Environmental Trends 2002

Chemicals in Wildlife

Contaminants in Great Blue Heron Eggs (mg/kg)

SOURCE: Environment Canada, Canadian Wildlife Service, 2000. NOTES: Data are presented as geometric means of eggs sampled. Data for 1982, 1983, 1991, 1993, 1994, 1996, 1998 and 2000 are based on pooled samples. Data are from the Great Blue Heron colony at the University of British Columbia.

Status and trends in contaminants

• The level of some contaminants found in monitored wildlife species has been decreasing over the past 20 years. Since 1977, PCB levels detected in Great Blue Heron eggs at the University of British Columbia (UBC) colony have decreased by 85%.

• PCBs were banned from open uses in Canada in 1977, but PCBs are still present in electrical equipment manufactured before that date. Current levels of PCBs in wildlife are due to persistence and food chain cycling of these compounds, leakage from old landfill sites and atmospheric deposition from distant sources.

• Since 1977, levels of DDE, a breakdown product of the persistent pesticide DDT, decreased by 83% in Great Blue Heron eggs. Canada banned the use of DDT in the 1970s, but it persists in the environment and is still legally manufactured and used in some countries.

• Scientific information is accumulating on the toxic effects of organochlorines still in use. For example, PBDEs (polybrominated biphenyl ethers), a commonly used flame retardant found in office equipment, cars and aircraft, has similar chemical properties as PCBs and DDT and is increasing in concentration in the Canadian Arctic.

Why is it important?

• Human activities, including industry, transportation, waste disposal, agriculture, forestry and recreation have contaminated the environment with substances that are toxic to humans and other living organisms.

• One group of toxic substances, persistent organochlorines, includes pesticides, such as DDT, industrial compounds such as PCBs, and by-products of industrial processes and combustion, such as dioxins and furans. They are termed persistent because they linger in the environment for decades or even centuries before breaking down.

• These substances tend to accumulate within exposed organisms (bioaccumulation) and increase in concentration as they rise through the food chain (biomagnification).

What is being done?

• Measures designed to minimize or eliminate exposure to contaminants include: stringent regulations for the management of toxic wastes; the use of pollution prevention planning; industry initiatives; and a program for responsible management of household hazardous waste.

• Pollution prevention planning encourages industry to reduce hazardous waste during the production process.

For detailed information, including graph data, see In-Depth report [pdf].