Meghan Hodges
Bioaccumulation is the process by which toxins enter and move up the food chain, building up in individual organisms. This occurs when an organism absorbs a substance faster than it can be metabolized, excreted, or eliminated by catabolism. Bioaccumulation is necessary for an organism's growth and development, but the accumulation of harmful substances can have adverse effects. Synthetic organic contaminants, heavy metals, and high levels of trace elements can enter an organism and affect its health. For example, turtles can be affected by PFAS, mercury, cadmium, argon, and selenium. Other contaminants that can bioaccumulate include pesticides, PCBs, PBDEs, DDT, and PBTs. These pollutants can have toxic effects on both humans and wildlife, impacting their health and development.
| Characteristics | Values |
|---|---|
| Definition | Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. |
| Occurrence | Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. |
| Factors influencing occurrence | Size, weight, age, sex, and class. |
| Related processes | Bioconcentration, biomagnification. |
| Examples of contaminants | Synthetic organic contaminants (e.g., PFAS), heavy metals (e.g., mercury, cadmium, lead, arsenic), Persistent Organic Pollutants (POPs) (e.g., DDT, PCBs, PBDEs), plastics, PBTs. |
| Impacts | Toxicity, metabolic issues, endocrine issues, developmental issues, cancer, neurological issues, reproductive issues, DNA damage, immune system damage. |
| Affected organisms | Turtles, phytoplankton, zooplankton, fish, birds, mammals, seals, orcas, humans. |
| Prevention | Governments are taking action to ban the production of harmful chemicals, such as the Stockholm Convention on Persistent Organic Pollutants. |
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What You'll Learn
Metals, such as lead, mercury, arsenic, cadmium, copper, tin, zinc
Metals are a significant source of concern when it comes to bioaccumulation and its adverse effects on the environment and living organisms. Heavy metals, in particular, are known to have detrimental impacts, with arsenic, cadmium, chromium, lead, and mercury ranking among the priority metals of public health significance. These metals are considered systemic toxicants, capable of inducing multiple organ damage even at lower levels of exposure. They are also classified as known or probable human carcinogens.
Arsenic, a ubiquitous element found in the environment, can cause acute toxicity or arsenicosis, leading to skin manifestations like pigmentation and keratosis. Arsenic poisoning can also result in pulmonary diseases, cognitive dysfunction, and neurological issues. Cadmium, ranked as the seventh most toxic heavy metal, is a by-product of zinc production, to which humans and animals may be exposed in their environment or workplace. Consequences of cadmium poisoning include degenerative bone disease, kidney failure, and gastrointestinal and lung diseases.
Lead, another toxic metal, has been linked to occupational carcinogenicity, with studies finding cancer in workers exposed to chromium. Mercury, meanwhile, plays a detrimental role in altering cellular function and structure, impacting processes such as transcription and translation, and causing free radical formation. Additionally, bioaccumulation of mercury can lead to mercury poisoning, as seen in the historical phrase "mad as a hatter," where hatters were exposed to mercury used in felt-stiffening.
Beyond these metals, copper, tin, and zinc are also of concern. Copper, for example, can have toxic effects when present in high concentrations, and zinc is a known essential nutrient that can be disrupted by the presence of other toxic metals. Furthermore, the accumulation of these metals in the environment, particularly in aquatic ecosystems, can result in bioaccumulation in organisms like turtles, affecting their health and development.
The bioaccumulation of metals is a complex issue, with potential synergistic or antagonistic interactions between different metals, making it challenging to fully understand the health impacts of metal mixtures. Additionally, the presence of plastics in the environment can further complicate the issue, as plastics can transport harmful pollutants and toxins to organisms. Therefore, understanding the dynamics of metal bioaccumulation is crucial for developing effective regulations and interventions to protect human beings, wildlife, and ecosystems from the adverse effects of metal exposure.
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Persistent Organic Pollutants (POPs) such as DDT and PCBs
Persistent Organic Pollutants (POPs) are a group of organic compounds, including pesticides, dioxins, furans, and polychlorinated biphenyls (PCBs). They are resistant to environmental degradation and can persist in the environment for extended periods, posing long-time exposure risks. POPs bioaccumulate in the food chain, gradually accumulating in the tissues of organisms, particularly in fatty tissues. This process, known as biomagnification, results in larger animals and humans at the top of the food chain having a higher risk of accumulating significant concentrations of POPs.
DDT, or 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane, is one of the most well-known POPs. It is a pesticide that has been widely used for disease and pest control, particularly in agriculture. DDT residues have been found in agricultural areas of all 23 countries in the Wider Caribbean Region, indicating its long-range transport within the region. DDT is restricted in its production and use, primarily allowed for disease-vector control. However, it continues to be used in sugar cane production and mosquito control in some parts of the world, affecting the health of millions of people.
PCBs, or polychlorinated biphenyls, are another significant POP. They have been detected in various environmental samples, including atmospheric, marine, freshwater, groundwater, sediment, soil, food, and even human blood and milk. PCBs have been widely used in industrial applications, such as electrical transformers and large capacitors, and as additives in paints and lubricants. The Convention on POPs prohibits new PCB production and aims to phase out electrical equipment containing high concentrations of PCBs.
Other POPs that have been identified as highly persistent and toxic include aldrin, chlordane, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene, and several others. These pesticides have been banned from agricultural use in many regions, but they continue to persist in the global environment. The presence of these POPs in the environment can have adverse effects on human health and ecosystems, making their management and reduction a global priority.
The bioaccumulation of POPs has been observed in various organisms, including turtles, seals, birds, and humans. For example, studies have detected high levels of PBDEs, another type of POP, in wildlife near e-waste recycling sites in China, suggesting heavy contamination in these regions. Understanding the dynamic processes of bioaccumulation is crucial for protecting humans and other organisms from the adverse effects of POP exposure. Initiatives such as the Commission for Environmental Cooperation (CEC) and the Stockholm Convention have been established to address the management and reduction of POPs on a global scale.
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Synthetic organic contaminants, e.g. PFAS
Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic chemicals, with over 1400 individual PFAS currently in use, and growing. PFAS are used in a diverse range of applications, from fast-food containers to anti-stain fabrics, firefighting foams, and industrial processes. PFAS are so prevalent that they have become emblematic of environmental contamination, and they are present everywhere from the Arctic to urban rainwater.
PFAS are extremely persistent in the environment and do not easily degrade due to the strength of the carbon-fluorine bond. PFAS molecules can persist on geologic time scales and bioaccumulate to toxic levels. PFAS are harmful to aquatic fauna, insects, and amphibians at concentrations of a few µg/L or less, and they accumulate in organisms and biomagnify in food webs.
PFAS can enter the bodies of organisms, including humans, through contaminated water or food, the use of products made with PFAS, or by breathing air containing PFAS. PFAS can also enter the body through the skin, for example, when PFAS-containing cosmetics are used. PFAS can then accumulate in the body when an organism absorbs the chemical faster than it can be lost through catabolism and excretion. This process is known as bioaccumulation and can lead to chronic poisoning.
Bioaccumulation of PFAS has been observed in both aquatic and terrestrial species, and it is a particular concern in turtles, where PFAS concentrations have been shown to impact the developmental metabolic processes and fat stores of turtle embryos. PFAS contamination has also been observed in alligators, and research is ongoing to understand the potential effects on the immune system.
The extreme persistence of PFAS in the environment and their potential for bioaccumulation mean that they are a significant cause for concern, and their use and presence in the environment need to be carefully monitored and regulated.
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Plastics, which can carry other toxins and block internal organs
Plastics are a major threat to the health of both humans and animals. Microplastics, which are particles smaller than 5mm that slough off plastic as it degrades, are now found in almost every bodily organ, including the blood, lungs, liver, kidneys, and placenta. They can enter the body through ingestion, inhalation, or even through the skin.
The danger of plastics lies not only in their physical presence, which can cause inflammation and the blockage of internal organs, but also in their ability to carry and deliver other toxins. Microplastics have been found to carry other environmental pollutants on their surface, acting as a “Trojan horse” to efficiently deliver these chemicals into the body. These pollutants include heavy metals, BPA, phthalates, and other toxic chemicals. Once inside the body, microplastics act as sustained-release vehicles, slowly releasing these toxins over the lifetime of the cells in the gut and other organs.
The full extent of the health risks posed by microplastics is still unknown, as it is a relatively new area of research. However, initial findings suggest that microplastics may be linked to growing rates of cancer, heart disease, and other chronic illnesses. They have also been found to cause inflammation, cell death, changes in the gut microbiome, and altered lipid and hormone metabolism.
The pervasiveness of plastic in the environment means that it is nearly impossible to avoid exposure. With the continued increase in plastic production and the ubiquity of microplastics, it is crucial that more research is conducted to fully understand the potential health risks and develop strategies to mitigate plastic pollution.
While the specific impacts of microplastics on human health are still being studied, the medical community is becoming more knowledgeable about plastic particle pollution and its potential link to various diseases and syndromes.
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PBTs, which can travel long distances and persist in ecosystems
Persistent Bioaccumulative and Toxic chemicals (PBTs) are extremely dangerous to humans and wildlife. They persist in ecosystems for extended periods without breaking down, then bioaccumulate and biomagnify. PBTs are mobile and can travel long distances, moving between air, water, and land.
DDT, a well-known PBT, was developed as a synthetic insecticide in the 1940s. It was sprayed on crops and eventually contaminated water bodies. Small organisms like plankton and algae absorbed DDT from the water, and the contamination moved up the food chain as larger predatory fish consumed the smaller fish. Despite being banned in the United States decades ago, DDT is still found in soil and water supplies today.
PBTs can have severe health impacts on humans and wildlife. They can cause mutagenic DNA damage, cancer, neurological issues, reproductive problems, developmental abnormalities, and immune system damage. The toxicity of a potential PBT chemical is determined by the EPA based on repeated exposures resulting in human or environmental toxicity.
Bioaccumulation is the process by which toxins enter the food web, building up in individual organisms. This occurs when an organism absorbs a substance faster than it can be eliminated through catabolism and excretion. Metals, such as lead, mercury, and arsenic, are always persistent because they are basic elements that cannot be further broken down or destroyed in the environment.
Biomagnification is the process by which toxins are passed from one trophic level to the next, increasing in concentration as they move up the food chain. This occurs when contaminated smaller organisms are consumed, and the toxins accumulate and magnify in the tissues and organs of larger animals.
PBTs, with their persistence, bioaccumulation, and ability to travel long distances, pose a significant threat to ecosystems and human health. Governments should take proactive measures to phase out these chemicals and mitigate their adverse effects.
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Frequently asked questions
Bioaccumulation is the process by which toxins enter the food web by building up in individual organisms. This occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion.
Some examples of contaminants that bioaccumulate include Persistent Organic Pollutants (POPs), pesticides, heavy metals, and synthetic organic contaminants (PFAS). POPs include DDT and PCBs, which are synthetic chemicals that do not easily break down in the environment and can build up in the fatty tissues of living organisms. Heavy metals such as mercury, lead, and arsenic are also persistent and can bioaccumulate in organisms.
Bioaccumulation occurs at the base of a food web, usually within primary producers like phytoplankton. These microscopic organisms absorb contaminants directly from the seawater, and the toxins build up in their tissues over time. Biomagnification then occurs when larger organisms feed on the contaminated phytoplankton, absorbing the contaminants into their own tissues at higher concentrations. This process continues up the food chain, with contaminants increasing in concentration at each trophic level.
Bioaccumulation can have a variety of negative impacts on organisms, including metabolic, endocrine, and reproductive issues. It can also lead to starvation, physical blockage of internal organs, and increased vulnerability to other diseases and infections. In some cases, bioaccumulation can result in toxic concentrations that can be fatal. Additionally, it can impact the survival and reproduction of organisms, threatening the biodiversity of ecosystems.
