Meghan Hodges
Fish are a crucial source of protein, vitamins, minerals, and omega-3 fatty acids, which are essential for human health. However, the presence of toxic pollutants in fish has become a growing concern for both human health and the environment. Fish absorb contaminants such as mercury, PCBs, PBDEs, dioxins, and chlorinated pesticides from water, sediments, and their food sources. Plastic pollution, in particular, has become a global crisis, with microplastics being ingested by fish at all levels of the food chain. As a result, humans who consume seafood are also inadvertently ingesting these microplastics, leading to potential health risks. Understanding the extent and impact of pollution consumption by fish is crucial for developing strategies to protect both human health and the delicate balance of aquatic ecosystems.
| Characteristics | Values |
|---|---|
| Percentage of fish species that ingest microplastics | 60% |
| Percentage of commercial fish species from Australia and New Zealand that contained microplastics | 75% |
| Average number of microplastic particles per fish | 2.5 |
| Percentage of plastic ingestion in sea turtles worldwide | 50% |
| Percentage of plastic ingestion in seabird species | 60% |
| Percentage of plastic ingestion in seabird species by 2050 | 99% |
| Percentage of fish at markets in California that contained plastic | 25% |
| Percentage of plastic ingestion in commercial fish species in Oregon | 99% |
| Percentage increase in the number of animal species that ingest microplastics since 1977 | 70% |
| Percentage of US seafood imported from regions with significant plastic waste leakage and pollution | 90% |
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What You'll Learn
Microplastics in fish
Microplastics are tiny pieces of plastic that float in the air, contaminate the food we eat, and the water we drink. They are a significant environmental problem, with plastic waste ending up in the oceans and being ingested by marine life. Fish consume microplastics at all levels of the food chain, from plankton to small fish, and on to predatory fish at the top of the food chain.
A study from Portland State University in Oregon found microplastics in 99% of samples from six common seafood species. Another study found microplastics in 180 out of 182 samples of seafood, either bought in stores or obtained from fishing boats. The highest levels were found in shrimp, with clothing or textile fibres representing over 80% of the substance detected.
The ingestion of microplastics by fish is a concern for human health. Fishery products are a significant source of microplastics in the human diet, and these microplastics can reach the gastrointestinal tract, causing oxidative stress, cytotoxicity, and translocation to other tissues. Microplastics can also release chemical substances, acting as carriers of microorganisms. These chemicals can be highly toxic and are linked to cancer, neurotoxicity, hormone disruption, and developmental toxicity.
Some studies have shown that smaller organisms, like shrimp and small fish, ingest more human-made contaminants like microplastics. This is because they are filter feeders and take in anything floating in the water column just below the surface. Microplastics have been identified in various fish species, including the Pacific United States' pink shrimp, pink snapper of southeastern Australia, zebrafish of Asia, and the crucian carp fish of Europe and Asia.
The presence of microplastics in fish poses a risk to human health, and it is important to address this issue at a policy level by reducing plastic use and implementing filters that catch microplastics in washing machines.
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Mercury contamination
Mercury enters water bodies through various pathways. A significant source is household and industrial waste incineration, as well as the burning of coal and other fossil fuels. Improper disposal of products containing mercury contributes as well. Once in the water, bacteria convert mercury to methylmercury, which is then consumed by plankton and small creatures, eventually making its way up the food chain to larger fish. This process, called bioaccumulation, results in larger, older fish having higher mercury levels.
The concentration of mercury in fish is influenced by several factors. Commercial fishing, the introduction of exotic species, and enhanced nutrient additions can trigger trophic disruptions, altering fish tissue MeHg concentrations. Climate change can also influence MeHg production and impact energy flow pathways, growth rates, and population size structures. Forest fires have been linked to increased mercury accumulation in fish by restructuring food webs and increasing mercury inputs.
Studies have shown that mercury levels in fish populations can decrease rapidly when experimental mercury loading is stopped. This suggests that controlling mercury emissions is crucial for reducing mercury contamination in fish. However, evaluating the recovery of contaminated fish populations due to specific Hg control measures is challenging due to the complex interplay of factors influencing mercury levels.
It is important to note that fish remain a nutritious part of a healthy diet, providing essential proteins, vitamins, minerals, and omega-3 fatty acids. The key is to choose fish with lower mercury levels and follow preparation and cooking methods that reduce exposure to contaminants.
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Industrial chemicals
Fish are often contaminated with industrial and agricultural pollutants, known as persistent organic pollutants (POPs). These include older chemicals such as DDT and mercury, as well as newer industrial chemicals like flame retardants, coolants, and plasticizers. While the concentrations of these pollutants in consumable marine fish vary, they are steadily declining.
Industrial activities contribute significantly to the presence of toxic chemicals in the environment, which subsequently contaminate fish. For instance, incineration, waste disposal, and intensive metallurgy release heavy metals like mercury, cadmium, and lead into the aquatic environment. These metals are toxic even at low concentrations when ingested over a long period.
Another group of industrial chemicals that contaminate fish is polychlorinated biphenyls (PCBs), which were historically used in electrical and hydraulic equipment. Although their production has been banned since 1979 due to their hazardous nature, PCBs persist in the environment and are commonly found in areas associated with electrical transformers and electronics recycling. When consumed by fish, PCBs accumulate in their fat and liver, leading to bioaccumulation as larger predators ingest contaminated smaller fish.
Dioxins, formed as unintended byproducts of incineration, pesticide production, and paper mill bleaching, are another class of industrial contaminants found in fish. These chemicals can collect in the fat tissue and liver of humans who consume contaminated fish, potentially causing immune system dysfunction, nervous system issues, and developmental problems.
The presence of industrial chemicals in fish highlights the need for regulatory strategies to reduce environmental contamination and protect consumer health. It also underscores the importance of regenerative approaches to industries like agriculture and aquaculture, as well as a transition away from fossil fuel extraction and the responsible management of chemical wastes.
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Plastic ingestion in wildlife
Plastic ingestion by wildlife is a significant environmental concern. Plastic waste, which often finds its way into oceans and onto beaches, poses a direct threat to various animal species. Marine organisms, including fish, crustaceans, mollusks, seabirds, sea turtles, seals, and other marine mammals, are particularly vulnerable to ingesting plastic debris.
Fish are known to consume microplastics at all levels of the food chain. Pellets, for instance, resemble fish eggs, leading some species to mistake them for food. Plastic can also be ingested indirectly when fish eat other fish that have already consumed plastic. A study in California found plastic in a quarter of commercial fish, while another study from Portland State University detected microplastics in 99% of samples from six common seafood species. Fish in the North Pacific ingest an estimated 12,000 to 24,000 tons of plastic annually, contributing to the transfer of plastic up the food chain.
The ingestion of plastic has detrimental health effects on marine life. Microplastics can cause cell damage, leading to mutations and diseases like cancer. They also disrupt oxygen molecule balance, resulting in reduced growth rates, increased disease susceptibility, reproductive issues, tissue damage, and impaired immune function. Additionally, plastic in the gastrointestinal tract can trigger false signals of fullness, leading to starvation. Gills clogged with microplastics hinder respiratory function, causing hypoxia.
Sea turtles, another victim of plastic ingestion, often mistake plastic sheeting and bags for their jellyfish prey. The ingested plastic can get stuck in their digestive system, creating a false sense of fullness, which can lead to starvation. Research indicates that half of the world's sea turtles have ingested plastic.
While the direct impact of plastic ingestion on wildlife is evident, the indirect consequences on ecosystems and human health are more complex. The bioaccumulation of plastic and associated chemicals in marine life can have unknown effects on human health when plastic-eating fish end up on dinner plates.
Overall, the growing presence of plastic in the environment, especially in oceans and on beaches, poses a significant threat to wildlife. The ingestion of plastic by marine organisms leads to health issues and even death, with certain species being more susceptible than others. While research is ongoing to understand the full scope of the problem, the immediate need is to address plastic pollution at its source to protect vulnerable wildlife and ecosystems.
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Human health impacts
Fish are exposed to microplastics even in the deepest depths of the ocean. These microplastics are often mistaken for food by fish, or are consumed when plastic mixes in with their food. As of 2016, microplastics have been found in 220 animal species, including fish, up nearly 70% since 1977.
Microplastics have been detected throughout the human body, including the brain, blood, and breast milk. They pose multiple threats to human health, including the functioning of our lungs, gut, and reproductive systems. Microplastics can enter the circulatory system by gastrointestinal absorption and direct inhalation, causing inflammation and dose-dependent accumulation in the human body. Fish consumption exposes the human body to microplastics through physical and chemical pathways like endocytosis and persorption.
Fish absorb contaminants such as PCBs, PBDEs, dioxins, and chlorinated pesticides from water, sediments, and the food they eat. PCBs can collect in a person's fat tissue and liver, and they can be transferred from mother to baby during pregnancy and breastfeeding. Long-term, low-level exposure to PCBs is associated with changes in normal immune system function, negative impacts on the nervous system, and developmental issues. PCBs are also classified as a probable human carcinogen by the US EPA.
Mercury is another contaminant that can be found in fish. It is a naturally occurring metal that is released into the environment from volcanic activity, mining, and the burning of fossil fuels. Mercury can build up in species as they go up the food chain in a process called bioaccumulation. Older, larger fish accumulate more contaminants than smaller, younger fish. High methylmercury exposure in children can cause developmental delays, cognitive deficits, and other health issues.
Other contaminants found in fish include arsenic, cadmium, lead, selenium, and chlorinated hydrocarbon pesticides. Arsenic is another naturally occurring metal that is released into the environment from mining, smelting, and the burning of fossil fuels. Increasing exposure to arsenic has been linked to adverse health effects, including several types of skin lesions and cancers, as well as impacts on the nervous system, respiratory systems, and heart health.
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Frequently asked questions
Fish across all oceans are found to consume plastic. A 2022 study found that three out of four commercial fish species from Australia and New Zealand contained microplastics in their edible flesh. Another study found microplastics in 99% of samples from six common seafood species. Fish in the North Pacific ingest 12,000 to 24,000 tons of plastic each year.
Plastic causes intestinal injury and death in fish and transfers up the food chain to bigger fish, marine mammals, and humans. Microplastics have been found to collect additional contaminants from their surroundings, posing threats to human health, including the functioning of our lungs, gut, and reproductive systems.
Fish absorb contaminants such as PCBs, PBDEs, dioxins, chlorinated pesticides, and mercury. Older 'legacy' chemicals such as DDT and newer industrial chemicals like flame retardants and coolants are also found in fish.
We should prevent the dumping and spilling of plastic pellets, reduce our use of single-use plastics, and bring reusable bags for shopping.
