Salmon's Health Risks: Polluted Waters' Impact

Salmon is a popular food fish, particularly in North America, where the majority of the salmon consumed is farmed. However, the farmed salmon industry has been criticized for its negative impact on the environment and human health. One of the main concerns is the pollution of waterways, which can lead to contaminated salmon flesh. Salmon migrate to the sea, where they pick up contaminants deposited in the ocean by polluted rivers. These contaminants can include pesticides, flame retardants, and heavy metals such as mercury and lead, which can have harmful effects on human health. While the consumption of contaminated salmon has been linked to an increased risk of certain cancers and other illnesses, the health benefits of eating fish, such as its potential to lower the risk of heart disease, should also be considered.

Farmed salmon has higher levels of PCBs and other contaminants than wild salmon

Salmon is a popular fish, with about 23 million people eating it at least once a month. It is a good source of omega-3 fatty acids, which promote healthy vision and brain development in infants and reduce the risk of cardiovascular disease in adults. However, there is an ongoing debate about the safety of consuming farmed salmon due to concerns about contamination with pollutants such as PCBs.

PCBs, or polychlorinated biphenyls, are persistent, cancer-causing chemicals that were banned in the United States in 1976. They are one of the "dirty dozen" toxic chemicals slated for a global phase-out under the United Nations Convention on Persistent Organic Pollutants. While PCBs are no longer produced commercially, they persist in the environment and can accumulate in the food chain, including in fish like salmon.

Farmed salmon has been found to contain higher levels of PCBs and other contaminants than wild salmon. Studies have shown that farmed salmon contain five to 10 times the PCBs of wild salmon. For example, a study by Easton et al. (2002) found that the average level of total PCBs in ten farmed salmon samples was 27.3 ppb, which is 5.2 times higher than the average PCB level in four wild salmon samples. Other studies from Ireland, Scotland, British Columbia, and Alaska have also shown higher concentrations of PCBs in farmed salmon.

The higher levels of PCBs in farmed salmon are attributed to the use of fishmeal in their feed. Salmon are naturally carnivorous, and the traditional method of farming involves feeding them fishmeal made from smaller feeder fish, such as mackerel. These feeder fish live in the open ocean and can accumulate trace elements of PCBs, which are then passed on to the farmed salmon. While the salmon farming industry has explored alternatives to fishmeal, it is still a significant component of their feed.

The consumption of farmed salmon with high levels of PCBs poses potential health risks, particularly an increased risk of cancer. It is estimated that millions of people who regularly consume farmed salmon face an excess lifetime cancer risk due to PCB exposure. As a result, some health experts advise consumers to choose wild salmon, which is considered safer in terms of PCB contamination.

Salmon flesh can contain 9 million times more chemical residue than the water they live in

Salmon is a popular fish with well-documented health benefits, including being a great source of protein and omega-3 fatty acids, which are beneficial for the heart and brain. However, there are concerns about the contamination of salmon due to polluted water. Salmon migrate to the sea, where they pick up contaminants from the rivers that deposit in the ocean. Industrial and municipal discharges, agricultural practices, and stormwater runoff can introduce harmful substances into the water, which are then absorbed by the fish.

One particular concern is the presence of chemical residues in salmon flesh. Studies have shown that salmon can contain significantly higher levels of certain chemicals than the water they live in. In fact, it has been claimed that salmon flesh can contain up to 9 million times more chemical residue than the surrounding water. This is because contaminants can build up in the fish over time.

The specific chemicals of concern include polychlorinated biphenyls (PCBs), pesticides, antibiotics, and other toxins. PCBs, for example, are a probable carcinogen, and their levels have been found to be up to seven times higher in farmed Atlantic salmon than in wild salmon. Antibiotics used to treat parasites and pathogens in farmed salmon have also been detected in the fish, raising concerns about antibiotic resistance in humans.

The risk of exposure to these contaminants is particularly high for certain vulnerable populations, including infants, children, pregnant women, and women of childbearing age. This is because contaminants can be passed on to a developing fetus, and younger individuals are more susceptible to the potential harm from contaminants on their developing brains.

To minimize the risk of exposure to contaminants, it is recommended to choose wild salmon over farmed salmon, as wild salmon generally has lower levels of contaminants. Additionally, it is advised to eat smaller, younger fish and avoid eating the skin and fat of salmon, as contaminants tend to accumulate in these parts.

Salmon pick up contaminants from the rivers they migrate to

Salmon are an excellent source of omega-3 fatty acids, which promote healthy vision and brain development in infants and reduce the risk of cardiovascular disease in adults. However, concerns have been raised about the potential health risks associated with consuming contaminated salmon.

Salmon migrate to different rivers over their lifetime and can pick up contaminants from these waters. For example, Chinook salmon migrate to the sea, where they are exposed to contaminants from rivers like the Columbia, Washington's Puget Sound, British Columbia's Skeena and Fraser rivers, and California's Sacramento and San Joaquin rivers. The Columbia River, in particular, faces pollution threats from mining and toxic sludge from a tailings dam at British Columbia's Copper Mountain.

The contamination of salmon has raised alarms among tribal communities in the Pacific Northwest, who have a long history of relying on salmon as a staple food. In the 1990s, an EPA study found chemicals embedded in carp from the Columbia River, confirming the concerns of tribal elders who had noticed changes in the water quality. Subsequent testing by OPB and ProPublica revealed the presence of more than 92 different contaminants in the fish, some at levels high enough to pose risks to human health.

While the presence of contaminants in salmon is concerning, it is important to note that the risk is compounded by exposure to other toxic chemicals in the environment and other fish. Additionally, public health officials emphasize that the cancer risks associated with contaminated fish must be weighed against the well-known health benefits of including fish in one's diet.

Sea lice from farmed salmon can infect native populations

Sea lice are copepod crustaceans that have adapted to live on salmon, feeding on the fishes' skin and blood. They have a short, free-swimming larval phase, during which they need to find and attach to a fish host. In the wild, finding a host can be difficult due to their small size, but in aquaculture, where fish are kept in high densities, sea lice can easily exploit this and transmit diseases.

Sea lice infestations have been identified as a major cause for the decline in some wild Pacific salmon populations on the west coast of Canada. Data from 2007 to 2016 in the Muchalat Inlet region of Canada indicated a significant association between sea lice abundance on farms and the likelihood of wild fish becoming infested.

In the Broughton Archipelago, communities noticed that wild juvenile pink salmon were returning from their freshwater spawning grounds infested with sea lice. This was followed by an unprecedented decline in the number of wild pink salmon in 2002, which could not be explained by natural variations in salmon populations. Marine biologist Andrew Bateman attributed this to the presence of nearby salmon farms, which put the wild salmon at risk of infection.

To address the issue of sea lice, regulations in the United States and British Columbia require monthly monitoring of farmed salmon for sea lice and notification and treatment if sea lice numbers exceed three lice per fish. However, sea lice have built up resistance to commonly used chemical treatments, making it challenging to eradicate the pest completely.

Salmon is a good source of omega-3 fatty acids

Farmed salmon fillets contain similar or higher levels of omega-3 fatty acids compared to wild salmon because farmed salmon are generally fattier. However, the specific type of omega-3s found in salmon may vary. The omega-3s found in seafood are known as DHA and EPA, while ALA is the form of omega-3 found in plants. While ALA can be converted into DHA and EPA, this process is not very efficient, which is why dietary sources of DHA and EPA, such as salmon, are essential.

Salmon is considered one of the most nutrient-dense foods globally and is particularly high in omega-3 fatty acids. Regularly consuming fatty fish like salmon is associated with a lower risk of heart disease, dementia, and depression. Omega-3 fatty acids are also essential for healthy vision and brain development in infants. Additionally, salmon contains high-quality protein and various other nutrients, including vitamin D, selenium, and B vitamins.

While there are concerns about chemical contamination in salmon due to polluted waters, the Washington State Department of Health recommends eating two fish meals per week that are low in contaminants. Both wild and farmed salmon are considered safe, with low levels of mercury, PCBs, and other contaminants. The health benefits of consuming salmon are believed to outweigh the potential risks associated with contaminants.

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