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Effects of Air Toxics on Human Health

Anglers fishing Glacier Bay from shore at Glacier Bay National Park and Preserve, Alaska.
Fish consumption is the most important pathway for human exposure to toxic air contaminants.

Metals (such as mercury) and toxic compounds (like pesticides) can be deposited from the air and build up in the food chain causing behavioral, neurological, and reproductive effects in fish, birds, wildlife, and even humans.

What are toxics?

Air toxics include heavy metals like mercury, as well as persistent organic pollutants (POPs) like pesticides and DDT. These airborne contaminants are especially harmful, because they:

  • are long-lasting and do not breakdown in the environment,
  • can accumulate in tissues of organisms,
  • and have toxic effects.

Mercury in the food chain (Click figure to enlarge)

Mercury, PCBs, and pesticides can enter the food chain in areas impacted by air pollution. The National Park Service is concerned about these and other air toxics because they magnify in concentration with each level of the food chain and can pose serious health threats to wildlife and humans (see figure on the right). Although fish are a lean, low-calorie source of protein and are important in a healthy diet, consumption of fish is the most important pathway for human (and wildlife) exposure to mercury, pesticides, PCBs, and other contaminants.

How can air toxics affect your health?

The toxic form of mercury, methylmercury, impairs neurological development in fetuses, infants, and children. Other effects can include reduced reproductive success, impaired growth and development, behavioral abnormalities, reduced immune response, disease, and decreased survival.

The health effects of other air toxics vary. Some toxic compounds have been banned from use and production in the U.S.; however, these highly persistent compounds remain in the environment and fatty tissues of animals because they take long periods of time to break down. For example, dieldrin, an insecticide banned in the U.S. in 1987, is acutely carcinogenic and endocrine-disrupting. It also reduces the effectiveness of the immune system, reduces reproductive success, and causes neurological problems. DDT, an insecticide banned in the U.S. in 1972, is a known endocrine-disrupting compound. It is also a probable human carcinogen, damages the liver, temporarily damages the nervous system, reduces reproductive success, can cause liver cancer, and damages the reproductive system.


What are the symptoms of toxics exposure?

Symptoms vary widely and are largely dependent upon the toxic compound. Concerned citizens are encouraged to further explore this issue through health regulatory agencies including Agency for Toxic Substances and Disease Registry ( and Food & Drug Administration (


Who is at risk?

People who eat fish are most at risk for consuming metals and toxic compounds. However, certain groups of people are most at risk due to the toxic effects on fetal growth and childhood development. These groups include women of child-bearing age and children. Additionally, subsistence fish consumers, such as some native populations, are more at risk because they rely on fish for their primary diet.


How can I avoid unhealthy exposure?

The harm to humans from air toxics results from dietary ingestion, rather than airborne exposure. This is unlike human health concerns relating to other air pollutants including ozone and particulate matter.

The risks of adverse health effects are relatively low when fish are eaten periodically, as in recreational fishing. Risks can be minimized by following local fish advisories which will indicate the types of local fish that tend to have higher contaminants. Different restrictions may be applied to sensitive groups (such as women of childbearing age and children). Methylmercury is more likely to accumulate in the fish muscle, or fillet. Some fish preparation methods may influence other contaminant concentrations ingested, for example removing the skin from fish before cooking can reduce the amount of contaminants present. Some general recommendations for fish consumption and preparation to limit risk are:

  • When fishing, check the local fishing regulations and fish consumption advisories. If there are no guidelines, then you may want to eat smaller fish because they are likely younger and contain lower levels of harmful contaminants. The U.S. Environmental Protection Agency also posts National Listing of Fish Advisories (
  • If local fish advisories warn about contaminants that concentrate in the fatty portion of the fish (PCB, pesticides, dioxins, PBDEs) then consume less fatty fish or fish that that feed on the bottom of lakes and streams as they may have lower levels of these harmful contaminants.
  • When preparing fish, remove skin, fat, and organs where contaminants are more likely to accumulate.
  • Prepare fish by grilling, if possible, letting the fat drip off.


How do toxics/mercury affect national parks?

Airborne contaminants including mercury and pesticides have toxic effects that can harm human and wildlife health. Over 275 million annual visitors to U.S. national parks rely on the National Park Service to both provide opportunities for recreational activities such as fishing and observing birds and wildlife, and to care for all the natural resources, processes, and ecosystems within parks. Toxic air contaminants are transported to national parks from pollution sources as far away as Europe and Asia, and as near as the local county. Learn more »


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Last Updated: January 10, 2013