Numerous epidemiological studies have investigated the role of occupational exposures in causing lung cancer (other than mesothelioma) and, despite the many difficulties of such studies, several occupational agents and jobs have been identified as definite or probable causes. A large number of potential occupational agents are known to be human lung carcinogens (see chapter 7 , table 7). Depending on the agent, as well as on methodological aspects, additive or multiplicative modes of interaction have been shown to operate with cigarette smoking. Established carcinogenic processes relevant to the lung include coke production and coal gasification (possibly related to polycyclic aromatic hydrocarbons), iron and steel founding, paint manufacture and painting. Occupational exposure to diesel exhaust and environmental tobacco smoke are also causes of lung cancer, although the magnitude of risk is smaller than that found for the established carcinogenic agents. However, to take diesel exposure as an example, the population at risk of exposure within the workforce is large, leading to a potentially high burden of disease.
The contribution of occupation to the causation of lung cancer has been shown to be considerably larger than for most other common cancers. The most frequently quoted estimate is 15% in men and 5% in women, although higher population-attributable risks have been reported (24% overall, 29% in men and 5% in women) for the contribution of occupational exposure. In all studies, occupational asbestos exposure is considered the most influential factor. A prospective cohort study in the Netherlands estimated that 12% of cases of lung cancer in men were attributable to lifetime occupational asbestos exposure, after adjustment for smoking and diet. The total burden of lung cancer cases attributable to work-related exposure to respiratory carcinogens in Europe has been estimated to be 32 400 cases per year.
In spite of such high estimates of the quantitative contribution of occupational factors in the aetiology of lung cancer, it is a common feature of all compensation agencies or notification systems that very few lung cancers of occupational origin are reported. There are several reasons for such under-reporting: occupational lung cancer almost always occurs among (former) smokers; the clinical presentation of occupational lung cancer is generally similar to that of non-occupational lung cancer; therapeutic options do not differ between occupational and non-occupational lung cancer; causal inferences have to be based on estimated probabilities that the disease is work related in an individual patient. However, the notion of occupationally induced lung cancer is important in terms of prevention, and European efforts to detect and reduce occupational carcinogenic exposures must continue.
Further information on lung cancer can be found in chapter 19.