Researchers tested popular fish species to measure levels of harmful chemicals called PFAS (forever chemicals) that don’t break down in the environment or our bodies. They found these chemicals in all fish samples tested, with rainbow trout having the highest levels and tilapia having the lowest. The study discovered that different types of fish absorb different forms of these chemicals depending on where they live in the ocean. Understanding which fish contain more of these chemicals and in what forms can help people make informed choices about their diet and help governments set safer food guidelines.

The Quick Take

  • What they studied: How much of a harmful chemical called PFAS (forever chemicals) is found in different types of fish we eat, and whether different fish absorb different forms of these chemicals.
  • Who participated: Multiple species of fish commonly sold in markets, including both bottom-dwelling fish (like cod) and open-water fish (like rainbow trout and tilapia).
  • Key finding: All fish tested contained PFAS chemicals. Rainbow trout had the highest total levels (5.37 nanograms per gram), while tilapia had the lowest (1.29 nanograms per gram). Bottom-dwelling fish contained more types of PFAS variations than open-water fish.
  • What it means for you: If you eat fish regularly, you’re likely consuming small amounts of these forever chemicals. The amounts found are currently considered low, but this research suggests we should monitor fish consumption and choose a variety of fish types rather than eating the same species repeatedly.

The Research Details

Scientists bought different fish species from markets and tested them using advanced laboratory equipment called ion mobility spectrometry. This special equipment can identify not just how much PFAS is present, but also different forms of the same chemical. They tested 13 different PFAS chemicals and found that fish living on the ocean bottom had different patterns of these chemicals compared to fish living in open water. This is the first study to use this advanced technique to identify different forms of PFOA (one type of forever chemical) in fish.

Previous studies could only measure total amounts of these chemicals, but couldn’t tell the difference between different forms. This matters because different forms might behave differently in our bodies and the environment. By identifying which fish contain which forms, scientists can better understand how these chemicals move through the food chain and create more accurate health guidelines.

This study used advanced laboratory technology that is considered state-of-the-art for detecting these chemicals. The research was published in a respected scientific journal focused on food and agriculture. However, the study didn’t specify exactly how many fish samples were tested, which would help readers understand how reliable the results are. The findings are based on market samples, which represents what people actually eat.

What the Results Show

All fish samples contained PFAS chemicals, with PFOA being the most abundant type at an average of 1.21 nanograms per gram. Rainbow trout had the highest total PFAS levels at 5.37 nanograms per gram, while tilapia had the lowest at 1.29 nanograms per gram. The study identified 13 different PFAS chemicals in the fish tested. Linear PFOS (one specific form of a forever chemical) averaged 0.445 nanograms per gram across all samples, with cod showing the highest level at 0.670 nanograms per gram. The advanced testing equipment revealed that bottom-dwelling fish like cod contained more varieties of PFOS forms compared to open-water fish like tilapia. This suggests that where a fish lives in the ocean affects which types of forever chemicals it absorbs.

The research showed that benthic (bottom-dwelling) fish contained linear PFOS and all monosubstituted isomers (different chemical forms), while pelagic (open-water) fish showed linear PFOS and fewer types of these variations. This habitat-specific pattern suggests that the ocean environment where fish live influences which chemical forms they accumulate. The study also successfully identified PFOA isomers in fish for the first time using this advanced technique, opening new possibilities for future research.

This research builds on previous studies showing that PFAS chemicals are widespread in fish and seafood. However, it’s the first to identify and measure different forms of these chemicals separately. Previous studies could only measure total amounts, so this work provides more detailed information about which specific chemical forms are present. The findings align with other research showing that fish from different ocean habitats accumulate different pollutants.

The study didn’t specify the exact number of fish samples tested, making it harder to assess how representative the results are. The research measured current levels in market fish but didn’t track how these levels change over time. The study focused on market samples, so it may not represent all fish species or all geographic regions where fish are caught. The amounts detected are very small (measured in nanograms), and the study didn’t compare these levels to official safety guidelines or assess actual health risks from eating these fish.

The Bottom Line

Based on this research, there’s no need to eliminate fish from your diet, as fish provides important nutrients. However, eating a variety of fish species rather than the same type repeatedly may reduce your exposure to these chemicals. This is a moderate-confidence recommendation based on the chemical patterns found. If you’re concerned about PFAS exposure, limiting consumption of fish species with higher levels (like rainbow trout) and choosing those with lower levels (like tilapia) may help, though the absolute amounts are still considered low.

This research is most relevant for people who eat fish frequently (several times per week), pregnant women and young children (who may be more sensitive to chemical exposure), and people living in areas with known PFAS contamination. People who rarely eat fish don’t need to change their habits based on this study. Policymakers and food safety officials should use this information to develop better guidelines for monitoring PFAS in seafood.

PFAS chemicals accumulate in the body over time, so reducing exposure through dietary changes would take weeks to months to show measurable effects. This isn’t something you’d notice immediately, but consistent choices over time could reduce your total body burden of these chemicals.

Want to Apply This Research?

  • Log the type and frequency of fish consumed weekly, noting whether it’s bottom-dwelling (cod, flounder) or open-water species (tilapia, salmon). Track servings per week to monitor total fish intake.
  • Set a goal to eat 2-3 different fish species per week instead of repeating the same type. Use the app to plan weekly meals with variety: one serving of higher-PFAS fish (like rainbow trout) and two servings of lower-PFAS fish (like tilapia) per week.
  • Track fish consumption patterns monthly to ensure variety. Set reminders to rotate between different fish species. Monitor any changes in fish availability or new research findings about PFAS levels by checking app notifications quarterly.

This research measures PFAS chemicals in fish but does not establish that current consumption levels cause health problems. The amounts detected are very small and below many regulatory limits. This information is for educational purposes and should not replace advice from your doctor or nutritionist. If you have specific health concerns about chemical exposure, consult with a healthcare provider. Fish remains a nutritious food source, and the benefits of eating fish generally outweigh the risks from PFAS at current detected levels. Pregnant women, nursing mothers, and young children should consult their healthcare provider about fish consumption choices.