U.S. Fish & Wildlife Service

Pollution & Wildlife

What Are Contaminants?

Contaminants are toxic substances that can harm fish, wildlife, plants and people. Some environmental contaminants (including mercury, cadmium and other metals) occur naturally in the environment. Human activities can release these elements to the surrounding landscape. Natural deposits can also serve as sources of these elements. Regardless of their source, elevated concentrations of these contaminants can have adverse affects on biological resources.

A wide variety of chemical compounds are also used by society on a regular basis. These compounds can be released into the natural environment through spills, permitted discharges and other sources. While some chemical compounds are virtually non-toxic, others affect fish and wildlife when concentrations exceed a certain threshold. Thresholds of concern differ among contaminant types and (individual) organisms differ in their sensitivity to various contaminants. In addition, the length of time an individual is exposed often influences the degree of any adverse effect.

Some contaminants accumulate to a greater degree in predatory species. Concentrations of some contaminants magnify through food chains, with higher concentrations at the “top” of the food chain or food web.

The field of environmental toxicology continues to evolve at a rapid pace. New scientific studies are published every year, and with new research comes better understanding of how contaminants affect various species. Many factors are still poorly understood, for example little is known about the effects of chemical mixtures and the implications of long-term exposure to low levels of contaminants.

The U.S. Fish and Wildlife Service has been involved with studying the effects of environmental contaminants on fish and wildlife for several decades. As the main federal agency dedicated to protecting wildlife and their habitat from pollution’s harmful effects, the Service maintains an Environmental Contaminants Program with more than 75 offices around the country. The Service’s major responsibilities include the conservation of migratory birds, management of more than 500 national wildlife refuges, enhancement of fish and wildlife habitat, management and restoration of interjurisdictional fisheries, and recovery of endangered species.

Significant issues for the Environmental Contaminants Program in Alaska includes study of contaminants in the Arctic, study of contaminants in wildlife harvested for subsistence, evaluating the effects of contaminants in threatened, endangered and declining species, identification and cleanup of contaminants on National Wildlife Refuges, responding to oil and hazardous materials spills that affect trust resources, and restoration of species and their habitats injured by contaminant spills or releases.

Bald Eagle on whale carcass
Bald Eagle on whale carcass. Photo credit: USFWS.
Aleutian islands covered in cloudy mist
Aleutians - some contaminants are transported atmospherically. Photo credit: USFWS.

Contaminants in the Arctic

Northern regions of the world experience unique contaminants issues as a consequence of their location and climate. Long-range atmospheric transport and deposition in the Arctic occurs mainly in the winter when the low pressure drives much of the atmospheric circulation of the Northern Hemisphere. Airborne contaminants are drawn to high-latitudes from industrial areas in North America, Europe and Asia where, due to colder temperatures, the contaminants condense and precipitate out of the atmosphere. Once chemicals reach colder climates typical of high-latitudes, they are less likely to revolatilize as in warmer climates, and therefore persist in the environment and are incorporated in the food chain. International research programs such as the Arctic Monitoring and Assessment Programme (AMAP) have shown that long-range pollutant transport and accumulation are a circumpolar issue. Existing data also show, however, that atmospheric transport differs in various parts of the Arctic. It is therefore important to obtain specific information for Alaska since there is uncertainty in simply extrapolating results from other northern regions.

Localized sources of contamination also exist in Alaska and other northern areas, including old landfills, abandoned facilities, discarded drums and other point sources. These local sources can have a profound impact on fish and wildlife resources in the immediate vicinity.

Environmental Contaminants Program 

The Environmental Contaminants Program protects, improves and restores the quality of fish, wildlife and habitat resources in Alaska through the identification, prevention and resolution of environmental contaminant problems. We also provides technical assistance to various Service programs, other agencies and the public. 

For example:

  • We investigate environmental contaminant issues in species and habitats managed by the Service. In Alaska, these investigations include the study of contaminants in declining species, assessing the presence and effects of bioaccumulative compounds in predatory species, and evaluating contaminants in Service-managed species commonly used for subsistence. 
  • We provide technical support to the Endangered Species Program on contaminant issues that may affect listed species and their habitats, including the evaluation of proposed projects and the study of contaminant concentrations in these species. 
  • Environmental Contaminants Specialists provide technical comments on various federally-funded or federally- approved projects that could potentially affect trust resources by introducing contaminants into the environment or by posing a risk of contaminant spills.
  • As part of the Contaminant Assessment Process, we evaluate and summarize contaminant issues on each National Wildlife Refuge in Alaska. These refuge-scale assessments often lead to more detailed contaminant investigations and cleanup projects.
  • We work with the Environmental Compliance Program (Division of Engineering) and the National Wildlife Refuge System to plan environmental cleanups on refuge lands. We also provide technical support regarding contaminant remediation projects conducted by other responsible parties on Service-managed lands.
  • We work with refuges and other partners to implement an integrated pest management program on Service lands, and we evaluate proposed pesticide use on refuge land and in Service-funded projects. 
  • As part of our oil spill response program, we work proactively with partners to identify trust resources vulnerable to spills and to review spill response planning documents such as Area Plans and facility contingency plans. During major spill events the Service serves as an integral member of the Incident Command System, helping ensure that wildlife issues are addressed appropriately.
  • Following significant spill events and chemical releases, we work with others to restore injured natural resources.

Learn More About What We Do

Two FWS employees collecting soil samples near a creek.
Soil sampling. Photo credit: USFWS