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     ... challenging the spin 

                             Site Revised September 10, 2007


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Acute Dioxin Exposure

Although TCDD is a very lethal compound, there has never been a fatality due to acute TCDD exposure.

A number of laboratory experiments have measured the effects of acute dioxin exposure (short term, high levels).  One researcher found that TCDD was lethal to one species of rat (LDLO) at an exposure level of 5 micrograms (microgram= a millionth of a gram) per kilogram of animal body weight. 

To put this into context, strychnine, a very poisonous alkaloid is lethal to rats at 500 microgram per kilogram of animal body weight.  Polytoxin, the most poisonous non-protein substance known is lethal to mice at 0.45 microgram per kilogram of body weight.

On an acute exposure basis, TCDD is more lethal than strychnine but less toxic that polytoxin.  There is one additional difference: strychnine and poyltoxin kill very quickly, TCDD may have several days before being lethal to laboratory animals.

If we assume that 1000 ppt TEQ is really equivalent to 1000 ppt TCDD (it's not), a  man, that weighs approximately 70 kilograms (154 lbs), would need to consume approximately 805 pounds of floodplain soils contaminated with 1000 ppt TEQ dioxins to ingest a lethal dose of equivalent TCDD.

A Dow Midland plant employee would need to consume approximately 45 pounds of soil from the vicinity of the old Strong Phenol pond (TEQ level ~ 18,000ppt) in order to ingest a lethal dose of equivalent TCDD.

Neither of these two soil ingestion requirements seem very likely.

The exposure risks from dioxins and furans is not related to acute toxicity... the primary health risk is from chronic, long term exposure at much lower levels.

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