Impact of accounting of 238U chemical toxicity on its permissible release level to atmosphere

At present, the permissible atmospheric release levels of ²³⁸U are evaluated only on a basis of its radiation impact on population. At the same time, uranium belongs to the 1^st hazard class (extremely dangerous chemicals) by its toxic effect. Limitation of the ²³⁸U release to the atmosphere is calculated separately using two criteria – radiation protection (annual dose limits) and chemical toxicity of uranium. It is shown that the permissible release level of 238U by radiation criteria is 100 – 250 times higher than the maximum release level limited by chemical toxicity of uranium. Annual intake limit of ²³⁸U for population 8400 Bq/year, established by Radiation Safety Norms NRB-99/2009, under condition of its uniform intake is equal to 184 mkg/kg of body mass per day for the indicated age group. It is 306 times higher than the tolerable daily intake of uranium estimated by World Health Organization. Compliance with the public health regulations in radiation safety does not guarantee that the annual intake of uranium by population would not exceed the tolerable toxicity levels indicated by World Health Organization. Therefore, the established value of the annual intake limit of ²³⁸U for the population needs to be revised taking into account the recent World Health Organization publications and the research results in the field of chemical toxicity of uranium. The revised value could be incorporated to the system of establishing the permissible atmospheric releases levels of radioactive substances.

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