Politicians in the US have gone on the offensive while regulators and industry groups have circled their wagons over a five-month investigation by the Associated Press that has rung alarm bells about trace levels of pharmaceuticals in drinking water.
The widely publicised AP probe found a "vast array" of medicines, including antibiotics, anticonvulsants, mood stabilisers and sex hormones, in the drinking water supplies for at least 41 million Americans in 24 major metropolitan areas.
The news network admitted the concentrations of these drugs in drinking water were "tiny" and far below any therapeutic dose. But scientists are worried about the long-term implications of water contamination for human health, it said.
For example, a number of studies have shown that traces of oestrogen from oral contraceptives or hormone replacement therapies entering water supplies can change the sexual characteristics of animals such as fish or frogs in the wild. The AP also cites recent laboratory research showing that small amounts of drugs can affect human cell processes.
When drug residues find their way into the water supply - mostly through excretion but sometimes also through medicines being dumped or flushed down the toilet - they are not always removed by conventional sewage treatment systems, nor by the filtration processes that convert wastewater to drinking water.
That said, the presence of drug traces in wastewater, surface water (rivers and lakes) or drinking water is by no means a new issue, even if the AP report has brought it very effectively into the wider public eye.
Pharmaceutical companies have been addressing the problem for years through environmental risk testing of their products and other initiatives such as water conservation programmes.
The US industry association, PhRMA, has developed the Pharmaceutical Assessment and Transport Evaluation or PhATE model to facilitate realistic estimates of the concentration and distribution of active pharmaceutical ingredients (APIs) discharged into surface water.
And while the AP warns that the "federal government doesn't require any testing and hasn't set safety limits for drugs in water", it fails to mention the environmental assessments routinely conducted by the US Food and Drug Administration (FDA), as well as by regulatory agencies in other countries, as a condition of market authorisation for pharmaceuticals.
The FDA's requirements do incorporate certain categorical exclusions, such as approval applications that do not involve increased use of the drug's active moiety or, if they do, where the substance's estimated concentration at the point of entry into the aquatic environment would be less then 1 part per billion.
Besides discovering a wide range of drug residues - officials in Philadelphia, for example, said testing in the city had turned up 56 pharmaceuticals or by-products in treated drinking water, including medicines for pain, infection, high cholesterol, asthma, epilepsy, mental illness and heart problems - the AP investigation revealed that only 28 of 62 major US water suppliers contacted tested water for the presence of pharmaceuticals.
Moreover, in the major metropolitan areas where these tests were actually performed, only Albuquerque, Austin and Virginia Beach said tests were negative, the AP reported.
The Environmental Protection Agency (EPA), which has primary responsibility for wastewater in the US, issued a statement claiming the US has "one of the safest drinking water supplies in the world, and EPA is committed to keeping our water clean and healthy".
Nonetheless, the agency is "concerned about the detection of a growing number of pharmaceuticals and other personal care products in water," it added. "These contaminants occur at very low levels in water, and we continue to evaluate their effects on public health and aquatic life."
According to the EPA, it has stepped up its efforts markedly over the last few years to analyse the health effects of contaminants occurring at low levels in water, and determine how best to remove them from wastewater and drinking water.
"We are carrying out national studies and surveys to inform our next steps," the agency stated. "We are reviewing emergent contaminants for regulation, partnering with government agencies and the private sector, and increasing public awareness about product stewardship and pollution prevention."
The EPA also had a message for consumers: "It is important to remember that the toilet is not a trash can, and we encourage safe disposal practices of unused prescription drugs to help keep pharmaceuticals out of the water."
Senators launch probe
Distinctly unimpressed were two US senators: Barbara Boxer, chair of the Senate Committee on Environment and Publics Works, and Frank Lautenberg, chair of the same committee's Transportation Safety, Infrastructure Security and Water Quality Subcommittee.
They plan to hold oversight hearings - probably next month - on the issues raised by the AP's investigation. Meanwhile, Congresswoman Allyson Schwartz has called on the EPA to establish a national taskforce to look into the situation and make recommendations to Congress on any necessary legislative action.
Pharmaceutical companies generally insist that so far research has not shown any appreciable risk to human health from pharmaceutical residues in the water supply, either in the short or the long term. But they do acknowledge the growing concern around the issue, that data on the potential environmental hazards of many older pharmaceuticals are thin on the ground, and that the science informing the debate is still under development.
PhRMA took a similar tack in its response to the AP reports. While recognising that both population growth and increased use of consumer products have meant more chemicals and medicines being discharged into wastewater, it said "great strides have been made to protect water quality by removing impurities using advanced wastewater treatment technologies".
Nonetheless, PhRMA added, "even the best sewage treatment technologies do not completely remove all contaminants". While it was "true that trace levels of pharmaceuticals can be detected in our water supplies, it is important to remember that peer reviewed research studies conducted to date suggest it is highly unlikely that these extremely small quantities of pharmaceuticals would be harmful to human health", the association commented.
Pharmaceuticals approved in the US and Europe are "subject to an extensive regulatory review of the environmental issues pertaining to the manufacture, use and disposal of new drug product", PhRMA pointed out. Moreover, the agency has "longstanding relationships with regulatory and environmental agencies like the FDA, the EPA and the USGS [US Geological Survey], which work together to ensure that the potential impact of pharmaceuticals and the aquatic environment are understood and minimised."
On the scientific front, the industry has developed both the aforementioned PhATE model and the PhACT database, which contains "comprehensive aquatic life data on pharmaceutical compounds" from the peer-reviewed literature.
"Work will continue within and among the pharmaceutical industry, academia, government laboratories and other scientific organisations to further the science and understanding in this area," the association said.
The American Water Works Association (AWWA) noted that water professionals had been researching the occurrence of personal care products and pharmaceutical compounds in drinking water supplies for more than 30 years.
"Today's advanced technology has allowed scientists to detect more substances - at lower levels - than ever before," the AWWA commented.
"To date, however, research throughout the world has not demonstrated an impact on human health from pharmaceuticals in drinking water at the trace levels at which they have been found. People regularly consume or expose themselves to products containing these compounds in much higher concentrations through medicines, food and beverage and other sources."