Occupational risk factors of lung cancer in a French

A case-control study of 1625 histologically confirmed cases of lung cancer and 3091 controls matched for sex, age, hospital admission, and interviewer was conducted in France between 1976 and 1980. The results presented concern the effects of different occupations on the occurrence of lung cancer among 1334 male cases and 2409 matched controls. Occupations were coded blindly according to the International Standard Classification of Occupations. An excess risk of lung cancer was observed for the following occupations after adjustment for cigarette exposure: farmers (RR = 1 24, p < 0-06), miners and quarrymen (RR = 2-14, p < 0 02), plumbers and pipe fitters (RR = 180, p < 0-04), motor vehicle drivers (RR = 1-42, p < 0-01). With present knowledge, it is difficult to make any precise estimate of the proportion of cancers attributable to occupation. For lung cancer, smoking habits have to be taken into account since the prevalence of cigarette smoking varies with occupational status. This was seen illustrated in France' and in England.2 A close association between average smoking habits for each occupational order and lung cancer mortality has been described.2 Doll and Peto attributed 15% ofmale and 5% of female cases of lung cancer in the United States to occupational factors.3 At present several occupations are recognised by the International Agency for Research on Cancer (IARC) to have an increased risk of lung cancer causally related to the occupation,45 those affected include some subgroups of the following occupations: agriculture, forestry and fishing, asbestos production, metal industry, shipbuilding, chemical industry, pesticide and herbicide production, extractive occupations, gas industry, and construction industry. Moreover, an increased risk of lung cancer was reported for other subgroups among these occupations but for which the assessment of the causal relation with the occupation was not definitive. The results here concern occupations already known or suspected to be associated with lung cancer in France. They have been taken from an international case-control study performed to study smoking habits. Accepted 6 April 1987 Material and methods A complete description of the study may be found in previous reports.6" In France 1625 cases with histologically confirmed lung cancer and 3091 controls whose current diseases were not related to tobacco were included between 1976 and 1980. Each case was matched with one or two controls on sex, age at diagnosis (±5 years), hospital of admission, and interviewer. The questionnaire included questions about place of residence since birth, educational level, occupation, and smoking and drinking habits. A complete occupational history was recorded. Respondents were asked to give their occupations, from the most recent to the first, with the corresponding duration (at least one year). These data were previously coded according to chemical or physical exposures determined by a panel of experts, such as coal dust, gasoline, or asbestos. The data were recoded blindly using the International Standard Classification of Occupations.8 Since most women had no occupation, and since few men smoked cigars and pipes, these categories were excluded and the results limited to male non-smokers or exclusively cigarette smokers. All the analyses were performed with adjustment for cigarette status. The effect of each occupational exposure was estimated by a matched logistic regression9 taking into account cigarette exposure defined by age at the first cigarette (non-smokers, 20 years or more, less than 20 years), daily consumption of cigarettes (non-smokers, less than 20 cigarettes a day, and 20 cigarettes or more a 231 group.bmj.com on November 6, 2017 Published by http://oem.bmj.com/ Downloaded from