Asbestos Exposure

Asbestos is a mineral compound widely used as insulating material and inhalation of fine asbestos particles can, after 20 or more years, result in lung disease including lung cancer. The British Lung Foundation calculates that the peak incidence of asbestos-induced lung disease, which kills 30 people per week, will occur in the UK between 2011 and 2015.
Attempts to lower the risk of cancer developing in those exposed to asbestos by use of high dose supplements have been unsuccessful and in some instances have resulted in an increase in the risk of developing cancer.  Asbestos is classified by the World Health Organisation as a class A carcinogen. 
The impact of asbestos on insurance and prevalence of the problem in the UK is contained in a detailed report prepared by a committee form the Institute of Actuaries under the chairmanship of Julian Lowe.  They estimated in 2004 that the number of asbestos-related claims (for pleural plaques/thickening, asbestosis, lung cancer and mesothelioma) could be as high as 198,000 in the UK.
www.actuaries.org.uk/__data/assets/pdf_file/0004/34969/Lowe.pdf
For a world view, courtesy of Mohammad Khan of Price Waterhouse Coopers, see www.actuaries.org.uk/__data/assets/pdf_file/0018/30672/Khan.pdf (2006)

Beta-carotene
Large trials using very high doses, 20 to 30 mg per day, of beta-carotene in those exposed to asbestos showed either no reduction or an increase in the risk of cancer developing.  As a result of these trials in May 2003 “the Expert Committee on Vitamins and Minerals advises that, as a matter of prudence, smokers or those exposed to asbestos should not take beta-carotene supplements.” www.food.gov.uk/multimedia/pdfs/vitmin2003.pdf
The US expert position is that beta-carotene should only be used for the correction of vitamin A deficiency, which, in adults, is very rare. 

Vitamin A
Supplements of retinol were not associated with an increased risk of cancer in the trials involving those exposed to asbestos but in other trials there does appear to have been an increase in cancer rate overall and thus it would be prudent not to exceed the Safe Upper Level of 1500 ug per total intake, which typically means not exceeding 800 ug per day from supplements.

The British Lung Foundation is a UK charity established in 1985 which provides information and support for those affected by lung disease.  It provides information on asbestosis.