- Non-biodegradable pollutants are substances that cannot be broken down by natural biological processes.
- Examples include polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), and mercury.
- These pollutants persist in the environment for decades, becoming toxic hazards that accumulate in organisms and magnify through food chains.
- These pollutants affect ecosystems through two main processes -bioaccumulation and biomagnification.
Non-biodegradable pollutants remain chemically stable and resistant to microbial breakdown, which makes them particularly dangerous to long-term ecosystem health.
Bioaccumulation
Definition
Bioaccumulation
Bioaccumulation refers to the process by which the concentration of non-biodegradable pollutants increases in an organism over time.
- Bioaccumulation occurs when an organism absorbs a pollutant faster than it can excrete it.
- Pollutants enter organisms through:
- Direct absorption from water or soil.
- Ingestion of contaminated food or prey.
- Respiration (in the case of volatile pollutants).
- Over time, this results in increased internal concentrations, especially in long-lived organisms.
- Fish living in contaminated rivers can accumulate mercury in their muscle tissue.
- Even if mercury levels in the water are low, the continuous exposure over the years leads to significant buildup within the fish.
Biomagnification
- Biomagnification refers to the progressive increase in pollutant concentration at successive trophic levels of a food chain.
- At each step, consumers ingest the accumulated pollutants from their prey. Since these pollutants are non-biodegradable and fat-soluble, they are retained and further concentrated in their tissues.
- As a result, top predators exhibit the highest concentrations of toxic substances.
- Think of biomagnification like a snowball effect.
- Small concentrations of pollutants at the base of the food chain accumulate and intensify as they move upward.
Mercury and Minamata Disease
- In 1956, industrial discharge of mercury into Minamata Bay (Japan) caused one of history’s worst pollution disasters.
- Bacteria converted mercury into methylmercury, a highly toxic form.
- Fish absorbed methylmercury, and humans eating the fish developed severe neurological disorders.
- Over 2,000 people died or were permanently disabled.
Environmental and Biological Consequences
- Top predators (e.g., eagles, seals, humans) are most at risk.
- Persistent pollutants can cause:
- Reduced reproductive success (e.g., eggshell thinning)
- Neurological and developmental damage
- Hormonal imbalances and carcinogenic effects
- Disruption of aquatic and terrestrial food webs
- Bioaccumulation= accumulation within one organism or trophic level.
- Biomagnification= increase along successive trophic levels.
- Mercury and DDT are both persistent organic pollutants (POPs), but mercury is an inorganic heavy metal, while DDT is an organic pesticide.
- Both are non-biodegradable and biomagnify through food webs.
Microplastics and Non-biodegradable Pollutants
Definition
Microplastics
Microplastics are small plastic particles, typically less than 5 millimeters in diameter, that result from the breakdown of larger plastic waste or are intentionally manufactured at that size.
- Microplastics are non-biodegradable and can persist in marine and terrestrial ecosystems for centuries.
- When combined with other persistent organic pollutants (POPs), microplastics act as vectors, absorbing and transporting harmful chemicals through food chains.
How Microplastics Spread Pollutants
- Absorption of Pollutants: Microplastics have large surface areas and hydrophobic properties, allowing them to attract and bind pollutants like PCBs, pesticides, and heavy metals.
- Ingestion by Marine Life: Plankton, shellfish, and fish mistake microplastics for food, ingesting them directly.
- Transfer Through the Food Chain: Polluted microplastics pass from prey to predator, increasing pollutant concentration through biomagnification.
- Human Exposure: Humans ingest microplastics and associated pollutants through seafood, table salt, and drinking water.
A 2019 study found that oysters exposed to microplastics containing pollutants had reduced feeding rates, slower growth, and decreased reproduction, impacting the population’s long-term sustainability.
