Uranium Toxicity
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Uranium presents both chemical and radiological hazards. Risk assessments must address both types of hazards, therefore.
Unfortunately, there are some problems with the comparison of these hazards:
- insufficient data for chemical toxicity:
there is no data available for long-term effects of uranium ingestion
on humans, all information available is from intermediate-term studies
on animals,
- standards for radiation doses and chemical toxicity not comparable:
for
radiation and for cancer-inducing effects of chemical toxics, a linear
dose-effect relationship is assumed at low doses and low dose rates;
therefore any standard can only limit the effects to a selected level,
while for non-cancer-inducing effects of chemical toxics, the existence
of a no-adverse-effect level is assumed.
- residual risk from chemical toxicity regarded acceptable usually is orders of magnitude lower than from radiation:
the lifetime cancer risk from continuous radiation exposure at ICRP's
dose rate standard for the public of 1 mSv/a during a 70 year lifetime
is 1 : 286, and the lifetime cancer risk for workers exposed at ICRP's
current dose rate standard for workers of 20 mSv/a during a 40 year
work life is 1 : 31, while the acceptable lifetime risk from toxics
often is selected in the 1 : 10,000 to 1 : 1,000,000 range.