A comprehensive survey of the drinking water for more than 28 million Americans has detected the widespread but low-level presence of pharmaceuticals and hormonally active chemicals.
Little was known about people's exposure to such compounds from drinking water, so Shane Snyder and colleagues at the Southern Nevada Water Authority in Las Vegas screened tap water from 19 US water utilities for 51 different compounds. The surveys were carried out between 2006 and 2007.
The 11 most frequently detected compounds - all found at extremely low concentrations - were:
• Atenolol, a beta-blocker used to treat cardiovascular disease
• Carbamazepine, a mood-stabilising drug used to treat bipolar disorder, amongst other things
• Estrone, an oestrogen hormone secreted by the ovaries and blamed for causing gender-bending changes in fish
• Gemfibrozil, an anti-cholesterol drug
• Meprobamate, a tranquiliser widely used in psychiatric treatment
• Naproxen, a painkiller and anti-inflammatory linked to increases in asthma incidence
• Phenytoin, an anticonvulsant that has been used to treat epilepsy
• Sulfamethoxazole, an antibiotic used against the Streptococcus bacteria, which is responsible for tonsillitis and other diseases
• TCEP, a reducing agent used in molecular biology
• Trimethoprim, another antibiotic
The concentrations of pharmaceuticals in drinking water were millions of times lower than in a medical dose, and Snyder emphasises that they pose no public health threat. He cautions, though, that "if a person has a unique health condition, or is concerned about particular contaminants in public water systems, I strongly recommend they consult their physician".
Christian Daughton of the EPA's National Exposure Research Laboratory says that neither this nor other recent water assessments give cause for health concern. "But several point to the potential for risk - especially for the fetus and those with severely compromised health."
Daughton says the contamination surveys help people realise how they are intimately and inseparably connected with their environment. "The occurrence of pharmaceuticals in the environment also serves to make us acutely aware of the chemical sea that surrounds us," he says.
While the US government regulates the levels of pathogens in US drinking water, there are no rules for pharmaceuticals and other compounds, apart from one: the herbicide atrazine. The atrazine levels measured by Snyder and colleagues were well within federal limits.
Snyder says water utilities could make drinking water purer. But the costs of "extreme purification" - far beyond what is needed for safety alone - are huge in terms of increased energy usage and carbon footprint. Ultra-pure water might not even be safe, adds Snyder.
The widespread occurrence of pharmaceuticals and endocrine disruptors reflects improved detection techniques, rather than greater pollution, says Snyder. Contamination is a fact of modern life, he adds.
"As we continue to populate and aggregate, our wastes will certainly accumulate where we live," he says. "We as a species have decided to live a modern life, with pharmaceuticals, plastics, transportation - therefore we must accept that there will be a certain degree of contamination."
Journal reference: Environmental Science and Technology, in press