Fisheries & Ecological Services
Alaska Region


Environmental Contaminants

Contaminants Overview

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. Bald eagle on carcass

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. USFWS. Click to Enlarge

Last reviewed: March 24, 2014