Estimations of risk from environmental asbestos in perspective.

Because very recent data on asbestos in the environment are available, some fairly firm conclusions can now be drawn regarding current exposure to asbestos fibres. If account is taken of occupational exposure data (where past exposure levels were very high indeed, leading to a very significant risk to workers at the time), it is possible to make some reasoned estimates of the risk from ambient air. In the past, there was considerable confusion regarding the degree of risk for both occupational and environmental conditions. In estimating the risk, account needs to be taken, in particular, of the fact that: (a) occupational exposures in the past were frequently higher than reported; (b) asbestosis (a disease only associated with very heavy occupational exposures) would seem to be mechanistically involved in the development of lung cancer associated with asbestos exposure; (c) chrysotile asbestos is now the commonest form of fibre used unlike in the past, when greater quantities of crocidolite and amosite were used, the latter types being much more closely associated with mesothelioma than chrysotile; (d) overall levels of asbestos in environmental ambient air are lower than they used to be; (e) ingested asbestos seems to be associated with a negligible degree of risk as indicated by animal and human studies. The estimated values of risk provided here are smaller than those published some years ago but are similar to those given in very recent key publications. The level of environmental lifetime risk from exposure to airborne asbestos would appear to be about 1 in 100,000 or even lower. Such a level of risk is exceedingly low, and bearing in mind the criteria of both WHO and the Royal Society of London, it would appear to represent an acceptable 'rare-event' extremely low-level risk, like the cancer risk from the cosmic radiation adsorbed when flying across the Atlantic or from eating charcoal broiled meat, or the risk of being killed by lightning.