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