The potential impact of environmental pollutants on human health can be evaluated by laboratory analysis of environmental samples or by measurement of biological effects on indigenous populations and/or specific test organisms placed in the environment to be monitored. The organisms most commonly used to assess mutagenicity under real world conditions are flowering plants, wild and captive mammals, and aquatic vertebrates. Plant species have been used to monitor ambient air quality around several major industrial cities in the USA, nuclear power plants, and industrial waste sites, and also to assess potential health effects of municipal sewage sludges. Domestic animals can be used as sentinels to provide information on effects of contaminants in the environment and have been used to a limited extent to evaluate environmental influences on the occurrence of breast cancer and osteosarcoma. Cytogenetic analysis from feral and wild animals has been employed to assess health hazards and prioritize clean-up efforts at hazardous waste sites. Aquatic animals have been used more often than terrestrial animals or plants to identify and characterize the genotoxic effects of environmental pollution.