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Assessing the dioxins risk

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With reference to the article on dioxins (AJ 10.1.02), readers should be aware that dioxins sublime at ambient temperature.

Were any studies done on the ash pile by putting the inert material containing ash in a sealed chamber, and analysing the air and surfaces of the chamber after some time? A building constructed with this material may possibly build up dioxins in the air, producing long-term low-level exposure to occupants.

The use in road substrates is more benign since it is not confined to a closed space.

Also, the dioxins which sublime are exposed to ambient sunlight, a source of ultraviolet radiation, where they are destroyed. The highest risk would be to the workers handling the ash. At the very least, these workers should wear protective equipment, and shower immediately after.

Handling the ash may create dust, which may put persons at risk from inhalation. An environmental impact study should be initiated to assess the dangers.

The dioxins (if any) in the ash are almost certainly not the source of illness from exposure to the ash. At rather high exposure levels, the only acute effect is a skin rash called chloracne. It resembles juvenile acne and it is highly unlikely that the ash has levels this high unless chlorinated chemicals were burned.

The health dangers from low-level exposure to dioxins are an increased risk for contracting cancer, immune system suppression, and birth defects (teratogenicity) if women are exposed at a specific time during pregnancy.

The quoted value of 0.01 per cent dioxin content of the ash pile, is huge, regardless of how it is expressed (weight or volume per cent). In the US, levels are regulated at the part per trillion level (1:0.00000000000X).

Are you sure that the quote is accurate?

This comparison of bonfire dioxins and those in an ash pile is specious. All bonfires disperse dioxins in the smoke over wide areas, diluting the dioxin content and any consequent exposure. The dioxins in the ash pile however, are concentrated in one small area, making them potentially more dangerous (depending on the levels). If that ash pile contains some significant fraction of the dioxins produced by all the bonfires in the country, then the ash pile poses a significant risk.

Lewis A Shadoff, PhD, Brazosport College, Texas Austin Williams writes: Many thanks to Mr Shadoff, who makes some valid points in relation to the case, although it seems to be riven with contradictory levels of reason and caution.We start with a question on whether the dioxins have been tested (answer: yes, but only ill-defined samples were sent to a reputable independent company) and although the results were individually high, 'no generalised conclusions could be drawn'. However, Shadoff is still prepared to presuppose that building products made with this material, may produce long-term, low-level exposure. Based on his premise, he goes on to advise that workers should shower after contact! This can only be a precautionary approach to the matter, rather than an analytical one. On one hand he states that high levels produce only chloracne but then goes on to conclude that low levels cause cancer. It's all a question of levels.

The Environment Agency was quoted in the programme as saying that dioxins levels in the Dagenham ash pile were 'at least 1,000 times lower than the threshold which would classify the ash as hazardous or special waste'. They added that, therefore, 'dioxins would have had to constitute 0.01 per cent of the total content of the Dagenham ash pile' to be dangerous. This shouldn't be mathematically contentious.

I am all in favour of more research, but let's do it with an open mind and judge consequences on the basis of established scientific results.

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