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A Decade of Research on the Environmental Impacts of Pulp and Paper Mill Effluents in Canada (1992-2002)

5.5 AOX: Regulation and relationship to effects

As part of its regulatory program initiative, in order to determine what to do with organochlorine discharges under its legislation, the federal government conducted an assessment of effluents from mills using bleaching under the Canadian Environmental Protection Act (CEPA) in the mid 1990s. This was done to determine whether the effluents met the criteria for CEPA toxicity designation and to define how the releases should be addressed. The assessment concluded that the effluent met the toxicity criteria used under CEPA. However, the assessment also observed that the quality of the underlying science was insufficient to design regulations curtailing organochlorine discharges beyond what would be attained with the proposed dioxin-furan measures and the new FA regulations. Information deficiencies noted included knowledge of the make up of the organochlorine, since chlorine was present in a broad array of organic compounds with molecular weights from around 50 to multi thousands. Adding to this little was known about which compounds were responsible for the observed environmental effects.

In 1992, the Province of British Columbia modified the Pulp and Paper Mill Liquid Effluent Control Regulation (PMLECR) to require that the discharge of AOX from bleach plants be eliminated by the 31st of December, 2002 . In December, 2001, the Minister of Water, Land and Air Protection, appointed a Scientific Advisory Panel to review the scientific basis of this requirement (Carey et al., 2002). The panel did not find evidence that the present level of AOX discharges from British Columbia 's bleached kraft mills, and its one ammonia based sulphite mill, present a demonstrable risk to the ambient aquatic environment that could be attributed to AOX (Figure 5). The panel concluded that there was no evidence available to it at this time to indicate that further reductions of effluent AOX beyond that already achieved would result in any demonstrable environmental benefit. These findings were also supported by industry studies which found that AOX was not a good predictor of acute or chronic toxicity (O'Connor et al., 1993). While the panel concludes that the elimination of AOX is not a high priority as an environmental goal, it also concludes that it would be desirable to limit AOX discharges to levels comparable to those currently being discharged by the BC mills. Such a limit would make BC regulations comparable to those in most other pulp producing jurisdictions, and would ensure that the benefits achieved in recent years relating to reduced contamination of aquatic resources by pulp mill-related organochlorines are not lost.