterways in 30 states. The sites were selected based on their proximity to likely sources of the chemicals.
As a result, the study did not provide information about how far downstream the chemicals may be transported — a subject that USGS scientists said was ripe for further examination.
The most frequently detected compounds included coprostanol (a fecal steroid); N-N-diethyltoluamide (an insect repellent), caffeine, triclosan (antimicrobial disinfectant), tri(2-chloroethyl)phosphate (a fire retardant) and 4-nonylphenol (a detergent metabolite).
Amounts were generally too low to expect acute impacts, the USGS said, but more subtle, chronic effects could result from continued low-level exposure to the chemicals.
In waterways, the study said the chemicals may impair the development of aquatic wildlife, affect reproduction, increase the risk of cancer, lead to the development of antibiotic-resistant bacteria, and increase the potential of toxicity resulting from the chemicals mixing together in the environment.
At least a third or the targeted chemicals are known, or suspected, endocrine disrupters, which can mimic or block endocrine system processes that help to guide development, growth, reproduction, behavior and other bodily functions.
Of particular concern were the antibiotics, which were detected at about half of the study locations. The paper cautioned that “even low-level concentrations in the environment could increase the rate at which pathogenic bacteria develop resistance to these compounds.”
Many streams had multiple contaminants. The median number of chemicals detected was seven. One stream had 38. The fact that so many streams had several contaminants points to the need for future studies to examine the effects of combinations of chemicals that may be encountered by aquatic life, the scientists reported.
Sometimes, though, sorting out the origin of substances could be difficult. Some of the chemicals studied by USGS, including hormones, are naturally produced by plants and animals, so sorting out which are related to pharmaceuticals could be difficult. Studies have suggested that hormones released into the waterways may alter sexual characteristics in fish and other wildlife exposed to the chemicals.
The USGS said its study could help guide future research in such issues.
The study was conducted by the USGS Toxic Substances Hydrology Program. It is available on the internet at: http://toxics.usgs.gov/