Risk assessment due to inhalation of radon decay product aerosols

Risk assessment due to inhalation of radon decay product aerosols 

Nero (1988) has pointed out, such a high level of risk greatly exceeds those normally associated with environmental hazards. 

The radon concentration indoors in terms of radiation dose exposure is expressed in WL (Working Level, the radiation level of 100 pCi per litre or 3700 Bq per m of Rn in equilibrium with its decay products). Effects of radon are given in terms of WLM (Working Level Months), which is the exposure at 1 WL for one working month, or 170 h. Since there are 365 X 24 = 8760 h per year and 80% of them (7000 h) are spent indoors, the annual time of exposure is 7000/170 = 41 working months . A world-wide representative value adopted by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 1977) is that 1 pCi per litre or 37 Bq per m is the average Rn concentration indoors, with an equilibrium factor (ratio of Rn decay product concentration to their concentration in radioactive decay equilibrium with Rn gas) of 0.5. This corresponds to an average concentration of 0.005 WL or 5 mWL. The annual indoor exposure is then 0.005 WL x 41 WM = 0.205 WLM. 

Albert, R.E., Arnett, L.C. (1955). Oearanceof radioactive dust from the lung. Am. Med. Assoc. Arch. Ind. Health 12, 

Albert, R.E., Petrow, H.G., Salam, A.S., Spiegelman, J.R. (1964). Fabrication of monodisperse Incite and iron oxide particles with a spinning disk generator. Health Phys. 10,933. 

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