A recent study out of the U.K. found the local freshwater shrimp population has been contaminated with trace amounts of cocaine, other illicit drugs and illegal pesticides.

The study, , tested the chemical exposure of freshwater shrimp and the surface water from 15 locations across Suffolk, a county is southwest U.K., and found trace amounts of cocaine in each sample.

Other illicit drugs, such as ketamine, methamphetamine and MDMA, were also found in some of the samples. The report also indicates a presence of several banned pesticides, most notably fenuron.

The researchers do not have a definitive explanation for the widespread cocaine contamination, but say it could be a result of public use and sewer overflow. The research team believes run-off and leaching from the U.K. agriculture sector is to blame for the pesticides, which they say needs to be investigated further.

It is not determined if these chemicals pose a risk to the shrimp, but a 2013 study from Sweden’s Umea University found that trace amounts of drugs in fish can greatly alter their behaviour, potentially making them an easy meal for predators.

The researchers exposed several wild European perch in an aquarium to extremely diluted levels of anti-anxiety medication and found they were more aggressive and more likely to leave their school than unexposed fish.