Bromoethene. Documentation of permissible occupational exposure values

Bromoethene (vinyl bromide, VB) is a colourless, flammable gas with a characteristic pungent odour. It is used as a transient compound in organic synthesis, and also in the production of polymers, copolymers, flame retardants, pharmaceutics and fumigants. Occupational exposure to bromoethene may occur in production processes, processing and finishing. Because of its low boiling point (15.8°C), bromoethene has the form of a gas in the occupational environment, and thus inhalation is the major route of exposure. In Poland, 100 workers involved in organic and polymer syntheses, as well as in the manufacturing of pharmaceutics and fumigants are exposed to this compound. In the available literature, there are no data concerning toxic effects of bromoethene in humans. In laboratory animals, high concentrations of bromoethene have an acute hepatoxic effect and a depressant effect on the central nervous system. It has been reported that chronic exposure of rats to a low concentration of 44 mg/m3 (10 ppm) induces hemangiosarcoma of the liver. Bromoethene is an analogue of vinyl chloride, a well documented human carcinogen. The carcinogenic effect of bromoethene is generated by its metabolism to 2-bromoethylene oxide that produces cyclic etheno adducts with DNA. Toxicokinetic data show that the carcinogenic potential of this compound within the range of low concentrations is about three-fold higher than that of vinyl chloride. As there are no data with evidence that bromoethene is carcinogenic to humans, in Poland this compound is categorised into group 2, and according to the International Agency for Research on Cancer (IARC) into group 2A-probably carcinogenic to humans. A quantitative assessment of the carcinogenic effect of bromoethene, based on data on the incidence of hemangiosarcoma of the liver in rats exposed to this compound in concentrations of 44-1100 mg/m3, was adopted as the basis for calculating the MAC value. The concentration of bromoethene was calculated with the relationship between the concentration of bromoethene in the ambient air of the occupational environment and the probability of the development of hemangiosarcoma after 40-yr occupational exposure. A MAC value of 0.4 mg/m3 is suggested; it corresponds to the additional risk of hemangiosarcoma of 0.001. In population terms, this means that hemangiosarcoma of the liver may develop in one person per 1000 people exposed to bromoethene of 0.4 mg/m3 for 40 years. There are no grounds for setting the value of short-term maximum admissible concentration or the value of maximum concentration in the biological material for bromoethene.