Fish Consumption: Polluted Water's Health Risks

Fish are an important source of protein for many people, but consuming them can also mean ingesting pollutants and micro-particles such as microplastics, mercury, and PCBs. A 2023 study by the Environmental Working Group found that eating a single serving of freshwater fish could expose a person to toxic forever chemicals known as PFAS, which are linked to liver damage, high cholesterol, reduced immune responses, and cancer. These chemicals, developed in the 1940s for their resistance to water and heat, have built up over time in the environment and are now found in water bodies, soil, food, and even our bodies. The issue of contaminated fish disproportionately affects communities that rely on fishing for sustenance and cultural practices, highlighting the environmental injustice caused by industrial discharges of PFAS.

Fish farms and oceans are polluted, leading to contaminated fish

Fish farms, or aquaculture, have become increasingly common over the last 50 years, with more seafood now being produced from aquaculture than from wild catch. This has had a positive impact on the health of global fish stocks as it reduces the pressure on wild fish populations, which are finite and can decline if we catch fish faster than they can reproduce.

However, fish farms can also contribute to the pollution of oceans and, consequently, contaminated fish. Fish farms produce nutrient pollution from the production of feed and from uneaten feed and fish waste, which can be consumed by most aquatic ecosystems. While fish and shellfish farmers take precautions to prevent the transmission of disease-causing pathogens and parasites, fish farms can amplify and transmit diseases between farmed and wild fish, and introduce non-native pathogens and parasites when fish are transported. For example, farmed fish are reared at higher densities than in nature, increasing contact between fish and the potential for disease transmission.

In addition, while antibiotic use in aquaculture has decreased for some species due to better husbandry and vaccines, drugs, including antibiotics, are still used in some cases to treat specific conditions in farmed fish. These drugs must be approved by regulatory bodies, such as the U.S. Food and Drug Administration (FDA), which requires that they are safe for the environment and consumption.

Overall, while fish farms have helped to reduce the pressure on wild fish stocks, they can also contribute to ocean pollution through nutrient runoff and the transmission of diseases and parasites. This can ultimately lead to contaminated fish, which can have potential health risks for consumers.

Fish contain harmful mercury, PCBs, and PFAS

Fish are a great source of nutrients, but they can also contain harmful substances like mercury, PCBs, and PFAS. Mercury is a toxic heavy metal that can be found naturally in the environment and is released through industrial processes and natural events. It accumulates in fish through the food chain, with larger, predatory fish having higher mercury concentrations. This can lead to health issues in humans who consume these fish, especially vulnerable groups such as pregnant women, breastfeeding mothers, and young children.

Mercury levels in fish depend on the species and the pollution levels in their environment. Studies have shown that a significant number of fish from streams in the United States and the New Jersey shore had mercury levels higher than the recommended limit. Larger, longer-lived fish, such as shark, swordfish, and tuna, tend to have higher mercury levels as they eat many smaller fish, and mercury accumulates in their bodies over time through bioaccumulation and biomagnification.

In addition to mercury, fish can also contain harmful levels of PCBs (polychlorinated biphenyls) and PFAS (perfluoroalkyl substances). PCBs are industrial chemicals that were once widely used but have been banned in many countries due to their toxic effects on human health and the environment. PFASs are a group of man-made chemicals that have been used in a variety of industries since the 1950s. They are highly persistent in the environment and can accumulate in the bodies of fish and other wildlife, leading to potential health risks for humans who consume them.

One study investigated the accumulation of PFASs in wild fish from a highly urbanized region in the southeastern United States. The results showed that PFOS (perfluorooctane sulfonate), a specific type of PFAS, was the most abundant compound in the fish muscle and whole fish. PFOS levels exceeded wildlife protective guidelines in a significant percentage of the fish, raising concerns for the health of both humans and wildlife predators that consume these fish, such as dolphins.

The presence of harmful substances like mercury, PCBs, and PFAS in fish highlights the importance of moderating the consumption of certain fish species, especially those with high levels of these contaminants. While the nutritional benefits of fish are significant, it is crucial to be aware of the potential risks associated with consuming fish from polluted waters and to take steps to minimize exposure to these harmful substances.

Fish consumption is linked to neurological issues and cancer

Fish consumption has been linked to both an increased and decreased risk of certain cancers. A study by Cancer Causes and Control found a link between eating fish and skin cancer, specifically melanoma. The study, which included nearly 500,000 participants, found that those who consumed the most fish (about 2.6 servings per week) had a 22% higher rate of melanoma compared to those who ate the least fish (0.2 servings per week).

However, another study published in ScienceDirect found a decreased risk of certain cancers with fish consumption. This study suggested that even small amounts of fish consumption were associated with a reduced risk of several cancers, particularly those of the digestive tract, including the oral cavity, pharynx, and esophagus. Inverse trends were also observed for larynx, endometrial, ovarian, and multiple myeloma cancers.

In terms of neurological issues, fish consumption has been found to have potential benefits for brain health and cognitive ability. Studies have shown that consuming fish and omega-3 fatty acids may reduce age-related brain gray matter loss and improve brain structure. Additionally, fish intake has been linked to higher gray matter volumes in specific regions of the brain, including the hippocampus, precuneus, posterior cingulate, and orbital frontal cortex. These structural changes have been associated with improved cognitive ability and a potential reduction in the risk of cognitive deficits and dementia.

While the link between fish consumption and melanoma is intriguing, it is important to note that the largest known risk factor for melanoma is sun exposure, and dietary factors are not the primary cause. Additionally, the positive effects of fish consumption on cardiovascular health and other aspects of overall health may outweigh the potential risks associated with melanoma. As such, researchers are not recommending a change in fish consumption based on the current findings.

The EPA recommends limiting fish intake and trimming fatty areas

Fish are an important source of nutrients such as selenium, zinc, protein, vitamin B12, vitamin D, and omega-3 fatty acids. Eating fish is recommended for pregnant women and children for these reasons. However, it is important to be mindful of the type and amount of fish consumed due to the potential presence of contaminants and pollutants, such as mercury.

The EPA and FDA have issued recommendations regarding fish consumption, advising that it is generally safe to eat fish one to three times a week, depending on the type of fish and the individual's weight and caloric needs. The guidelines aim to balance the health benefits of fish consumption with the risks associated with exposure to contaminants.

The EPA specifically recommends limiting fish intake to a maximum of two to three servings per week, with the number of servings depending on the weight of the individual. For adults weighing less than 165 pounds, it is advised to consume smaller portions or just two servings of fish per week from the "Best Choices" category to maintain mercury intake within the recommended limits.

The "Best Choices" category includes fish that are lower in mercury, such as anchovies, Atlantic mackerel, catfish, clams, crab, flounder, haddock, salmon, sardines, shrimp, tilapia, trout, and whiting. These fish have lower levels of mercury and are considered safer options for regular consumption.

To further reduce potential exposure to contaminants, the EPA also recommends trimming the fatty areas of fish before cooking and consuming them. These fatty areas, such as the belly and skin, tend to accumulate higher levels of pollutants, including mercury and other chemical contaminants. By trimming these parts, individuals can reduce their direct consumption of these harmful substances while still benefiting from the nutrients that fish provide.

Communities relying on freshwater fish are disproportionately affected by chemical pollutants

While freshwater fish are a significant source of food and nutrition for many communities, they are also a source of exposure to chemical pollutants, which can have detrimental effects on human health. These contaminants, such as mercury, PFAS, PCBs, and dioxins, accumulate in the tissues of fish, particularly in the liver and fat, and can be transferred to humans through consumption.

Communities that rely heavily on freshwater fish as a primary source of nutrition are at a heightened risk of experiencing the adverse health impacts associated with these chemical pollutants. This is because the contaminants can bioaccumulate in the bodies of humans, leading to a buildup of toxins over time. The specific chemicals found in fish can vary, but they often include mercury, PCBs, and PFAS, which have been linked to a range of health issues.

PCBs, or polychlorinated biphenyls, are of particular concern due to their persistence in the environment and ability to biomagnify in the food chain. Despite being banned in 1979, PCBs are still prevalent in the environment due to their resistance to degradation. They are commonly found in areas with industrial activities, such as electrical transformer manufacturing and metal recycling facilities. When consumed by fish, PCBs tend to accumulate in the liver and fatty tissues, and they can be transferred to humans through the food chain. Long-term exposure to PCBs has been associated with adverse effects on the immune system, nervous system, and developmental processes.

Mercury is another significant contaminant found in freshwater fish. It originates from household and industrial waste, as well as the burning of fossil fuels. Mercury accumulates in fish through bioaccumulation, resulting in higher concentrations in larger, older fish. Mercury has been linked to severe health problems, particularly in developing fetuses and young children. It can also take a long time for mercury to be eliminated from the human body, with women in their childbearing years requiring up to 6-12 months to significantly reduce their mercury levels.

PFAS (per- and polyfluoroalkyl substances) are a group of man-made chemicals that have been used in a variety of industrial and consumer applications. These chemicals are highly persistent in the environment and can accumulate in the bodies of fish and other organisms. While the specific health effects of PFAS exposure are still being studied, they have been associated with various health concerns, and their presence in freshwater fish highlights the ongoing risk to communities that rely on these fish as a food source.

To address these issues, regulatory efforts, and initiatives are necessary to reduce the release of pollutants into the environment and protect vulnerable communities. This includes implementing stronger legislation, improving waste management practices, and focusing on reducing and phasing out toxic chemicals that pose risks to both human and environmental health. By taking proactive measures, communities relying on freshwater fish can be safeguarded from the disproportionate impacts of chemical pollutants and ensure a safer and more sustainable food source.

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