Rise in water contaminants

Neither were they shocked to find prescription drugs ranging from antibiotics to the anti-convulsive carbamazepine. Researchers realised more than 15 years ago that pharmaceuticals — excreted by users, dumped down drains — were slipping through wastewater treatment systems.

But though she is a leading expert in ‘emerging contaminants’, Dr Swackhamer was both surprised and dismayed by the sheer range and variety of what she found. Caffeine drifted through the river water, testament to local consumption of everything from coffee to energy drinks. There were relatively high levels of acetaminophen, the over-the-counter painkiller. Acetaminophen causes liver damage in humans at high doses; no one knows what it does to fish.

“We don’t know what these background levels mean for environmental or public health,” she said.

The number of chemicals contaminating our environment is growing at exponential rate, scientists say. A team of researchers at the US Geological Survey tracks them in American waterways, sediments, landfills and municipal sewage sludge, which is often converted into agricultural fertiliser. They’ve found steroid hormones and the antibacterial agent triclosan in sewage; the antidepressant fluoxetine (Prozac) in fish; and compounds from both birth control pills and detergents in the thin, slimy layer that forms over stones in streams.

“We’re looking at an increasingly diverse array of organic and inorganic chemicals that may have ecosystem health effects,” Edward Furlong, a research chemist with the USGS office in Denver and one of the first scientists to track the spread of pharmaceutical compounds in the nation’s waterways. “Many of them are understudied and unrecognised.”

In an essay last week in the journal Environmental Science & Technology, titled “Re-Emergence of Emerging Contaminants”, editor-in-chief Jerald L Schnoor called attention to both the startling growth of newly registered chemical compounds and our inadequate understanding of older ones.

Dr Schnoor, a professor of civil and environmental engineering at the University of Iowa, also noted rising concern among researchers about the way older compounds are altered in the environment, sometimes taking new and more dangerous forms.

Some research suggests that polychlorinated biphenyls, or PCBs, are broken down by plants into even more toxic metabolites. Equally troubling, scientists are finding that while PCBs are banned, they continue to seep into the environment in unexpected ways, such as from impurities in the caulk of old school buildings.

PCBs have long been identified as hazardous, but not every contaminant is so risky, Dr Schnoor emphasised.

“Out of the millions of chemical compounds that we know about, thousands have been tested and there are very few that show important health effects,” he said in an interview. But, he added, the development of new compounds and the increasing discovery of unexpected contaminants in the environment means that the nation desperately needs a better system for assessing and prioritising chemical exposures.