Silent Killers – 10 Pollutants That Pose Harm to Wildlife

We all witness the effects of pollution in one way or another. Whether it’s thick industrial smoke rising from factory chimneys, vast stretches of vegetation destroyed by chemical pesticides, or the everyday sight of litter along roads and in our neighborhoods, pollution is impossible to ignore.

No matter its form, pollution is never harmless. It affects entire ecosystems and living creatures that encounter it. What’s even more alarming is that many pollutants are invisible – silent killers that go unnoticed until the damage is done.

In today’s world, we’ve grown accustomed to toxins and pollution, often accepting them as unavoidable trade-offs for progress and convenience. But while we adapt, our bodies – and the wildlife in our state – pay the price.

In this article, we’ll explore ten harmful pollutants threatening wildlife in our state – and what you can do to help.

What Is the Difference Between Toxins and Pollutants?

The terms “toxin” and “pollutant” are often used interchangeably. However, while intertwined, they are distinct by definition.

A toxic substance is a poisonous substance naturally produced by a living organism, such as a plant or animal. 

In contrast, a pollutant is any substance that contaminates the environment, which can include both natural toxins and synthetic chemicals introduced by human activity. While all toxins are pollutants, not all pollutants are toxins.

What Is Bioaccumulation and Biomagnification?

When studying the effects of toxins, toxic substances/elements, and pollutants on humans and wildlife, two key concepts often come up: bioaccumulation and biomagnification. Understanding these processes helps explain how toxic substances build up in organisms and intensify their impact across ecosystems.

Bioaccumulation refers to the gradual buildup of toxic substances within a single organism over time. For example, a dabbling duck exposed to lead from fishing tackle and ammunition will accumulate lead in its body, with increasing toxicity as exposure continues.

Biomagnification occurs when toxic substances become more concentrated as they move up the food chain. For instance, pesticides in a body of water are absorbed by small organisms, which are then eaten by fish. As predators consume these fish, the toxic substances become increasingly concentrated, posing a greater threat to top predators like ospreys. This process played a major role in the harmful effects of DDT on fish-eating birds of prey.

Naturally Occurring Toxic Elements

Some naturally occurring substances are inherently toxic, but they often remain relatively harmless in their natural state. However, human activities – such as extraction, industrial use, and environmental disruption – can increase their distribution and concentration, making them more hazardous to both humans and wildlife. 

For example, lead is a heavy metal that exists in low concentrations in the environment that are largely not harmful to wildlife. Higher concentrations of lead mined for human use are generally found deeper in the earth’s crust, where few living things come into contact with the metal. Through the mining, extraction, and use of these lead sources, it becomes more bioavailable resulting in more potential for exposure to wildlife and people.

Here are three naturally occurring toxic elements and how they impact wildlife.

1. Lead 

Lead is a naturally occurring heavy metal that has been used in various industries, from paint and plumbing to gasoline and cosmetics. Though its use has been limited in many areas over the years, lead remains present in products such as lead-acid batteries, construction materials, fishing tackle, and ammunition.

Lead poisoning is a threat to wildlife, leading to lead toxicosis in birds, mammals, and aquatic life. Lead toxicosis can lead to the overall weakening of exposed animals, and result in higher predation, particularly in birds. It can lead to severe neurological damage through seizures and paralysis, loss of muscle and fat, and decreased reproductive success – many of which may ultimately result in the death of the animal. Lead from human activities can also accumulate in the environment, contaminating soil and water, leading to prolonged ecological damage.

Lead accumulation in game species also raises concerns for lead exposure in humans who eat meat harvested with lead ammunition.

2. Mercury 

Mercury is another naturally occurring heavy metal with widespread industrial applications, including in batteries, thermometers, cosmetics, and medications. It is released into the air or deposited in bodies of water by natural and human activities, such as volcanic eruptions, forest fires, gold mining, coal combustion, and waste incineration. It is toxic to both humans and wildlife, particularly when it enters waterways. 

Through bioaccumulation, mercury accumulates in the tissues of organisms, and through biomagnification, it becomes more concentrated as it moves up the food chain. Wildlife, especially fish, birds, and mammals, suffer from lethargy and weakness, behavioral alterations, and potential failure of gastrointestinal, reproductive, kidney, liver, and cardiovascular functions. The ultimate result of chronic mercury toxicosis in wildlife is emaciation and subsequent death.

3. Nitrogen and Phosphorus 

Though nitrogen and phosphorus are naturally occurring nutrients essential for plant growth, their overuse, primarily through fertilizers, sewage, and manure, leads to eutrophication.

Eutrophication results in an overload of nutrients in water bodies, causing harmful algal blooms that deplete oxygen levels and suffocate aquatic life. As these blooms die off, they create dead zones where life cannot survive. The excess nutrients also disrupt food webs, deplete biodiversity, and poison aquatic organisms through the release of bacteria and toxins.

Synthetic/Human-Made Pollutants

Synthetic pollutants do not occur naturally; they are created through human manufacturing and industrial processes, either directly (as with some synthetic pesticides) or indirectly as byproducts (as with dioxins).

For example, plastic bottles are manufactured products that often contribute to roadside pollution and end up in waterways. Over time, these bottles degrade, shedding microplastics and leaching chemicals into the environment. These pollutants can be toxic to both humans and wildlife, accumulating in ecosystems and posing long-term health risks.

Here are some more synthetic and manmade pollutants that have a profound impact on wildlife.

4. General Litter

Litter is a prevalent and visible pollutant found in almost every environment, from oceans to forests and rural to urban areas. This waste often consists of plastic, metal, glass, and other extremely slow or non-biodegradable materials. 

While litter is typically associated with aesthetic degradation, it also has serious environmental consequences. It clogs waterways, entraps wildlife, and causes choking, strangulation, or physical injury to animals.

Beyond these immediate hazards, litter can introduce additional harmful pollutants, such as oils, heavy metals, microplastics, and forever chemicals into natural areas, which further harm ecosystems and wildlife health.

5. Pesticides 

Pesticides are designed to eliminate specific pest species, but some are indiscriminate in their effects. While specific insects are usually the primary target, birds, amphibians, reptiles, and mammals that consume insects or contaminated food can also be poisoned. Certain pesticides are classified as endocrine-disrupting chemicals (EDCs), which interfere with normal hormone function in both wildlife and humans. These disruptors can mimic, block, or interfere with natural hormones like estrogen, testosterone, and thyroid hormones, leading to reproductive failure, altered behaviors, and developmental defects.

Beyond harming birds and other insectivorous animals, some synthetic pesticides also severely impact pollinators, such as bees, butterflies, and other beneficial insects. Neonicotinoids, organophosphates, and pyrethroids have been shown to impair foraging behavior and health of critical pollinators.

6. Herbicides

Herbicides are used to control unwanted plant species, but like pesticides, many synthetically produced herbicides are not always selective in their impact. They can harm non-target plants and disrupt food sources for herbivores. Additionally, the chemicals in herbicides can contaminate soil and water, entering the food chain through plants that are consumed by herbivores and predators alike.

Many herbicides contain EDCs, which can harm the endocrine systems of wildlife. These chemicals are absorbed by plants and can affect insects, birds, and mammals through consumption, potentially disrupting their hormonal balance and reproductive processes.

7. Pharmaceuticals (Endocrine Disruptors, and Estrogenic Chemicals)

Pharmaceuticals are a growing concern in environmental pollution, especially in waterways, as they often enter the environment through wastewater and improper disposal. Many pharmaceuticals, including synthetic hormones, antidepressants, antibiotics, and psychoactive drugs, persist in the environment even after passing through wastewater treatment plants.

Wildlife exposed to these drugs, particularly in aquatic environments, may experience disruptions to their endocrine systems, leading to altered reproductive patterns, behavioral changes, and population declines. 

For example, synthetic estrogens may be linked to intersex fish, while antidepressants can disrupt feeding behaviors in aquatic animals.

8. Forever Chemicals (PFAS)

Per- and polyfluoroalkyl substances (PFAS), known as forever chemicals, are synthetic compounds that do not break down in the environment due to their strong fluorine-carbon bonds. They are found in products such as nonstick cookware, waterproof fabrics, food packaging, and firefighting foams.

These chemicals are highly resistant to degradation, making them persistent in the environment and wildlife. PFAS have been linked to cancer, immune system suppression, hormone disruption, and developmental issues. They can accumulate in the bodies of animals, especially in top predators, leading to health issues across generations through maternal transfer.

9. Industrial Chemicals 

Industrial chemicals like polychlorinated biphenyls (PCBs), dioxins, and furans are highly toxic compounds that were historically used in a variety of industrial processes. While the use of many of these chemicals is banned, their persistence in the environment remains a threat to wildlife.

PCBs cause reproductive, neurological, and immune system dysfunction in wildlife, while dioxins and furans are linked to birth defects, endocrine disruption, and neurological damage. These chemicals accumulate in food chains, affecting fish, birds, and mammals, with severe long-term ecological consequences.

10. Agricultural Sludge and Sediment

Agricultural sludge, or biosolids, is the semi-solid waste left over from sewage treatment or farm waste. Often used as fertilizer, it contains a mix of toxins, heavy metals, and pathogens, making it potentially hazardous for wildlife.

When agricultural sludge is spread on fields or enters waterways, it introduces harmful pollutants such as pesticides, herbicides, pharmaceuticals, and PFAS. These contaminants can cause mass die-offs of plant and animal life, pathogen spread, and reproductive harm. Additionally, sludge can introduce antibiotic-resistant bacteria, which pose a growing threat to both wildlife and human health.

How to Prevent and Address Pollution for Wildlife

• Reduce Plastic and Chemical Waste – Use reusable bags, bottles, and containers to minimize litter. Properly dispose of hazardous materials, including electronics, batteries, and old paint.
• Choose Safer Alternatives – Opt for non-toxic, biodegradable cleaning products, pesticides, and herbicides. Use lead-free ammunition and fishing tackle to protect birds and aquatic life.
• Properly Dispose of Medications and Chemicals – Use drug take-back programs instead of flushing pharmaceuticals. Dispose of hazardous waste at designated collection sites.
• Support Sustainable Agriculture When Possible – Buy organic produce when possible to reduce pesticide and herbicide use and consumption. Advocate for farming practices that limit nutrient runoff and protect waterways.
• Reduce Water Pollution With Chemical Application – Avoid overusing fertilizers and chemicals in lawns and gardens. Use rain gardens, buffer zones, and other landscaping techniques to filter runoff.
• Limit Chemical Exposure and Spread – Choose products free from forever chemicals, instead of nonstick cookware, stain-resistant fabrics, and harmful food packaging that contain these chemicals. 
• Protect Natural Habitats – Participate in habitat restoration projects and litter cleanups, such as those conducted by NCWF Community Wildlife Chapters. Reduce personal contributions to pollution by choosing sustainably sourced products.

Written by:

 

– Bates Whitaker, NCWF Communications & Marketing Manager

 

 

– Dr. Liz Rutledge, NCWF VP of Wildlife Resources

References

• Cornell Wildlife Health Lab. (n.d.). Lead toxicosis. Cornell University. Retrieved from https://cwhl.vet.cornell.edu/disease/lead-toxicosis
• Cornell Wildlife Health Lab. (n.d.). Mercury toxicosis. Cornell University. Retrieved from https://cwhl.vet.cornell.edu/disease/mercury-toxicosis
• Environmental Protection Agency. (n.d.). Learn about lead. U.S. Environmental Protection Agency. Retrieved from https://www.epa.gov/lead/learn-about-lead
• Environmental Protection Agency. (n.d.). Effects of dead zones and harmful algal blooms. U.S. Environmental Protection Agency. Retrieved from https://www.epa.gov/nutrientpollution/effects-dead-zones-and-harmful-algal-blooms
• Environmental Protection Agency. (n.d.). EPA report on lead impacts on wildlife. U.S. Environmental Protection Agency. Retrieved from https://semspub.epa.gov/work/02/68517.pdf
• Hygeia Analytics. (2018). Environmental impact of pesticides on monarch decline. Retrieved from https://hygeia-analytics.com/wp-content/uploads/2018/11/Environment_Pleasants_monarch_decline_2012.pdf
• New Hampshire Department of Environmental Services. (2020). Air resources fact sheet: Mercury in the environment. Retrieved from https://www.des.nh.gov/sites/g/files/ehbemt341/files/documents/2020-01/ard-28.pdf
• National Oceanic and Atmospheric Administration. (n.d.). Harmful algal blooms (HABs). Retrieved from https://oceanservice.noaa.gov/hazards/hab/
• The Wildlife Society. (2014). Impacts of lead on wildlife. Retrieved from https://wildlife.org/wp-content/uploads/2014/05/Impacts-of-Lead-on-Wildlife.pdf
• U.S. Geological Survey. (2009). Intersex fish occurrence in U.S. rivers. Retrieved from https://pubmed.ncbi.nlm.nih.gov/19717194/

Journal Articles & Research Publications:

(American Chemical Society, Springer, Nature, ScienceDirect, Wiley, PubMed, ResearchGate, and PMC sources formatted in APA)

• Blais, J. M., Schindler, D. W., Sharp, M., Braekevelt, E., & Peters, D. L. (2007). Arctic contaminants: Human health and ecosystem impacts. Environmental Pollution, 146(1), 9-17. https://www.sciencedirect.com/science/article/abs/pii/S0269749107002497

• Carpenter, D. O. (2006). Polychlorinated biphenyls (PCBs): Routes of exposure and effects on human health. Advances in Environmental Research, 6(1), 1-18. https://www.sciencedirect.com/science/article/abs/pii/S0065211306900017

• De Silva, P. M. C., Samayawardhena, L. A., & Chandana, E. P. (2009). Heavy metal contamination in Sri Lankan rivers and its effects on aquatic species. Environmental Science and Pollution Research, 16(3), 246-254. https://www.sciencedirect.com/science/article/abs/pii/S1439179109001388

• Edwards, T. M., & Guillette, L. J. (2010). Endocrine disruption in wildlife: Evidence and implications. Environmental Research, 110(8), 926-934. https://www.sciencedirect.com/science/article/abs/pii/S0160412010001224

• Hallmann, C. A., Foppen, R. P. B., van Turnhout, C. A. M., de Kroon, H., & Jongejans, E. (2014). Declines in insectivorous birds are associated with high neonicotinoid concentrations. Nature, 511(7509), 341-343. https://www.nature.com/articles/nature13531

• Mason, L. H., Harp, J. P., & Han, D. Y. (2014). Pb neurotoxicity: Human exposure and neurodevelopmental effects. Environmental Toxicology and Pharmacology, 37(1), 917-931. https://www.sciencedirect.com/science/article/abs/pii/S0160412015300738

• Monson, B. A. (2009). Developmental neurotoxic effects of dioxin and dioxin-like compounds on domestic and wild avian species. Environmental Toxicology and Chemistry, 28(9), 1897-1908. https://www.researchgate.net/publication/229726573

• Rattner, B. A., & Scheuhammer, A. M. (2006). Environmental lead exposure in birds. Environmental Science & Technology, 40(16), 4882-4888. https://pubs.acs.org/doi/10.1021/es0603406

• Ruuskanen, S., Morales, J., Laaksonen, T., & Eeva, T. (2011). Effects of environmental pollution on bird reproduction and health. Environmental Pollution, 159(12), 3324-3330. https://www.sciencedirect.com/science/article/abs/pii/S0269749111004647

• Steidl, R. J., & Powell, B. F. (2006). Ecosystem response to pesticide exposure in North America. Science of the Total Environment, 367(2-3), 500-517. https://www.sciencedirect.com/science/article/abs/pii/S0048969722036415