Helena Joyce
Fish are incredibly susceptible to the harmful effects of pollution. When large quantities of pollutants are released, it can cause large-scale sudden mortalities of aquatic organisms. Lower levels of discharge may result in an accumulation of pollutants in aquatic organisms, leading to immunosuppression, reduced metabolism, and damage to gills and epithelia. Fish absorb contaminants such as PCBs, PBDEs, dioxins, chlorinated pesticides, and heavy metals like mercury from water, sediments, and the food they eat. These contaminants can build up in the bodies of fish and result in health problems. Microplastics, which are found in drinking water and other foods, are another significant source of pollution that can harm fish.
| Characteristics | Values |
|---|---|
| Types of pollution | Heavy metals, pesticides, hydrocarbons, microplastics, PCBs, PBDEs, dioxins, chlorinated pesticides |
| Sources of pollution | Industrial and municipal discharges, agricultural practices, storm water runoff, rain, landfill, incinerators, sewage treatment facilities |
| Impact on fish | Disease, lesions, rot, immunosuppression, reduced metabolism, damage to gills and epithelia, liver damage, infant development problems, reproductive issues, abnormalities |
| Impact on humans | Health problems, infant development issues, changes in blood, liver and immune functions |
| Prevention | Reduce use of plastics, use reusable containers and utensils, eat smaller and younger fish, avoid eating fish skin and fat |
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What You'll Learn
- Fish ingest microplastics, which cause adverse health effects
- Heavy metals and pesticides cause severe destruction to fish
- Fish absorb contaminants such as PCBs, PBDEs, and chlorinated pesticides
- Mercury bioaccumulates in fish, causing health problems in humans
- Fish diseases are more common in polluted marine sites
Fish ingest microplastics, which cause adverse health effects
Microplastics can release chemical substances (organic and inorganic) that have built up in their matrix or have been absorbed from the environment. These chemicals can cause oxidative stress, cytotoxicity, and the translocation of toxins to other tissues. Mercury, lead, zinc, copper, and cadmium present on marine microplastics can lead to the co-selection of antibiotic-resistant human pathogens.
The impact of microplastics on fish health is a growing area of research. It is known that microplastics can affect the ability of fish to ward off viruses, with fish exposed to microplastics dying more often when exposed to a deadly fish virus. This has implications for the health of both fish and humans, as humans consume fishery products that may contain microplastics.
The mass production and consumption of plastics have led to their accumulation in natural habitats, with negative impacts on biota and the economy. Plastic production is expected to double by 2025 and more than triple by 2050. This will inevitably lead to an increase in microplastics in aquatic environments, which will affect fish health and, consequently, human health.
Overall, the ingestion of microplastics by fish has been shown to have adverse health effects, including impaired growth, reproductive issues, and increased mortality. The presence of microplastics in fish habitats poses a significant risk to the health and well-being of marine ecosystems and highlights the need for proactive measures to mitigate the release of microplastics into the environment.
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Heavy metals and pesticides cause severe destruction to fish
Heavy metals and pesticides have a detrimental impact on fish, causing severe destruction to their health and contributing to wider ecosystem degradation. The release of these pollutants into aquatic environments poses significant risks to fish populations and, subsequently, to human health.
Heavy metals are discharged into aquatic ecosystems through industrial effluents, wastewater disposal, and agricultural practices. These metals, including arsenic, cadmium, chromium, copper, iron, mercury, nickel, lead, and zinc, accumulate in the tissues of fish, leading to toxic effects. Fish absorb these metals through their gills, liver, kidneys, skin, and muscles, disrupting their normal physiological functions. The bioaccumulation of heavy metals in fish results in reduced growth, impaired reproduction, and energy loss. For example, exposure to nickel chloride caused irregular swimming behaviour and respiratory illness in Nile tilapia.
Pesticides also play a significant role in the destruction caused by pollution to fish populations. They enter marine ecosystems through runoff, direct application, and atmospheric deposition. Long-term exposure to pesticides results in abnormalities and mutations in developing fish larvae, which are administered through their parents. Pesticides contaminate organic matter in water, which is the primary food source for aquatic food webs, leading to ecosystem degradation and disease. Additionally, pesticides can settle at the bottom of water bodies, causing bottom-dwelling fish to have high levels of these chemicals in their systems.
The impact of heavy metals and pesticides on fish is further exacerbated by their ability to bioaccumulate in the food chain. Larger, older fish accumulate more contaminants than smaller, younger fish. This bioaccumulation leads to higher concentrations of toxins in top predators, including humans, which can result in health issues such as infant development problems and immune system dysfunction.
The pollution caused by heavy metals and pesticides in aquatic ecosystems has severe consequences for fish populations, affecting their growth, development, behaviour, and overall health. These pollutants also contribute to the degradation of aquatic environments and the reduction of freshwater supplies, posing risks to both aquatic life and human well-being.
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Fish absorb contaminants such as PCBs, PBDEs, and chlorinated pesticides
Fish are directly and indirectly impacted by contaminants such as PCBs, PBDEs, and chlorinated pesticides. PCBs (polychlorinated biphenyls) are a group of man-made chemicals that were previously used as insulating fluids in electrical equipment. Despite being banned internationally, PCBs continue to be detected in the environment, including in water bodies. Fish become contaminated with PCBs by living near contaminated sediment or by consuming contaminated prey. Over time, PCBs accumulate in the fatty tissues of fish, with levels thousands of times higher than the concentration in the water, particularly in bottom-feeding and predatory fish. PCBs have been linked to adverse health effects in humans, including potential carcinogenicity, neurodevelopmental impacts, and effects on the immune, endocrine, and reproductive systems.
PBDEs (polybrominated diphenyl ethers) are flame retardants historically used in polymers to prevent or slow the spread of fires in products like padding, furniture, and electronics. PBDEs have become ubiquitous environmental contaminants due to their broad usage, ability to migrate from polymers, and the tendency of products to degrade into micro- and nano-plastics. PBDE levels in fish from certain U.S. sites with historical contamination have been found to exceed the environmental quality standards set by the European Parliament. Regulatory agencies should continue monitoring PBDE levels to protect human health and the environment.
Chlorinated pesticides are another contaminant impacting fish. Pesticides can enter water bodies through runoff from agricultural fields, especially after heavy rains, leading to pesticide contamination. Fish larvae exposed to pesticides through water contamination can develop swimming abnormalities, making them more vulnerable to predators and affecting their survival rates. Pesticides can alter various aspects of a fish's physiology, including histology, hematology, defence mechanisms, and behaviour. Additionally, pesticides can cause immediate impacts, such as large-scale mortalities of fish, or accumulate in aquatic organisms over time, resulting in immunosuppression, reduced metabolism, and damage to gills and epithelia.
The presence of these contaminants in fish can have significant ecological and human health implications. It is crucial to address the sources of these contaminants and implement measures to reduce their release into the environment to mitigate their impact on fish populations and the potential risks to human health through the food chain.
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Mercury bioaccumulates in fish, causing health problems in humans
Mercury is a naturally occurring element that can be released into the environment through volcanic activity, the weathering of rocks, and human activity. Human-related sources of mercury include coal combustion, chlorine alkali processing, waste incineration, and metal processing. Mercury is a contaminant that can be absorbed by fish, leading to health problems in humans who consume them. This process is known as bioaccumulation, where organisms, including humans, take up contaminants faster than their bodies can eliminate them, resulting in a buildup of toxins over time.
Bioaccumulation of mercury in fish occurs because fish efficiently absorb methylmercury but excrete it very slowly. Methylmercury is produced when bacteria in the water convert mercury into this organic compound. This methylmercury is then absorbed by algae at the start of the food chain, which is consumed by small fish and other organisms, transferring the toxin up the food chain. Larger, older fish that are higher in the food chain, such as marlin, tuna, shark, swordfish, king mackerel, and tilefish, tend to accumulate higher concentrations of mercury.
The consumption of fish is the most significant source of ingestion-related mercury exposure in humans. When people eat fish containing methylmercury, they are exposed to this toxic compound. The accumulation of mercury in the human body can lead to health issues such as kidney and nervous system damage, skin problems, and neurological and behavioural disorders. Studies have shown that high levels of mercury in fish can impact human health, with children born in coastal Colombia during periods of high mercury content in fish exhibiting worse educational and labour market outcomes.
The effects of mercury bioaccumulation in fish on human health are of particular concern for vulnerable populations, such as pregnant women and their unborn children. Exposure of the fetus to methylmercury poses dangers to the developing child, and pregnant women are advised to avoid consuming fish with high mercury levels. Additionally, populations that consume whale meat, such as the Japanese, Icelanders, Norwegians, and the Faroese, are also at risk due to the bioaccumulation of mercury in cetaceans (whales and dolphins).
To mitigate the health risks associated with mercury-contaminated fish, it is recommended to consume a variety of fish known to have lower mercury levels and to follow statewide mercury advisories, especially for women who are pregnant or planning to become pregnant, nursing mothers, and young children. While fish is a nutritious source of protein, vitamins, and omega-3 fatty acids, it is important to be mindful of the potential presence of contaminants like mercury and make informed choices to maintain a balanced and healthy diet.
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Fish diseases are more common in polluted marine sites
Water pollution can cause a range of non-infectious disorders in fish, including immunosuppression, reduced metabolism, and damage to gills and epithelia. Pollutants can also bioaccumulate in fish tissues, leading to organ dysfunction, irreversible cell damage, and an increased risk of tumors. High concentrations of certain pollutants, such as copper, have been linked to specific diseases, making fish more susceptible to infections.
For example, surface lesions have been attributed to Serratia plymuthica, which may be caused by contaminated domestic sewage. Fin and tail rot, caused by Aeromonas hydrophila and Pseudomonas fluorescens, have also been observed more frequently in polluted waters. Vibriosis, caused by Vibrio anguillarum, is another disease associated with high concentrations of copper in the water.
In addition to copper, pollutants such as pesticides, heavy metals, and hydrocarbons are often released into aquatic environments. These substances can have lethal effects on fish, leading to large-scale mortalities. Lower levels of these pollutants can accumulate in aquatic organisms over time, resulting in adverse health outcomes.
Pollution can also alter the aquatic environment by decreasing dissolved oxygen levels, changing the pH of the water, and introducing toxic chemicals. These changes can be detrimental to the health of fish, further contributing to the increased prevalence of diseases in polluted marine sites.
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Frequently asked questions
Large-scale sudden mortalities of aquatic organisms, including fish, can occur due to high levels of pollutants in the water.
Fish that survive in polluted waters can experience immunosuppression, reduced metabolism, damage to gills and epithelia, and the development of abnormalities.
Pollution enters water bodies through industrial and municipal discharges, agricultural practices, stormwater runoff, and even rainfall that washes chemicals from the land or air into water bodies.
Heavy metals and pesticides are particularly destructive to fish and other aquatic organisms. Microplastics are also a significant concern, as they are ingested by fish and can have adverse health effects.
