Dioxins are unwanted by-products produced by both industrial processes and natural events, such as forest fires and incomplete combustion. Levels of dioxins in the Canadian environment have decreased significantly over the last several years.

According to Environment Canada's Draft Second Edition June 2000 report, "Dioxins and Furans and Hexachlorobenzene Inventory"¹, emissions of dioxins to air, water and soil have decreased from an estimated 1,043 grams/year TEQ in 1990 to an estimated 378 grams/year TEQ in 1999 - a reduction of 64%. The inventory is available on line at Environment Canada's website http://www.ec.gc.ca.

To ensure further reductions, a multistakeholder process is currently underway to develop Canada-Wide Standards for emissions of dioxins/furans. In June 2000, the Canadian Council of Ministers of the Environment proposed a new Canada-wide standard for incinerators to 0.08 nanograms/cubic metre by 2006.

The top sources of dioxin emissions to air listed in the above inventory¹ are:

• Conical Burners - 75 grams/year TEQ
• Waste Incineration - 41 grams/year TEQ
  • Medical - 25 grams/year TEQ
  • Municipal - 9 grams/year TEQ
  • Hazardous - 7 grams/year TEQ
• Residential wood combustion - 19 grams/year TEQ
• Steel Manufacturing - Electric Arc Furnaces- 14 grams/year TEQ
• Pulp & Paper- Burning salt-laden wood - 8 grams/year TEQ
• Iron Manufacturing - Sintering Plants - 6 grams/year TEQ

Several studies have shown there is no significant relationship between the amount of chlorine in incinerator feeds and the dioxin emissions from waste incinerators - it is an issue of combustion efficiency. Better combustion practices, having the Best Available Techniques installed on incinerators, have the biggest effect on further reducing dioxin emissions.²

1. The inventory is available on line at Environment Canada's website http://www.ec.gc.ca.

2. American Society of Mechanical Engineers. 1995. The Relationship Between Chlorine in the Waste Streams and Dioxin Emissions from Waste Combustor Stacks. CRTD Vol. 36.
Wikstrom, E., Marklund, S. 1998. The influence of level and chlorine source on the formation of PCDD and PCDF during MSW combustion. Organohalogen Compounds 36: 347.
Yennie, C.R. 1997. Methods to Reduce HCl Emissions in a Medical Waste Incinerator Equipped with a Dry Scrubber. Presentation at the Air & Waste Management Association's 90th Annual Meeting & Exhibition, June 8-13, 1997.
Visalli, J.R. 1987. A Comparison of Dioxin, Furan and Combustion Gas Data from Test Programs at Three MSW Incinerators. Haz. Waste Mang. 37: 1451-1463.