[en] It can be stated with confidence that there are a number of factors involved in the etiology of cancer, genotoxic ''pollution'' being one of them. Ionizing radiation is one of the factors involved, but the important role played by various chemical products must not be forgotten. Ethylene oxide (EO) is particularly noteworthy in this connection as an alkylating agent, a mutagen and probably also a carcinogen. This gas is used very widely in the chemical industry and also in cold sterilization and disinfection processes. Measurements of the atmospheric concentration of EO have been carried out systematically over short or long periods in four sterilization plants of different capacities. A work study was conducted on 27 persons exposed to the gas every day. In conjunction with atmospheric data and the rad-equivalence principle, the information obtained from the study was used to evaluate their annual occupational exposure, the level of which proved to be high. Biological surveillance of the subjects exposed offers a possible method of checking this evaluation and of monitoring personnel. The alkylation rate of various haemoglobin amino acids can be measured in this way, but here difficulties arise in collecting the necessary blood samples. (author)