Synthetic chemicals pose growing threat to global water supply | Environment | All topics from climate change to conservation | DW | 14.10.2010

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Synthetic chemicals pose growing threat to global water supply

Synthetic chemicals that damage the human reproductive system are creeping into the world's water supply. Scientists say the chemicals, once waterborne, can quickly spread throughout the globe.

A man gazes at a water sample in a lab

Improperly disposed of medicines dirty water supplies

They're in pesticides and solvents - and even in our medications. An insidious threat to humans and animals, so-called xenobiotics are mostly synthetic chemicals that can interfere with the endocrine system and even act as poisons.

When the chemicals become waterborne they can wreak havoc, especially on the human reproductive system, according to Swedish hydrologist Malin Falkenmark.

"These substances are a serious problem for us and for future generations, because they impact human fertility," Falkenmark said. "In order to tackle this threat, we have to have to track down the source of the pollution. Once a substance is released into water it spreads throughout the world, because there is water everywhere."

Estrogen in the water

A wastewater treatment plant

Xenobiotics can help microorganisms reactivate human waste

Perhaps the best-known example of xenobiotics comes from oral contraceptives. When women take birth-control pills, their bodies pass the synthetic estrogen and progesterone out as waste into the water supply.

University of Basel biologist Patricia Holm said she blames such waterborne xenobiotics for many couples' inability to conceive a child.

"Since these substances work just like hormones, all it takes is a single molecule to cause a reaction in one of the body's receptors," she told Deutsche Welle.

"We can see that sperm counts in many countries have greatly dropped over the past 50 years, sometimes by as much as a half," Holm said. "Among women, we know that breast cancer rates are rising."

Xenobiotics affect animals, too

Two scientists in a lab read from a page

Scientists blame water pollution for infertility - and cancer

Like many human-made problems, xenobiotics don't just affect humans. Scientists have found the substances present in fish, white-tailed sea eagles and even polar bears.

Animal experiments, Holm said, have shown that high levels of estrogen heighten the risk of tumors in rats, just as they raise women's incidence of breast cancer.

Yet researchers' knowledge of xenobiotics and their effects is far from complete. Scientists have only recently discovered that microbes in wastewater treatment plants, which were thought to help break down human waste, can actually reassemble many of the body's waste products. The mixture of synthetic substances in rivers and oceans appears to strengthen this effect.

Holm would like to see the topic of xenobiotics become a matter of public discussion, reaching beyond biologist and chemist circles. She said she wants to see politicians and lawyers, as well as consumers, start asking whether particular medications are necessary, useful, or merely convenient.

Down the toilet

While scientists may be capable of tracking down the source of most harmful pollutants, experts agree that it is better to never release them in the first place. Once a substance reaches water, it will sooner or later make its way back to us, they say - either in our drinking water or through the food chain.

A twisting river

Experts warn that waterborne pollutants can quickly spread across the globe

An estimated third of the medications purchased in Germany are improperly disposed in toilets, directly entering the water supply. Yet it would not be difficult to increase consumers' awareness of the matter, according to Claudia Castell-Exner of Germany's DVGW water conservationists' lobby organization.

"In the 1970s, people were better informed and more aware about medications," said Castell-Exner. "Back then it was clear that you shouldn't flush unused drugs down the toilet."

Until last year, Germany had a system where pharmacies took back leftover medications. According to Castell-Exner, pharmacies stopped that program, claiming they didn't want to take back drugs that were purchased over the Internet.

"That's too bad because patients and consumers are much more open to environmentally friendly practices than we give them credit for," Castell-Exner said.

Author: Agnes Buehring (dl)

Editor: Sean Sinico

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