Monday, September 13, 2004
More dioxin fallout
Just a quick update on the unfolding Taranaki dioxin story:
A frame of reference:
The Ministry of Health has produced a document that outlines the where the levels of dioxin found in the Taranaki residents fit in the scheme of other studies. The average level in the report was 11pg/g lipid (11 picograms per gram of lipid -a picogram is one trillionth of a gram.) The average in New Zealand is near to 3 pg/g lipid, Americans have on average 5 pg/g lipid. In another New Zealand study people that sprayed the herbicide 2,4,5T for a living had on average something like 50pg/g lipid and workers exposed to TCDD in the manufacture of Agent Orange have a staggering 2000pc/g lipid TCDD on average. Members of the Agent Orange study have a higher rate of cancer than their national average. The level shown in the Taranaki report is similar to the average TCDD level found in areas of Vietnam that where sprayed with Agent Orange.
What about the workers?
Given that the worst exposure to dioxins measured in international studies is found in people that actually worked producing chemicals shouldn’t there be some concern for Ivan Watkins-Dow’s former employees? Massey University epidemiologist Neil Pearce thinks so and has said as much to a New Zealand Herald reporter.
Greenpeace get it “plain wrong”
Greenpeace is an organisation that really worries me. I agree in principle with most of the things that they stand for but really don’t think they go about things the right way. This press release is another example of that:
“The report released yesterday by the Ministry of Health confirms that the levels of dioxins in Paritutu residents are much greater than the safe tolerable daily intake of dioxins identified by the World Health Organisation(WHO)”No, it doesn’t. The report itself doesn’t mention anything about the levels of exposure that residents where subjected to on a per day basis – it only sows the level of dioxin in the blood now. Another document (PDF) produced as an appendix to the report by Air and Environmental Sciences does estimate the by day exposure to dioxins. This document explains how soil concentrations of TCDD at various depths were used to estimate the concentration of TCDD in the air and soil in the past. Unfortunately this kind of modelling is very imprecise and since three different models were applied the only results that could be produced were a range of possible exposures. The report actually says that exposure to TCDD could be anywhere between 1pg/kg body weigh (well within the WHO Tolerable Daily Intake) to as much as 80pg/kg for a woman aged over 50 who had breathed air in the effected area 24/7 during the time of effect and had a diet where 10% of the fruit, vegetables and poultry she ate were produced in the effected area. Probabably an unlikely scenario. 80pg/kg body weight is 20 times greater than the WHO Tolerable Daily Intake. There is no sensible scientific method by which to favour one estimate over another which makes Greenpeace’s claims unfounded and unhelpful.
1 Comments:
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