Environmental Trends 2002

Chemicals in Wildlife

Average dioxin and furan levels in the digestive gland of Dungeness Crabs Near Pulp Mills

SOURCE: Pollution Prevention and Assessment Division, Environment Canada, Pacific and Yukon Region, 2001. NOTES: To approximate total risk from the most toxic chemical forms of dioxin and furans (17 of which are assessed in this analysis), all are assessed by comparing their toxicity to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), the most toxic of this group using an internationally accepted procedure. Concentrations derived in this manner are referred to as toxic equivalents (TEQs).

Trends in dioxins and furans in Dungeness crabs near pulp mills

• Between 1989 and 1998, average concentration of dioxin and furans in the digestive gland of Dungeness crab most highly exposed to pulp mill effluent decreased by 97%. Dungeness crabs are a good indicator of contaminant levels in sediment because they are bottom dwelling foragers that generally stay in the same area throughout their lifetime.

• In British Columbia, dioxins and furans were produced as a by-product of the chlorine bleaching process by pulp and paper mills. In the late 1980s, industries adopted technologies that minimize the release of dioxins and furans. The government introduced regulations in 1992 to motivate further reduction.

• A newly identified source of atmospheric dioxins and furans is the burning of wood that has been soaked in salt water. Government and industry are currently working together to find a solution to this issue.

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