Investigating cancer risks related to asbestos and other occupational carcinogens

It has been half a century since asbestos was recognised as a lung carcinogen.1 Asbestos may well be the most studied occupational carcinogen and it is indeed virtually an icon for industrial carcinogenesis. National bodies have taken action to restrict or ban asbestos use and analogous international initiatives have been undertaken as well.2 Asbestos use has been sharply curtailed in developed countries, though the same is not true in developing countries.3,4 Even if it were eliminated in all new uses, asbestos would still remain in the occupational environment, especially in construction trades,5,6 and it would remain in the general environment, both from past industrial/consumer products and from erosion of natural outcroppings of asbestos-containing rock.7 Despite the large number of studies that have examined asbestos, there are important questions which are still controversial, such as differences in risk by fibre type, by industry and by level of exposure.8,9

Whereas most of the studies that have identified high risks of lung cancer were cohort studies among workers whose exposure was mainly in the period 1940–70, studies conducted on more recently exposed workers, and studies using case-control methods, have generally not found clear evidence of excess risks of lung cancer. This may well be due to lower exposure levels, shifts …