A few days ago, I came across several articles claiming that farmed salmon is the most toxic food on the planet. So, let’s investigate this matter.

These articles mainly refer to PCBs.

What are PCBs?

PCBs, or polychlorinated biphenyls, are a group of persistent organic pollutants (POPs).

It is estimated that more than 1.3 million tons of pure PCBs were produced between 1930 and 1993 in at least 10 countries, mainly in the USA. However, PCBs were widely exported from producing countries, resulting in their use in at least 114 countries. The roughly 1.3 million tons of pure PCBs, due to dilution for use and subsequent poor management, expanded into 17 million tons of PCB-contaminated materials and waste, with approximately 20–35% of PCBs already released into the environment.

Due to their persistence, bioaccumulative potential, and toxicity, PCBs pose risks to both the environment and human health. They bioaccumulate through the food chain and can reach concerning levels in animals and, consequently, in humans who consume them through the food chain.

Fish consumption is a possible source of PCB exposure, especially when the marine environment has been clearly affected.

Fish become contaminated with PCBs through polluted sediments or by eating contaminated prey. Over time, PCBs accumulate in the fatty tissues of fish and can reach concentrations thousands of times higher than those in water. In the human body, PCBs are easily absorbed and stored in fat tissue. They are excreted slowly and may take many years to be fully eliminated after exposure. They can accumulate in the body over time, stored primarily in fat and the liver. They can also enter infants’ bodies through breastfeeding.

What are the potential health effects for people who consume PCBs?

• They may cause neurodevelopmental issues in developing children.
• At higher concentrations, short-term changes in liver activity may occur without obvious symptoms.
• Animal studies also show that PCBs can affect the immune, endocrine, and reproductive systems.
• PCBs have been classified by the International Agency for Research on Cancer (IARC) as “Possibly carcinogenic to humans” (Group 2A). Group 2A means that there is strong evidence they may cause cancer in humans, but it is not yet conclusive.

Fortunately, their presence in food and animal feed has decreased in recent years thanks to legislative measures and restrictive strategies from public authorities and industry. However, due to their long half-life and environmental persistence, they remain abundant in nature, and seafood—especially fatty fish—continues to be a significant dietary source of them.

Wild vs. Farmed Salmon

Two scientific articles from 2017 and 2020 (listed at the end) agree that farmed salmon, due to its now highly regulated diet and new legislation, contains lower levels of PCBs than wild salmon. However, both wild and farmed salmon have PCB levels within acceptable safety limits. If we look back at studies from 2000, 2006, and other older research, we’ll see that the data were quite different back then.

Fatty fish like salmon are rich in beneficial nutrients such as omega-3 fatty acids. Therefore, the physical and mental health benefits may outweigh the potential risks of consuming low levels of PCBs.

The 2020 study reports that concentrations of dioxins, PCBs, mercury, and arsenic were three times higher in wild salmon compared to farmed salmon—but all levels remained well below the European Union’s safety limits.

The key takeaway is that both farmed and wild salmon continue to be valuable sources of omega-3 fats, vitamins, and minerals, and the benefits clearly outweigh the risks in all cases. It’s a good idea to include fatty fish in your diet at least once a week, and to be mindful of the accuracy of the information we come across.

If you’re interested, you can explore the sources listed below for further study!

References:

• Jensen IJ, Eilertsen KE, Otnæs CHA, Mæhre HK, Elvevoll EO. An Update on the Content of Fatty Acids, Dioxins, PCBs and Heavy Metals in Farmed, Escaped and Wild Atlantic Salmon (Salmo salar L.) in Norway. Foods. 2020 Dec 19;9(12):1901. doi: 10.3390/foods9121901. PMID: 33352671; PMCID: PMC7766777.
• Saktrakulkla P, Lan T, Hua J, Marek RF, Thorne PS, Hornbuckle KC. Polychlorinated Biphenyls in Food. Environ Sci Technol. 2020 Sep 15;54(18):11443-11452. doi: 10.1021/acs.est.0c03632. Epub 2020 Sep 3. PMID: 32816464; PMCID: PMC7759298.
• Melymuk L, Blumenthal J, Sáňka O, Shu-Yin A, Singla V, Šebková K, Pullen Fedinick K, Diamond ML. Persistent Problem: Global Challenges to Managing PCBs. Environ Sci Technol. 2022 Jun 21;56(12):9029-9040. doi: 10.1021/acs.est.2c01204. Epub 2022 Jun 1. PMID: 35647669; PMCID: PMC9228072.
• Getting your omega-3s vs. avoiding those pcbs.-the family HealthGuide (2004) Harvard Health. Available at: https://www.health.harvard.edu/staying-healthy/getting-your-omega-3s-vs-avoiding-those-pcbsthe-family-healthguide (Accessed: 29 June 2023).
• Facts about Illinois’ polychlorinated biphenyls (PCBS) advisory (no date) Illinois Department of Public Health. Available at: https://dph.illinois.gov/topics-services/environmental-health-protection/toxicology/fish-advisories/pcb-facts.html#:~:text=Fish%20become%20contaminated%20with%20PCBs%20from%20living%20near%20contaminated%20sediment,feeding%20fish%20and%20predatory%20fish. (Accessed: 29 June 2023).
• (2022) Oehha.ca.gov. Available at: https://oehha.ca.gov/fish/pcbs-fish-caught-california (Accessed: 29 June 2023).
• Santos, L. L., Miranda, D., Hatje, V., Albergaria-Barbosa, A. C. R., & Leonel, J. (2020). PCBs occurrence in marine bivalves and fish from Todos os Santos Bay, Bahia, Brazil. Marine Pollution Bulletin, 154, 111070. https://doi.org/10.1016/j.marpolbul.2020.111070
• Lundebye AK, Lock EJ, Rasinger JD, Nøstbakken OJ, Hannisdal R, Karlsbakk E, Wennevik V, Madhun AS, Madsen L, Graff IE, Ørnsrud R. Lower levels of Persistent Organic Pollutants, metals and the marine omega 3-fatty acid DHA in farmed compared to wild Atlantic salmon (Salmo salar). Environ Res. 2017 May;155:49-59. doi: 10.1016/j.envres.2017.01.026. Epub 2017 Feb 9. PMID: 28189073.