A recent US study highlights the high pollution in freshwater fish. The risks are similar in Switzerland, reports RTS.
The US study, published on Science Direct, is focused on levels of per- and polyfluoroalkyl substances, or PFAS. These substances take a very long time to breakdown and persist and accumulate in the environment. The foods with the highest concentrations of PFAS are fish, eggs and fruit, according to the Federal Food Safety and Veterinary Office (FSVO). Exposure to these chemicals is associated with cancer, liver damage, decreased fertility, and increased risk of asthma and thyroid disease, according to the Harvard T.H. Chan School of Public Health. In addition, they can harm the immune system.
The US study analysed data for over 500 composite samples of fish fillets collected across the United States from 2013 to 2015 under the U.S. EPA’s monitoring programs, the National Rivers and Streams Assessment and the Great Lakes Human Health Fish Fillet Tissue Study. The data indicates that an individual’s consumption of freshwater fish can be a significant source of exposure to PFAS.
The median levels of total detected PFAS in freshwater fish across the United States were 278 times higher than levels in commercially relevant fish tested by the U.S. Food and Drug Administration from 2019 to 2022, said the report.
The median fish contamination rate was 9.5 micrograms per kilo. The US Environmental Protection Agency considers water safe to drink at 0.02 micrograms per litre – a litre of water weighs a kilogram. This means a median kilogram of freshwater fish is equivalent to drinking 475 litres of water at the maximum safe level, so a 100 gram portion of freshwater fish would give PFAS exposure equivalent to a month of drinking water at the EPA contamination limit.
PFAS have been used since the 1950s to coat textiles, paper products, and cookware, in some firefighting foams, in the aerospace, photographic imaging, semiconductor, automotive, construction, electronics, and aviation industries. However, environmental contamination began to be documented only in the early 2000s.
Swiss lakes and rivers also contain PFAS, particularly in the canton of Valais where five especially contaminated sites were identified last autumn. The PFAS come mainly from firefighting foams used at industrial sites, for example, the refinery site in Collombey.
These substances are highly mobile and highly persistent, said Yves Degoumois, who is in charge of the polluted sites for Valais’ environmental agency. The site is on the Rhône river plain with a ground water table nearby. Water can move PFAS into the water table. We find these substances in fish at elevated levels with a high accumulation rate, said Yves Degoumois. Concentrations are far higher in fish than in the water, he said. And Valais is not the only Swiss canton with PFAS pollution.