Authors
Shields T, Gridley G, Moradi T, Adami J, Plato N, Dosemeci M.

Title:
Occupational exposures and the risk of ovarian cancer in Sweden.

Journal:
American Journal Indian Medicine; 2002; 42(3):200-13

Summary:
Ovarian cancer is the sixth most common cancer in women. There have been many studies examining occupational and environmental exposure and the risk of ovarian cancer, but the results have been inconsistent, inconclusive or the studies poorly designed. This paper presents the results of a large study of ovarian cancer and occupation in a Swedish population. The authors of this study used the nationwide, population-based Swedish Cancer Environment Register (CER III) to investigate a possible association between ovarian cancer risk and all occupations and industries in Sweden. The data was collected from Swedish women employed during 1960-1970 and followed from 1971-1989. The occupations were classified using three-digit standard occupational codes. In this study only those industries and occupations with at least 20 ovarian cancer cases were used. Poisson regression was used to approximate the relative risk of ovarian cancer for particular occupation exposure. Analyses of occupational and industrial groups were adjusted only for attained age. This study also performed an occupational exposure assessment to classify each occupation and industry exposure to solvents, asbestos, diesel, ionizing, electromagnetic, and pesticides.

A total of 9,591 ovarian cancer cases were reported among 1,670,517 women. Long term exposure in some occupations showed an increased risk of ovarian cancer. Statistically significant, 50% or greater increases in the risk of ovarian cancer were noted for engineers and technicians in mechanical, chemical and other technical fields, religious workers, shoe workers, chocolate and candy workers, paper and packaging workers, wrapping, warehouse and supply room workers, psychologists, social workers, and clothes pressers relative to other women that reported employment in the same time period. The results also indicated that women who worked in specific occupations during both 1960s and 1970s were more likely at elevated risk of ovarian cancer than women who were reported that just worked during only one census. Consequently, long-term occupational exposures confer greater risk than short-term exposures.

In addition, the risk of ovarian cancer among dry cleaners has been studied broadly, but the accumulated evidence for an association was weak (Shen et al., 1998). In this study, laundry workers in 1960 and clothes pressers who worked in 1970 were associated with a significantly increased risk of ovarian cancer. The authors also found that women working in healthcare were commonly at a decreased risk of ovarian cancer. According to the results of this study, long-term work in the gardening industry presents an increased risk of ovarian cancer. Moreover, it has been suggested that increased incidence of ovarian cancer among teachers is often attributed to delayed onset or decreased incidence of childbearing. The relationship between occupational physical activities on ovarian cancer remains undefined and may serve as a better measure of overall physical activity and further study is required.

The extensive and detailed follow-up of ovarian cancer incidence, the size of the cohort, and the exposure assessment completed on two separate occasions, 10 years apart, are unique characteristics of this study. The use of job titles to suggest potential causative agents is a limitation of this study, as random misclassification of the individuals in the study may occur. Furthermore, the authors have not considered confounding factors such as lifestyle or oral contraceptive use and their relative effects on risk of ovarian cancer.