Issue Date: October 4, 2004
AFTER CHEMICALS GO DOWN THE DRAIN
Tests conducted at a large drinking water treatment plant indicate that some household chemicals widely found in trace amounts in U.S. bodies of water can enter U.S. drinking water.
The results, reported in August by the U.S. Geological Survey (USGS), weren't unexpected. Other studies, mostly in Europe, have made similar findings. Figuring out which of those chemicals ought to be removed and how to remove them are extraordinarily complex tasks, scientists agree.
For almost five years, USGS has monitored U.S. surface water and groundwater--and with this most recent study, drinking water--for some of the most widely used pharmaceuticals, fragrances, hormones, plasticizers, flame retardants, and detergents. (For a list of some contaminants, see table.) The agency has found that what we buy at the drugstore and then wash off or flush down the toilet ends up in U.S. bodies of water, although some at barely detectable concentrations (C&EN, Dec. 3, 2001, page 31).
SURVIVORSSome household chemicals made it through a drinking water treatment plant
|COMPOUND||USE OR SOURCE|
|Tri(dichlorisopropyl) phosphate||Flame retardant|
|Tributyl phosphate||Flame retardant|
|NOTE: U.S. Geological Survey analyzed the untreated and treated water at a large drinking water treatment plant. Of 106 compounds targeted, 40 were detected in the untreated water, and 18 were found in the outgoing water. The water was treated with powdered activated carbon, H2SO4, a coagulant, sodium hypochlorite, flocculation, sedimentation, and filtration. a Suspected to be hormonally active. b Has a drinking water standard: EPA drinking water equivalent level is 700 µg/L; highest concentration found in study was 21 µg/L. c Has a drinking water standard and health advisory: EPA lifetime health advisory is 100 µg/L; EPA drinking water equivalent level is 500 µg/L; highest concentration found in study was 0.096 µg/L. d Has a drinking water standard and health advisory: EPA lifetime health advisory is 10 µg/L; EPA drinking water equivalent level is 500 µg/L; highest concentration found in study was 0.1 µg/L. AHTN = 7-Acetyl-1,1,3,4,4,6-hexamethyltetrahydronaphthalene. DEET = N,N-Dimethyl-m-toluamide. HHCB = 1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[g]-2-benzopyran.
SOURCE: Science of the Total Environment [329, 99 (2004)]
What to do about this is unclear. In the USGS report [Sci. Total Environ., 329, 99 (2004)], the researchers, led by Paul E. Stackelberg, write: "Federal drinking water standards or lifetime health advisories have not been established for most of these compounds." Some of the compounds, individually or in combination, are thought to contribute to the endocrine-disrupting effects that have been observed in some fish species. An increasingly complex picture has begun to emerge on the behavior of pharmaceuticals and personal care products both in water treatment plants and in the environment.
These issues were the focus of a symposium held in August at the American Chemical Society national meeting in Philadelphia. At the symposium, sponsored by the Division of Environmental Chemistry, researchers discussed the difficulty of tracking some chemicals, which can sorb onto particles, transform, or degrade under various conditions. One water treatment may remove a chemical, but the same process might also create one or more chemically transformed products. Some compounds, despite their low solubility in fat, bioaccumulate in fish. On top of all that, researchers suspect that they may not even have thought to look for many of the most important bioactive pollutants.
The ACS symposium also happened to be the first virtual symposium hosted at an ACS national meeting, says Christian G. Daughton, chief of the Environmental Chemistry Branch at the Environmental Protection Agency's National Exposure Research Laboratory, who helped organize the symposium. The proceedings streamed over the Internet, and speakers and attendees from the U.S., Canada, and Europe participated by means of the Web.
Among the studies presented was one that evaluated the fate of contaminants in an urban wastewater treatment plant in the Tampa Bay, Fla., area. The plant treats the water with nitrification, denitrification, and chlorine disinfection. Audrey D. Levine, associate professor of civil and environmental engineering at the University of South Florida, Tampa, along with George R. Kish and Michael T. Meyer of USGS, tested for 125 compounds in a sewer near a hospital. They detected about 50 micropollutants in the untreated wastewater and 27 compounds in the treated water flowing out of the treatment plant. The chemicals removed included polycyclic aromatic hydrocarbons, pharmaceuticals, and hormones. On the other hand, some detergent additives, pesticides, fragrances, and fire retardants made it through.
It's very difficult, if not impossible, Daughton says, to identify one treatment that will remove every pharmaceutical, fragrance, and hormone that is sent down the drain. "There are thousands of distinct drug entities," he says. "Each one will respond to different treatments differently."
What To Do With Expired Pills
If flushing old medicines down the toilet can be bad for the environment, what should one do with expired pills? Poison control centers historically have suggested flushing because too many little fingers, pets, or even strangers were taking old pills out of the trash. Tossing them into the wastebasket also poses risks to the environment, says Christian G. Daughton, chief of the Environmental Chemistry Branch at the Environmental Protection Agency's National Exposure Research Laboratory. Although it might take a long time, drugs in a landfill can get into bodies of water as well.
In some areas, pharmacies or hazardous waste collection programs will accept expired medications. Legally, however, the Drug Enforcement Administration (DEA) must approve any transfer of certain controlled substances from the patient for which they were prescribed, according to Daughton. "In the final analysis," he says, "the best solution is to create formalized take-back programs."
The state of Maine has passed a bill to create such a program. Patients are to receive prepaid mailers that they can send to a post office box maintained by DEA. DEA will then burn the drugs in certified incinerators.
If the trash is the best option in your area, Daughton suggests taping the bottle securely shut, removing or blacking out any personal information (but not the identity of the contents), enclosing it in a larger container, and depositing it in the trash right before the trash collectors arrive.
TREATING WATER with activated carbon is a commonly used method at both wastewater and drinking water treatment plants. (The drinking water plant that USGS studied uses activated carbon.) It is a nonspecific method for removing organic contaminants and some inorganics because many types of chemicals adsorb to the microcrystallized graphite.
Reverse osmosis is another nonspecific means of treating water. Under pressure, water is forced to flow through a semipermeable membrane from the side with a high concentration of contaminants into a space with a low concentration of contaminants. Under ideal conditions, the membrane keeps out everything larger than the membrane pore size.
Professor of environmental health sciences Irwin (Mel) Suffet at the University of California, Los Angeles; assistant professor of soil science Joel A. Pedersen at the University of Wisconsin, Madison; and their colleagues tested reverse osmosis by comparing three different treatment plants in Southern California that treat sewage water for reuse in irrigation and for recharging groundwater. Conventional sewage treatment removed only five of 19 targeted contaminants, including carbamazepine (an anticonvulsant), caffeine, estrone (a natural estrogen), and gemfibrozil (a drug to lower triglycerides). Treatment with reverse osmosis removed, on average, 15 of 19 contaminants.
"No doubt about it. Reverse osmosis removes a wider spectrum of chemicals than granular activated carbon," Daughton says. Yet reverse osmosis is too expensive for treating sewage, he adds. It is most viable for drinking water. In addition, the quality of the treatment depends on the quality of the membrane and its maintenance.
Such treatment studies are helpful for making rough comparisons of one treatment with another. However, most analyses up to now have shown only a portion of the total picture, Suffet stresses. Those 19 target substances are certainly not the only contaminants. In fact, using gas chromatography and mass spectrometry, he and his coworkers identified 35 additional contaminants.
Suffet believes that the strategy of analyzing only targeted compounds is misleading. There could be many more, and the unknowns may be even more important contaminants than the targeted ones.
Even the 150 to 160 compounds that USGS now routinely monitors could be a small fraction of the total, Daughton says. "What is so important to remember is that the ones that USGS found aren't necessarily the universe of the ones that are there. We're only seeing what we set out to find."
To add to the complexity, researchers are beginning to see that they need to be cautious about saying a contaminant is "removed." Although a compound may not be detected anymore, it could simply have been transformed into a new compound or it may have sorbed to particulates.
An increasing amount of research is being conducted on contaminants that accumulate in biosolids, Daughton says. This issue is important, he says, because biosolids are often spread on crop fields as fertilizer. Plants could then, theoretically, take up the concentrated contaminants.
Other contaminants undergo molecular alterations during water treatment. Chlorination and ozonation are known for their ability to transform contaminants.
Mary Bedner, research chemist at the National Institute of Standards & Technology, studied whether the pharmaceuticals acetaminophen, sulfamethoxazole, diclofenac, and metoprolol are oxidized during chlorination. All four compounds "showed significant transformations," she found. Some of the altered products were more toxic than the original drug. And some of them could be easily reduced back to the original drug.
ONE IMPLICATION of Bedner's findings, Daughton says, is that there can be hidden reservoirs of contaminants. "If you take a sample and analyze it, and you don't see something, it doesn't mean that it isn't going to be there in the future."
In addition, the environment itself is likely to play a role in the transformations of contaminants. Kung-Hui (Bella) Chu, assistant professor of environmental and civil engineering at the University of Tennessee, Knoxville, studied the effectiveness of wastewater treatment plants that discharged into a stream originating from the Great Smoky Mountains. She found more contaminants downstream of the plants in the winter than in the summer. Because the temperature of the shallow stream could get as high as 80 °F in the summer and as low as 30 °F in the winter, Chu suspects that many compounds degrade faster in the summer.
Such subtleties make pharmaceuticals in the environment an extraordinarily complex issue, Daughton says. Add to that the possibility that some chemicals may alter the environment. At the ACS symposium, Chris D. Metcalfe, a professor at Trent University, in Ontario, reported how the triglyceride-lowering drug gemfibrozil bioaccumulates in the blood serum of goldfish. Dana W. Kolpin, a research hydrologist at USGS, thinks that a great deal more data about compound toxicity will come out in the next three years.
Yet toxicities are difficult to establish. "My feeling is that [true toxicities] will always be a little bit unknown," Kolpin says. "You can look at toxicity on an individual-compound basis, but in reality there are many compounds out there simultaneously. We've found as many as 38 compounds in a single water sample."
The cumulative effect is what you are really concerned about, Kolpin continues. And such effects may be hard to see: A subtle tweaking of a protein may show up only after years or maybe even generations of exposure to a certain mixture of pharmaceuticals. The first step--determining what's out there--seems like the easy part, he says. "It's figuring out what the effects are that is going to be very tricky."
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