§ Mr. Sayeed
To ask the Secretary of State for Environment, Food and Rural Affairs, pursuant to her answer of 12 November 2001,Official Report, column 598W, on dioxins, what assessment she has made of where the dioxins emitted to air from an incinerator end up and how long they are likely to remain in the environment. 1356W
§ Mr. Meacher
Low levels of dioxins can be detected in all environmental media and, in the UK, the mean levels are currently approximately:
- Air (ambient rural)—10 femtograms per cubic metre
- Air (ambient urban)—100 femtograms per cubic metre
- Soil (rural)—5 nanograms per kilogram
- Soil (urban)—30 nanograms per kilogram
- River sediments—20 nanograms per kilogram.
The critical factor for all of these is the concentration in air, which itself is controlled by emissions from primary sources and by complex exchanges/recycling of dioxins with water, soil and vegetation. Dioxin emissions to air from municipal solid waste incinerators contribute less than 1 per cent. of total dioxin emissions, so they currently make only a minor contribution to environmental concentrations.
Dioxins are persistent in the environment and commonly have half-lives in soils and sediments in the order of years, although these will vary between the different compounds and media.