Lovers of seafood warned of 'increased risk' of chemicals that cause cancer and other illnesses in new study

People who eat lots of seafood may be increasing their risk of exposure to so-called ‘forever’ chemicals, a new study has warned. Researchers from the University of Dartmouth in the US have found that fish contain previously-underestimated levels of PFAS – harmful, man-made toxins which take thousands of years to break down.

PFAS chemicals, which come from packaging, clothing and even fire-fighting foams, have previously been detected in drinking water – with studies showing that nearly all Americans have measurable amounts in their blood. Too much exposure to PFAS can lead to health issues such as cancer, foetal abnormalities, and liver disorders, meaning high concentrations should be avoided.

So it's bad news for lovers of lobster and shrimp, as these were found to have the highest concentrations of PFAS. But other seafood fans should be wary too, as previous levels of PFAS are thought to have been underestimated.

The study, published in the journal Exposure and Health, appears to question the common consensus that fish-focused diets are nothing but healthy. Previous studies saying seafood regulates inflammation, reduces the risk of heart attacks and helps with weight loss.

The team has stressed that their results do not mean people should stop eating fish. Instead, they have advised public health officials to issue new guidance which outlines how much seafood people can safely consume while still limiting their exposure to PFAS (perfluoroalkyl and polyfluoroalkyl substances).

The team paired an analysis of PFAS concentrations in seafood with a statewide survey of eating habits in New Hampshire, which is one of the top fish consumers in the US. Researchers first measured the levels of 26 varieties of PFAS in samples of the most consumed fish species: cod, haddock, lobster, salmon, scallop, shrimp, and tuna.

They found that shrimp and lobster were the worst offenders, with average concentrations as high as 1.74 and 3.30 nanograms per gram of flesh. This may be due to these species feeding and living on the seafloor, the researchers say, but the reasons remain unclear.

Other seafood concentrations measured generally less than one nanogram per gram of flesh. The team then compared this with how much seafood people in New Hampshire ate to determine how much of a risk was posed – with results showing they aren’t known as fish lovers for nothing.

Men and women in New Hampshire were found to eat just over one and just under one ounce of seafood per day – both of which are more than one-and-a-half times the national average. Around 94 per cent of adults reported that they had consumed seafood in the last month, and more than two-thirds said they had eaten fish within the last week. The most popular types of seafood were salmon, shrimp, and haddock and people who ate fish the most lived on New Hampshire’s coast or near the border with Massachusetts.

Professor Megan Romano, corresponding author, said: “Our recommendation isn't to not eat seafood. Seafood is a great source of lean protein and omega fatty acids, but it also is a potentially underestimated source of PFAS exposure in humans. Therefore, understanding this risk-benefit trade-off for seafood consumption is important for people making decisions about their diet, especially for vulnerable populations such as pregnant people and children.”

Meanwhile, Professor Celia Chan, co-author, highlighted that while guidelines for safe seafood consumption exist for contaminants such as mercury – there are none yet for PFAS.

“Top predator species such as tuna and sharks are known to contain high concentrations of mercury, so we can use that knowledge to limit exposure,” she said. “But it's less clear for PFAS, especially if you start looking at how the different compounds behave in the environment.”

Professor Kathyrn Crawford, the study’s first author, added however that these guidelines would mostly be for the use of those susceptible to pollutants rather than the general population.

She explained: “Most of the population, a.k.a. those who eat a balanced diet with typical, moderate amounts of seafood, should be able to enjoy the health benefits of fish without excessive risk of PFAS exposure.”