Non-Hodgkin's lymphomas and occupation in Sweden

Objectives: To investigate whether there is a risk excess of non-Hodgkin's lymphoma among Swedish workers associated with particular occupations. Methods: The base population was made up of Swedish men (1,779,646) and women (1,101,669) who were gainfully employed at the time of the 1970 census, had also been present in the 1960 census and were still alive and older than 24 years as of 1 January, 1971. They were followed up for 19 years until the end of 1989. Age- period standardised incidence ratios were computed in a dataset linking cancer diagnoses from the Swedish national cancer register to occupational and demographic data obtained in the census of 1970. Log-linear Poisson models were fitted, allowing for geographical area. Risk estimators per occupation were also computed for workers reporting the same occupation in 1960 and 1970, a more specifically exposed group. Results: There were 7,610 non-Hodgkin's lymphomas reported in the study cohort, 5,391 cases in men and 2,219 in women. A relative risk of over 1.20 and statistically significant was observed in men among accountants and auditors, secretaries and typists, auctionists, non-specified rail and road transport workers, telecommunications traffic officers, telegraph and radio operators, photographic-laboratory workers and other production and related work. The risk excess was confirmed in men with the same occupation in both censuses. In women, only three occupations achieved statistical significance: metal platers and coaters, truck and conveyor operators and store and warehouse workers. Conclusions: The risk excess observed in telecommunication and transport workers could be explained by electromagnetic radiation exposure. We did not find a risk excess in agricultural occupations, that has been largely documented by other study groups.