Is there a safe level of exposure below which there is no risk?

Mesothelioma

There is a lack of scientific consensus as to whether there exists a threshold of exposure to asbestos below which a person is at zero risk of developing mesothelioma. However, there is evidence from epidemiological studies of asbestos exposed groups that any threshold for mesothelioma must be at a very low level – and it is fairly widely agreed that if a threshold does exists then it cannot currently be quantified. For practical purposes HSE does not assume that such a threshold exists.

Asbestosis and lung cancer

The situation for lung cancer and asbestosis is uncertain. Arguments for a threshold for lung cancer are based on the notion of the carcinogenic process being an extension of the chronic inflammatory processes producing fibrosis. It is generally recognised that heavy doses of white asbestos are required to produce clinically significant lung fibrosis. However, the situation for blue and brown asbestos is more uncertain and fibrosis has been observed at much lower exposures. This also suggests that if a threshold for lung cancer does exist for blue and brown asbestos it must be at a very low level indeed.