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Story at-a-glance:
- Aquaculture promotes itself as a sustainable solution to overfishing, but it actually takes 1.5 to 8 kilograms (3.3 to 17.6 pounds) of wild fish to produce a single kilogram (2.2 pounds) of farmed salmon.
- Fish farms pollute the aquatic environment and spread disease to wild fish. Farmed fish are also an inferior food source, in part by providing fewer healthy nutrients — in part by containing more toxins.
- Research shows farmed salmon contain five times more toxins than any other food tested, including higher levels of PCBs and dioxin.
- Research also warns that farmed Atlantic salmon may contain PBDEs, toxic flame retardant chemicals that have been restricted or banned in the U.S. and many European countries due to their effects on child development.
- Toxins in the fish feed and environmental concentrations of the chemicals have been identified as the two primary culprits.
Fish are an important part of the ecosystem and the human diet. Unfortunately, overfishing has depleted many fish stocks, and the proposed solution — fish farming — is creating far more problems than it solves.
Not only are fish farms polluting the aquatic environment and spreading disease to wild fish, farmed fish are also an inferior food source, in part by providing fewer healthy nutrients, and in part by containing more toxins, which readily accumulate in fat.
Salmon is perhaps the most prominent example of how fish farming has led us astray.
Food testing reveals farmed salmon is one of the most toxic foods in the world, having more in common with junk food than health food. Studies highlighting the seriousness of the problem date back more than a decade and include:
- A global assessment of farmed salmon published in 2004, which found 13 persistent organic pollutants in the flesh of the fish. On average, polychlorinated biphenyl (PCB) concentrations in farmed salmon was eight times higher than in wild salmon, prompting the authors to conclude that “Risk analysis indicates that consumption of farmed Atlantic salmon may pose health risks that detract from the beneficial effects of fish consumption.”
The International Agency for Research on Cancer and the Environmental Protection Agency classify PCBs as probably carcinogenic.
According to the U.S. Centers for Disease Control and Prevention, PCBs elicit a significant number of health conditions in animal studies, including cancer, immunosuppression, neurotoxicity and reproductive and developmental toxicity.
Disturbingly, research suggests contaminated fish is the most common source of PCB exposure, as the chemicals accumulate and build up in the fat tissue.
- A 2005 investigation by another group of scientists concluded even relatively infrequent consumption of farmed salmon may be harmful to your health thanks to the elevated dioxin levels in the fish.
- Toxicology researcher Jerome Ruzzin, who has tested for toxins in a number of different food groups sold in Norway, discovered farmed salmon contain five times more toxins than any other food tested. In light of his own findings, Ruzzin has stopped eating farmed salmon, even though some fishery experts disagree that all farmed salmon is a problem.
- A 2011 study published in PLOS ONE found chronic consumption of farmed salmon caused insulin resistance, glucose intolerance and obesity in mice, thanks to the persistent organic pollutants (POPs) found in the fish.
According to the authors:
“Our data indicate that intake of farmed salmon fillet contributes to several metabolic disorders linked to Type 2 diabetes and obesity, and suggest a role of POPs in these deleterious effects. Overall, these findings may participate to improve nutritional strategies for the prevention and therapy of insulin resistance.”
Researchers: Farmed salmon may contain fire retardants
In 2018, researchers warned that farmed Atlantic salmon sold in the U.S. and UK may also contain polybrominated diphenyl ethers (PBDEs), toxic POPs that have been restricted or banned in the U.S. and many European countries due to their toxic influence on child development. As reported by The Star:
“[A] new study by the University of Pittsburgh has found evidence of PBDEs in food fed to farmed salmon — even in those in supposedly PBDE-free environments.”
PBDEs are a class of chemicals that for years were used as flame retardants, and while restrictions were placed on some of the chemicals in this class in 2004, they can still be found in older products — and in the environment. China, Thailand and Vietnam — three areas that process significant amounts of electronic waste — are known to have higher levels of PBDEs in the environment.
In more recent years, flame retardant pollution has raised serious concern, as these chemicals build up in the environment over time and are in many areas now found in both groundwater and open waters.
Health risks associated with these chemicals, including PBDEs, include infertility, birth defects, neurodevelopmental delays, reduced IQ, hormone disruptions and cancer. In fact, flame retardant chemicals have been identified as one of 17 “high priority” chemical groups that should be avoided to reduce breast cancer.
Toxic fish food blamed for farmed salmon toxicity
You’re probably familiar with the saying that “you are what you eat.” However, a key take-home message here is that “you are what your food eats.”
In other words, whatever the animal you eat consumed, you consume also, which means you really need to know the source of the animals’ feed as well. In the case of farmed fish, toxins in the fish feed and environmental concentrations of the chemicals have been identified as the two primary culprits.
According to the authors, when the fish are raised in areas with high PBDE concentrations in the water, the feed becomes a relatively minor contributor. In PBDE-free waters, on the other hand, elevated concentrations of these toxins in the feed may be high enough to end up on your plate.
As noted by lead author Carla Ng, assistant professor of civil and environmental engineering at the University of Pittsburgh’s Swanson School of Engineering:
“[I]n otherwise clean and well-regulated environments, contaminated feed can be thousands of times more significant than the location of the farm for determining the PBDE content of salmon fillets … The international food trade system is becoming increasingly global in nature and this applies to animal feed as well.
“Fish farming operations may import their feed or feed ingredients from a number of countries, including those without advanced food safety regulations. The United States and much of Europe banned several PBDEs in 2004 because of environmental and public health concerns. PBDEs can act as endocrine disruptors and cause developmental effects. Children are particularly vulnerable.”