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Toxic Chemicals in Puget Sound

Harmful Effects of Chemicals of Concern

Which toxic chemicals in Puget Sound are most dangerous? This isn’t an easy question to answer since different chemicals cause harm in different ways and to different organisms. The hazard any given chemical poses depends on how toxic it is and how much enters the Puget Sound environment.

Some toxic chemicals don’t break down easily in the environment, and they can move up through the food chain. These “persistent, bioaccumulative” toxic chemicals can build up in the tissues of small organisms living in Puget Sound. These tiny living things are eaten by fish, which in turn are then eaten by larger fish, marine mammals, and sometimes humans – harming their health.

Recent studies by NOAA Fisheries and the U.S. Fish and Wildlife Service have found that Coho salmon are dying prematurely in large numbers when they return from the ocean to spawn in Puget Sound’s urban streams. Although the precise cause of these die-offs is not yet known, toxic chemicals in polluted surface water runoff likely play a role.

Research has identified the following specific harmful effects of toxic chemicals:


Arsenic and many of its compounds are especially potent poisons. Many water supplies close to mines are contaminated by these poisons. Arsenic causes harm by disrupting metabolism at the cellular level. Arsenic can cause fetal death and malformations in many mammal species.


Cadmium can be acutely toxic to freshwater organisms. While marine organisms are more resistant to cadmium, shellfish can concentrate cadmium in levels that are harmful to people who eat them.


Copper is a special concern. While people may not be harmed by small amounts of copper, even low levels of the chemical are a significant threat to salmon and other fish in Puget Sound. Copper interferes with salmon’s sense of smell, which reduces their ability to avoid predators, find their way back to their birthplace to spawn, and find mates.


Lead is a natural element in the environment but most lead-related health and environmental problems are the result of human activities. Lead is present in Puget Sound from past uses such as when lead was added to gasoline, household products like ammunition, and uses in some occupations like specialty glass manufacturing. Lead is a known persistent bioaccumulative toxic chemical which means past uses can continue to expose people and other organisms. Lead can impair brain development and learning in children and can affect behavior, high blood pressure, reproduction, and growth in both children and adults. Lead similarly affects animal species. Waterfowl are particularly at risk to lead shot if they ingest it while feeding.


Mercury is very toxic. It is mostly known as a neurotoxin, meaning that it harms the brain and nervous system. However, mercury is also linked to kidney and liver damage and possibly cancer. Children are especially at risk because of their brains and bodies are still developing. Many of the health effects of mercury can be permanent. When it rains, airborne mercury deposits back on the land and water bodies that drain to Puget Sound. Some of the mercury is converted into methyl mercury, a highly stable compound that contaminates our water and our marine life. The methyl mercury concentrates up the food chain, especially in certain fish where it can affect the health of people who eat them. Infants, children and pregnant or nursing mothers must take special precautions to minimize mercury exposure from fish.


Zinc can kill young salmon as they swim out of their nest gravel. In high enough concentrations, zinc can kill many adult fish species.

PAHs (polycyclic aromatic hydrocarbons)

PAHs in the bottom sediments of Puget Sound can cause tumors in marine flatfish. PAHs from oil and fuel spills in water can cause heart defects in the developing embryos of herring and other fish species.

Petroleum-related compounds

Petroleum-related compounds – including gasoline, motor oil, hydraulic fluids, diesel and jet fuels – are mixtures of many different chemicals, including additives. Many petrochemicals are toxic to algae and invertebrates. They can cause changes in metabolism, reduced feeding, and poor shell formation. These compounds can poison fish at all life stages and kill their eggs and larva. They can damage the skin, lungs, liver, and kidneys of birds and mammals as well as increase vulnerability to deadly infections by suppressing the immune system. Petrochemicals can reduce the reproductive success of invertebrates such as shellfish and insects, fish, birds, and mammals, leading to population declines. They can also damage plants and impair or stop seed germination.

PBDE flame retardants (polybrominated diphenyl ethers)

PBDE flame retardants can affect the development, reproduction, and survival of many species. They build up in the food chain and are found in people as well other organisms including fish and orcas in Puget Sound.

Phthalates (including DEHP or bis(2-ethylhexyl) phthalate)

Exposure to DEHP, a phthalate, is associated with developmental and reproductive harm, especially the male reproductive system in humans and animals.

PCBs (polychlorinated biphenyls)

PCBs build up in the food chain and can cause adverse health effects in humans and wildlife, including cancer and harm to immune, nervous, and reproductive systems. PCBs disrupt thyroid hormone levels in animals and humans, hindering growth and development.

DDT (dichlorodiphenyltrichloroethane)

The pesticide DDT builds up in the food chain and can last for decades in the environment. DDT is linked to the decline of the bald eagle, peregrine falcon, and other birds because it makes their egg shells too thin, decreasing the survival of chicks.

PCDD/Fs dioxins (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans)

Even at very low concentrations, PCDD/F dioxins are toxic to humans and animals. Dioxins can cause cancer, disrupt the endocrine (hormone) system, and harm reproduction and development. While birds and mammals are at greater risk than fish, dioxins build up in the food chain and may affect people and animals that eat fish


In the waters draining to Puget Sound, levels of the weed killer triclopyr are typically below concentrations where they cause environmental harm. If misapplied, however, triclopyr can harm fish and other aquatic species.


Nonylphenol, a chemical found in detergents, is thought to mimic estrogen compounds, reducing reproduction in aquatic organisms.

For more information, see Loading Quantities

Assessment of Selected Toxic Chemicals in the Puget Sound Basin

Assessment of Selected Toxic Chemicals in the Puget Sound Basin: 2007—2011

Focus on Puget Sound: Puget Sound Toxics Assessment

Frequently Asked Questions