The Four New Groupings of ATH Substances - Substance-Specific Context Dioxins and Furans

Polychlorinated dibenzo-p-dioxins (PCDD or dioxins) and polychlorinated dibenzofurans (PCDF or furans) have been categorized as CEPA-toxic, persistent, bioaccumulative, anthropogenic and are now slated for virtual elimination (VE) under the Toxic Substances Management Policy (TSMP) adopted by the federal government in 1995. Dioxins and furans are listed on the UN/ECE Persistent Organic Pollutant (POP) Protocol as toxics with the potential for long-range transport through the atmosphere.

Typically, dioxins and furans are found in mixtures of 210 isomers, 17 of which are highly toxic (Schedule 1, Part 4, of the 2000 Canada Gazette notice (to obtain this document, please contact your NPRI regional office). The International Agency for Research on Cancer (IARC) has classified 2,3,7,8 tetrachlorodibenzo-para-dioxin as carcinogenic to humans and there is evidence to suggest that other dioxin-like compounds may also be carcinogenic. Dioxins are also associated with a variety of non-cancer effects in humans including endocrine disruption, immunotoxicity, developmental toxicity, dermal effects, cardiovascular disease and diabetes.

Dioxins/furans (DF)are unintended products of combustion and many industrial processes. They are environmental contaminants detectable in trace amounts in air, water and soil in virtually all parts of the global ecosystem. Once emitted, they can travel long distances far from the source and last for a long time. In the process, they accumulate in fatty tissue and increase in concentration as they move higher in the food chain. They are transferred in breast milk. More than 90% of the intake of dioxins and furans by humans is through food consumption. Dairy products, meat, fish and eggs are the primary sources of exposure. Ingestion of contaminated soil, inhalation of air and dermal adsorption are minor sources.

Anthropogenic Sources

Major Canadian sources that release into the air are:

• municipal solid waste,
• hazardous or medical waste,
• industrial incinerators,
• utility boilers.

They can occur as contaminants in the manufacture of chlorinated organic chemicals, in the production of cement, and in the metals smelting operations. Other activities that could lead to the releases of D/F include the combustion of hog fuel in the pulp and paper sector and the combustion of fuel in kraft liquor boilers. Smaller non-point sources include burning wood in stoves and fireplaces, landfill fires or open burning of garbage or agricultural lands. Natural sources of dioxins and furans include forest fires and volcanoes.

In Canada, during the last decade, atmospheric releases have been reduced by approximately 60%, due to facility closures or upgrades. The major success story is the upgrade of the Levis (Quebec) municipal waste incinerator, which resulted in bringing the largest single source of D/F to below the level of quantification, achieving virtual elimination from this source.

In regards to effluent releases, the pulp and paper industry was a major source of releases in the past. After implementing the D/F effluent regulations, this sector achieved virtual elimination of D/F in its effluent with a reduction of over 99%.

The CCME Development Committee for Dioxins and Furans has developed and finalized Canada-Wide Standards (CWSs) for two sectors:

• pulp and paper boilers burning salt-laden wood, and
• waste incineration.

The CWS for iron sintering has been accepted in principle by the CCME Ministers and they are now considering a CWS for steel manufacturing electric-arc furnaces. Other standards or approaches may be developed for other sectors that are known to release dioxins and furans.

To better refine the currently available data on dioxins and furans releases and to track progress toward the long-term goal of VE, it was requested that all facilities engaged in identified activities that have the potential to incidentally produce or release D/F or HCB report to the NPRI. Level of Quantification (LoQ) thresholds for releases to air, water and solids, against which progress towards VE will be gauged by, are listed below. LoQ is defined in the TSMP and in Section 65 of CEPA 1999 as "the lowest concentration that can be accurately measured using sensitive but routine sampling and analytical methods".

Due to the fact that dioxins and furans are often found in complex mixtures, at extremely low concentrations, it is difficult to determine their cumulative toxicity of the mixture. Accordingly, scientists have assigned toxic equivalent factors (TEFs) to each dioxin/furan congener as weighting factors. These TEFs are assigned relative to the toxicity of 2,3,7,8-tetrachlorodibenzo-para-dioxin, the most toxic congener, which is assigned a TEF of 1. TEFs are then used as weighting factors to calculated Toxicity Equivalents (TEQs), the units in which dioxins and furans are reported to the NPRI.

For a more detailed description of TEQs and their calculation, refer to section 5.4.4. of the Supplementary Guide for Reporting to the National Pollutant Release Inventory (to obtain this document, please contact your NPRI regional office).

Table: Estimated LoQ Values for Concentrations of Dioxins and Furans and HCB