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What is Happening?Dioxin and furan levels in the hepatopancreas (digestive gland) of Dungeness crab collected near nine British Columbia coastal mill outfall sites have dropped an average of 92%. Contaminant levels have gone from an average of 735 picograms per gram (pg/g) in 1989 to 24.5 pg/g in 2003. Since 1996, the average levels in crab hepatopancreas have remained near or below the original 30 pg/g guideline level for tolerable daily intake. Similarly dioxin and furan contamination in sediments collected near these coastal pulp mills dropped from an average of 252 pg/g in 1990 to 36.8 pg/g in 2003. Improvement at the nine different outfall sites ranged from 59% to 97% with an overall average improvement of 76%.
Source: Environmental Protection Branch, Environment Canada, Pacific and Yukon Region, 2005. Note: to approximate total risk from the most toxic chemical forms of dioxins and furans (17 of which are assessed in the 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). Note also that the number of mills in operation has varied during the time period. From 1999 to 2003 monitoring was confined to five mills (Crofton, Elk Falls, Port Mellon, Squamish and Skeena in Prince Rupert). The Dungeness crab is a good environmental indicator of toxic contaminants because it bioaccumulates contaminants in its tissue especially from the consumption of food containing the contaminants. It stores these contaminants in the fat-rich digestive gland (hepatopancreas). It bioconcentrates contaminants at a higher level than finfish and many other shellfish (e.g. shrimp), partly because of its relatively sedentary nature and because it favours sandy substrates where contaminated sediments often accumulate. The Dungeness crab is also a useful indicator species due to its importance to commercial, recreational and First Nations harvests.
There are differences in levels of dioxins and furans for crab and sediment between mill outfall sites. Outfalls located on the open coast show a less dramatic decrease in contaminants. These sites (4 mills) have high-energy environments with sediments often mixed by strong waves and currents, or even by burrowing marine organisms. This often keeps "old" contaminants at or near the surface and exposing organisms that live and feed on this surface. Sediment dioxin and furan levels from some of these open coast sites have been highly varaible since 1993. The other mills are located on fjord sites and show a faster contaminant recovery likely due to high clean sediment input from discharging river systems. Other processes such as bioturbation, or the biological mixing of sediments, rate of sediment burial and sediment chemistry can affect this difference in contaminant levels between crab and sediment at each location along the coast. Why is it Happening?Nine pulp and paper mills (location map) discharge secondary-treated effluent to the marine waters of British Columbia. Initial monitoring from 1987 to 1989 documented elevated dioxin and furan levels in edible fish and shellfish collected from sites near nine of these mills. The federal government responded by issuing harvesting restrictions on various crab, clam, prawn, shrimp, and oyster fisheries, requiring mills to conduct annual monitoring and introducing legislation to control dioxin and furan discharges. Before the regulations were promulgated, the B.C. pulp and paper mills implemented a major capital investment that changed their processes to improve the effluent quality and reduce the loading of dioxins and furans to the marine environment. This is reflected in the trend in dioxin and furan loadings from the mill's effluent measured since 1989.
Source: Environmental Protection Branch, Environment Canada, Pacific and Yukon Region, 2005. Cautionary note: Since 1997, all coastal mills now sample their effluent annually (rather than monthly or quarterly as in previous years) to comply with the Pulp and Paper Mill Chlorinated Dioxin and Furan Regulations. This is because of significant reductions in dioxin loadings and many reports of non-detectable levels of 2,3,7,8-TCDD and 2,3,7,8-TCDF in the effluents of coastal mills. For more details on the mills and their loadings rates see Graph Data. The total loading of dioxins from the BC coastal pulp and paper mills was estimated at 50.9 mg/d in 1989. By 1996, loadings were reduced to less than 2.5 mg/d, a 95% reduction. Similarly loading levels for furans have decreased by approximately 99% during the same period. In 1999, all mills reported non-detectable 2,3,7,8-TCDD in their effluent. For that year 1/2 the 2 pg/L detection limit was used and a total dioxin loading of 1.01 mg/d was estimated. Similarly from 2000 to 2003 all mills reported non-detectable 2,3,7,8-TCDD in their effluent and a total dioxin loading of 1.00 mg/d was estimated. More information is available in Environment Canada's inspection and compliance reports. Why is it Significant?Dioxins and furans are contaminants of serious concern as they have the potential to cause effects even in extremely minute quantities. For instance, in a 56 day laboratory experiment rainbow trout mortality occurred at concentrations of dioxin (2,3,7,8-TCDD) as low as 40 parts per quadrillion (Mehrle et al. 1988) - a part per quadrillion is equivalent to one cent in 10 trillion dollars. These compounds are highly persistent, with a high potential for accumulating in living tissue as seen in the Dungeness crab. In the studies of people exposed to chemicals contaminated with dioxins and furans, some displayed adverse effects on their skin (such as chloracne), liver, immune system, their senses or behaviour. No conclusive link has been established between human exposure to dioxins and furans and cancer. For more details consult Health Canada. However, because of the potential of fish and shellfish to bioaccumulate contaminants, certain consumer groups who eat large amounts of seafood may be at risk. Consequently, initial monitoring conducted in 1987 and 1988 resulted in the Department of Fisheries and Oceans (DFO) implementing the first dioxin-mediated shellfish closures in November 1988. Subsequent, expanded monitoring resulted in additional areas being subjected to harvesting restrictions. By February 1995, a maximum of nearly 1200 km² of B.C. coastal waters were affected by dioxin/furan-related harvest restrictions (consult DFO's Tidal Waters Sport Fishing Guide for specific information on areas closed).
Source: W. Knapp, Department of Fisheries and Oceans, Vancouver, 2001. The closure areas are for crab at eight coastal pulp and paper mill locations. The dates when harvesting restrictions were placed and lifted are shown on the graph. Dungeness crab contribute importantly to the commercial, recreational and First Nations harvests. In terms of the commercial fishery, coast-wide landings of Dungeness crabs peaked in 1993 at nearly 6300 tonnes but declined to just under 5000 tonnes in 1996. Despite the reduced landings, the annual landed value of crabs remains high as markets continue to develop. The total landed value of Dungeness crabs increased from over $18 million in 1993 to $23 million in 1996 and the Dungeness crab fishery ranks second in landed value of invertebrate fisheries in the Pacific Region (DFO-Pacific Region, 1998 Crab Management Plan). Although the above mentioned closures have affected the fishery for this species, the full extent of this is unknown. As a result of abatement activities already initiated by the mills, dioxin and furan in effluent became virtually undetectable and contaminant levels in biota similarly showed a rapid decline. This led initially to dioxin/furan-related fisheries restrictions being lifted for shrimp, prawn and oysters in February 1995 and for some crab harvests in August 1995, April 1996 and September 1997. Over 550 km² or 46% of the maximum area closed in February 1995 have now had their harvest restrictions lifted. What is Being Done?Following the initial data collection from 1987 to 1989 of biota and sediments near B.C. coastal mills, a Dioxin and Furan Trend Monitoring Program was prescribed in 1990 by the federal government, under the Canadian Environmental Protection Act (CEPA). Sampling programs are specified annually by DOE following consultation with DFO. The participating mills are responsible for collection and analysis of the data. The results are submitted to DOE and DFO for evaluation and then referred to Health Canada (HC) for a human health hazard assessment. Based on advice received from HC, DFO makes decisions regarding fish harvest restrictions. During 1987 - 1992, the pulp and paper industry implemented major capital investments and operational changes to the mills including the use of uncontaminated wood chips and defoamers, new pulp bleaching and washing practices, oxygen-based pulp cooking, and the installation of new treatment works. In 1992, the Pulp and Paper Mill Effluent Chlorinated Dioxins and Furans Regulations were introduced under the Canadian Environmental Protection Act (CEPA). The regulations required that all mills using chlorine bleaching process achieve the maximum discharge limit in the final effluent of 15 parts per quadrillion (ppq) for dioxin (2,3,7,8-TCDD) and 50 ppq for furan (2,3,7,8-TCDF) by January 1, 1994. Mill operators are also required to sample the final effluent according to regulations and to report the results to Environment Canada within 60 days of sample collection. Environment Canada does inspections of these sites and reviews company submitted monitoring data for compliance to the regulations. For more details on the inspections and compliance activities of Environment Canada consult the Inspection Division web site.
For more information contact: Bob More of DOE about dioxin/furan monitoring issues or Wayne Knapp of DFO for fisheries closures issues. Check the following sites for additional information on this indicator:
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