Synergistic effects are toxic effects caused by a combination of chemicals that produce total toxic effects that are greater than the effects of the sum of the effects of the individual chemicals. In effect, synergism is like one plus one equalling three or more.

The study of synergistic effects is important to government regulators and scientists who are working to establish standards that set legally-permissible levels for air, water, and ground pollution. For example, current air and water quality standards set by the United States Environmental Protection Agency (EPA) are based on studies of single metals and chemicals and how each affects plant, animal, and human life. Pollutants from a single factory could meet the EPA's air or water quality standards and still harm plant, animal, or human life because of synergist interactions among the chemicals in the substances being discharged. Environmentalists believe that air and...