222Radon carcinogenesis: Risk estimation in different working environments

Background: Occupational exposure to radon in working environments should be considered as chronic because the subjects involved undergo the effect due to the ionizing radiation from the same gas and decay products. The exposure characteristics create conditions for toxicological, radio-toxicological cellular, subcellular, and molecular mechanisms that lead to lung cancer. Aim: Our aim is to clarify the prediction of probable cases of lung cancer in 222Radon-exposed subjects in order to point out an obvious risk that should not be underestimated, particularly in subjects with an accumulated dose in many years of activity and for the previously underestimated gamma radiation (214Bi). Materials and Methods: A total of 168 electret sensors were set in couples for 84 surveys in working environments; also a further pair of them was used in order to determine the background γ generated by cosmic rays and we considered four group: general population, never smokers, former smokers, and current smokers. Results: Results are expressed in terms of mean and standard deviation, standard error, geometric mean with statistical significance (P < 0.01 [t-test]), and excess lifetime cancer risk (ELCR). They demonstrate an increase of both mean concentrations (P < 0.01 [t-test]) and ELCR. This happens with multiple values of the allowed limits >150 Bq m3 (U.S. Environmental Protection Agency, EPA) or >300 Bq m3 (international commission radiation protection), until to an individual accumulated dose as 90–95 work level month. We have detected the environmental variability associated with the structural characteristics of the buildings and their construction. Conclusion: The results showed that exposure in underground environments is significant although generally these environments are used as archives. Surprisingly, data greater than expected are also evident on the ground floor and first floor of historic buildings with solid and compact walls, with other factors playing a role as reduced or absent air changes during the night and activation of heating when work is resumed after renovation.