POLYCHLORINATED-BIPHENYLS AND CHLORINATED PESTICIDES IN SOUTHERN ONTARIO, CANADA, GREEN FROGS

Green frogs were collected from seven southern Ontario, Canada, locati ons and analyzed for chlorinated organic chemicals to establish the re lative distribution of these chemicals at specific sites. At Hillman M arsh, a wildlife reserve in an agricultural area, green frogs accumula ted significantly greater amounts of highly chlorinated Polychlorinate d biphenyls (PCBs) than green frogs from all other collection sites. T he source of PCBs is unknown. At Ancaster, 1,1-dichloro-2,2-bis(p-chlo rophenyl)ethylene (DDE) accumulated in green frogs to a significantly greater extent than at all other sites. This was attributed to the pre sence of agriculture at Ancaster and the historic use of 1,1,1-trichlo ro-2.2-bis(p-chlorophenyl)ethane (DDT) in agriculture. Chemical concen trations measured in green frogs from all locations were considerably lower than reported levels in other species resulting in observable ef fects. Specific data relating chronic effects in amphibians to environ mental exposure to DDE and PCBs is lacking. Contaminant accumulation i n southern Ontario amphibians may be an important factor contributing to amphibian declines only at specific sites.