An environmental action group urged the European Union on Tuesday to boost testing on chemicals and halt pollution in the Baltic Sea because the fish there are so toxic.

The World Wildlife Fund (WWF) said chemical pollution in the Baltic Sea from the late 1980s to the early 1990s caused fish to absorb high amounts of toxic chemicals, known as polychlorobiphenyls or PCBs, which can cause cancer.

WWF said pollution in the Baltic Sea, a largely static sea in northern Europe where the water only changes once every 25-30 years, could be reduced by a contested EU proposal to introduce safety checks on more than 30,000 commonly used chemicals.

“Baltic species are thoroughly contaminated with chemicals,” WWF Senior Policy Officer Ninja Reineke said in a statement. “This is not just a burden of the past but a major on-going problem.”

But the EU chemical industry says the extra testing requirements in the Registration, Evaluation and Authorization of Chemicals proposal will hamper growth and competitiveness while green groups urge tighter controls to protect the environment.

EU states Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland and Sweden all share a Baltic Sea coastline, along with Russia.

Sweden has already recommended that women of childbearing age restrict their consumption of Baltic herring and salmon due to high levels of chemicals in the fish that may harm fertility.