Regulations introduced to pulp mills along Howe Sound have eliminated new input of marine pollutants associated with the industry. Yet lingering concentrations in marine sediment and Dungeness crab underscore the persistent impact of these toxins, so concerns remain.
Author: Juan Jose Alava, Institute for the Oceans and Fisheries, The University of British Columbia and Ocean Pollution Research Program, Coastal Ocean Research Institute
Reviewer: Marie Noel, Research Manager, Ocean Pollution Research Program, Coastal Ocean Research Institute
Banner Photo Credit: Bob Turner
Historically, two pulp mills have long operated in Howe Sound, the Port Mellon and the Woodfibre mills. The Howe Sound Pulp and Paper (HSPP) mill at Port Mellon began operation in 1908 and is the only mill in operation today in Howe Sound. For decades, effluent from HSPP and the Woodfibre mill, which closed in 2006, created a variety of impacts on receiving waters in Howe Sound. These impacts included high biological oxygen demand causing oxygen depletion, smothering of local seafloors with fine fibre beds, reduced light penetration leading to lower phytoplankton production, and impacts from a variety of chemical contaminants, including dioxins and furans. The chemical contamination resulted in the closure of fisheries in most of Howe Sound in the 1980s. However, effluent regulations introduced in the late 1980s and early 1990s and mill process changes since the mid-1980s have dramatically reduced contamination and related impacts in Howe Sound.
In 1995, harvest restrictions due to dioxin/furan contamination were removed for 40 percent (486 square kilometres) of the previously closed area in Howe Sound, and today permanent fisheries closures remain in effect for crab but not for prawn, shrimp and finfish. Recent sampling reveals that dioxins and furans remain in the sediment in the proximity of HSPP, but levels in sediments are generally decreasing. Contamination in fish and shellfish has generally declined near HSPP to levels below the Health Canada consumption criteria, but advisories to limit consumption of crab (i.e., specifically the hepatopancreas where dioxins are concentrated) are posted and remain in effect in Howe Sound. Environment Canada oversees an Environmental Effects Monitoring (EEM) program that continues today at the HSPP mill.
Why is it important?
For many years, the Port Mellon (i.e. HSPP) and Woodfibre pulp mills used liquid chlorine for the bleaching process and, consequently, produced and discharged effluent containing byproducts known as polychlorinated dibenzo-p-dioxins (i.e. dioxins) and dibenzofurans (i.e. furans). Human intake of dioxins and furans poses potential health risks because these organic pollutants are among the most persistent, toxic, bioaccumulative and carcinogenic hazards to humans. Because of dioxin and furan contamination in the marine environment and high tissue concentrations in seafood, fisheries (including harvesting of prawn, shrimps and crab) were closed in Howe Sound and other parts of the B.C. coast near pulp mills in 1988.
What is the current status?
Monitoring has shown a marked decrease in dioxin and furan contamination in Howe Sound over time (Figure 1).
However, in 2012, dioxin and furan concentrations in the hepatopancreas of Dungeness crab collected from three of eight sampling sites at the HSPP mill exceeded the Health Canada consumption criteria, indicating that crabs from these sites are not safe or suitable for human consumption.
Contamination in sediments decreased by 19 percent at Port Mellon and 99 percent at Woodfibre between 1987 and 1995 (Figure 1, bottom panel). The more rapid decrease of dioxins and furans at the Woodfibre mill site relative to Port Mellon likely relates to higher rates of fresh sediment deposition at the Woodfibre site due to its proximity to the mouth of the Squamish River. In 2012, concentrations of dioxins and furans in sediments near the Port Mellon mill were still within the lower end of the historical range, suggesting that the sediments here may act as both sink and source of dioxin and furans.
At the Woodfibre pulp mill, effluents were treated with an oxygen-activated sludge system starting in December 1992, resulting in a 95 percent reduction in biochemical oxygen demand, meaning that the effluent no longer used up oxygen that plants and animals need to survive in the receiving marine water. Monitoring of fish tissue at Woodfibre up until the time of mill closure in 2006 indicates decreasing concentrations of dioxins and furans. However, dioxin and furan concentrations in 2006 in crab hepatopancreas and dogfish liver near Woodfibre remained above the Health Canada consumption advisory threshold.
While the level of dioxin and furan contamination has decreased in the region, ongoing monitoring is still required as the most recent data showed that Dungeness crabs still have elevated levels of dioxins in some locations at the HSPP mill. Seafloor sediments can function as a contaminant source or sink because exposure pathways for crabs may have changed since the mills ceased producing dioxins and furans; sediment contamination may have improved faster at some sites than others.
What can you do?
Individual and Organization Actions:
- Avoid the incineration of organic matter and plastics to prevent the release of dioxins into the air and coastal environment.
- Use and apply “green” or homemade pesticides and organic fertilizers in gardens and agricultural fields to avoid toxic run off (e.g., salmon friendly lawn and/or orca friendly lawn: non-toxic pesticides, non-toxic herbicides, non-toxic fertilizers).
Government Actions and Policy:
- Help to guide and design creative solution-oriented practices to reduce the levels of dioxins and furans in Dungeness crabs which still exhibit concentrations of dioxin/furans of concern for public health.
- Promote and sponsor national programs and solutions for marine pollution to protect ocean life from human made chemicals with research, continued education and engagement, and advocacy to succeed with actions.
- Continue with the implementation of source controls and regulations to hamper dioxin and furan pollution from pulp mills in the coastal marine environment of Howe Sound.
- Regulate and control the usage of pesticides containing potential traces of dioxins and furans as impurities to avoid the accidental release of these byproducts into the coastal marine environment.
- Address the appropriate disposal of old tanks and bins and any material containing dioxin-contaminated fluids and/or oil from former military facilities, old refineries, junk yards and harbours.