LONDON — Researchers seeking evidence of chemical “micropollution” in five rural English rivers have found pesticides in many of the freshwater shrimp they tested. And cocaine in all of them.
The presence of the illegal drug was unexpected because the sites where the researchers gathered their samples, in the eastern coastal county of Suffolk, were miles away from any large city, said the study’s lead author, Thomas Miller, a researcher at King’s College London.
“Although we know that pharmaceuticals, pesticides and so on are in our rivers, most studies in the world don’t look at what’s inside wildlife,” Dr. Miller said in a telephone interview on Friday.
Drugs and other chemicals that are flushed into the sewage system have presented regulators with a puzzle for years. At the low concentrations in which they generally reach waterways, the substances have been found unlikely to affect human health, but their presence is hard to ignore. Recent concerns about plastic waste in rivers and oceans have helped focus attention on the species that live in those waters as victims of pollution.
Last month, researchers working on another project identified a small stream in Belgium so highly polluted that its waters could probably act as a pesticide, The Guardian reported.
In 2016, researchers found a cocktail of drugs, including Prozac, in salmon in Puget Sound, off the coast of Seattle.
The team working on the shrimp study, published online this week in the journal Environment International, said that they had not identified the source of the drugs and that there was little potential for any effect from the low concentrations of cocaine that they had detected.
But some of the compounds they commonly found — which included fenuron, a pesticide no longer authorized for use in Europe — could “be of concern for the environment” or potentially “pose a risk for wildlife,” Dr. Miller said in a statement on Wednesday.
Future studies will examine the chemicals’ effects and give a better idea of the risks, he said, adding that such studies needed to be done more routinely to gain a better picture of the effect of pollution on wildlife.
Some varieties of pharmaceutical pollution have been found to affect behavior in both salmon and shrimp, The Atlantic has reported.
“The impact of ‘invisible’ chemical pollution — such as drugs — on wildlife health needs more focus in the U.K. as policy can often be informed by studies such as these,” Nic Bury of the University of Suffolk, a co-author of the study, said in the statement.
Dr. Miller said that pending further research and policy changes, the public could already act to reduce the presence of drugs in waterways. The best thing, he said, was to return unwanted drugs to pharmacies that offered a takeback program.
Follow Palko Karasz on Twitter: @karaszpalko.