• Polychlorinated biphenyls;
  • Pesticides;
  • Amphibian declines;
  • Southern Ontario


Green frogs were collected from seven southern Ontario, Canada, locations and analyzed for chlorinated organicchemicals to establish the relative distribution of these chemicals at specific sites. At Hillman Marsh, a wildlife reserve in an agricultural area, green frogs accumulated significantly greater amounts of highly chlorinated Polychlorinated biphenyls (PCBs) than green frogs from all other collection sites. The source of PCBs is unknown. At Ancaster, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) accumulated in green frogs to a significantly greater extent than at all other sites. This was attributed to the presence of agriculture at Ancaster and the historic use of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in agriculture. Chemical concentrations measured in green frogs from all locations were considerably lower than reported levels in other species resulting in observable effects. Specific data relating chronic effects in amphibians to environmental exposure to DDE and PCBs is lacking. Contaminant accumulation in southern Ontario amphibians may be an important factor contributing to amphibian declines only at specific sites.