Occupational and Environmental Factors

Cadmium and prostate cancer: a critical epidemiologic analysis

Cancer Investigation 23(3): 256-63, 2005
A E Sahmoun, L D Case, S A Jackson and G G Schwartz

Study purpose: Cadmium is a soft bluish metal related to zinc that has many industrial applications. Research from scientific laboratories suggests that cadmium is a carcinogen and a cause of prostate cancer. However, epidemiological studies looking at prostate cancer in large populations of men have been unable to find firm links between cadmium and prostate cancer. This epidemiologic analysis collects and studies the published medical literature on cadmium and prostate cancer in order to see if a link exists. It also focuses on industrial workers who have had potentially high levels of exposure to cadmium on the job.

Study description: Internet medical databases were searched from 1966 to 2002 for relevant studies. The researchers reviewed studies of factory workers with intensive exposure to cadmium in nickel-cadmium battery plants.

Findings: Five of ten case-control studies (50%) looked at found a link between prostate cancer and cadmium. Case-control studies compare a group with a disease against a similar but healthy group, and analyze their medical records and lifestyles to learn what factors may be linked with the disease. Three of 11 cohort studies examined (33%) also found a link (cohort studies compare a specific outcome in groups of individuals who are alike in many ways, but differ by a certain characteristic). Finally, another four cohort studies on workers exposed to nickel-cadmium batteries on the job were analyzed. No overall evidence was found showing a link.

Conclusions: The authors conclude that unlike studies done in scientific laboratories population studies of men do not show that cadmium is a cause of prostate cancer. No link was found between the two in studies of male workers in potentially high risk factory jobs.

Occupation-Related Pesticide Exposure and Cancer of the Prostate: a Meta-Analysis

Occupational and Environmental Medicine 60(9): 634-642, September 2003
G. Van Maele-Fabry and J. L. Willems

Study purpose: This Belgian meta-analysis estimates the risk of prostate cancer for workers who regularly use pesticides in their jobs or are habitually exposed to their use. A meta-analysis is a statistical method combining results from published studies in order to re-interpret overall evidence.

Study description: The meta-analysis surveyed 22 studies from 1995 to 2001 that looked at the risk of prostate cancer in pesticide-related occupations. The authors then calculated an overall estimate of the ratio of prostate cancer related risk called the “meta-rate ratio estimate.” This was compared to data from three previously published meta-analyses looking at prostate cancer risk for farmers.

Findings: Results showed that the meta-rate ratio estimate, based on 25 estimators or gauges of relative risk from 22 studies, showed an overall increase in relative prostate cancer risk of 1.13. Large differences in rate ratios existed among the different studies. Further analysis identified these as being largely due to geographic location and study methods. Overall, pooled risk estimates for studies from Europe were lower than those from Canada and the USA. A significant increase in risk was observed for men employed as pesticide applicators, whereas no increase was seen for farmers.

Conclusions: The increased meta-rate ratio for prostate cancer in occupations with regular exposure to pesticides is very similar to meta-rate ratios for prostate cancer risk in farmers calculated by three different meta-analyses from studies published before 1995. Although results do not identify pesticide exposure as a cause of prostate cancer, the fact that an increased meta-rate ratio was seen points to on-the-job exposure to pesticides as a possible factor. Future studies should focus on reliable methods to estimate exposure to pesticides.