Research shows possible connection between pesticide use and skin cancer

Health researchers have been unable to explain why several studies have found an excess risk of melanoma and other skin cancer for farmers. Farmers spend time in the sun — which is a major risk factor — but could it be something else? New research suggests that exposure to certain pesticides could be one of the causes. Epidemiologists from the University of Iowa, NIH and the National Cancer Institute used data collected from a group of licensed pesticide applicators in Iowa and North Carolina to determine if melanoma incidence was correlated with the use of any of 50 pesticides. After correcting for typical melanoma health risks and other factors (following standard epidemiological protocol), they found increased risks for those exposed to maneb/mancozeb, parathion and carbaryl (see note below for risk details). (Environmental Health Perspectives)

The study’s results are another reminder that although lists of pesticide residues like EWG’s Dirty Dozen/Clean Fifteen can help consumers avoid pesticides, the effects of pesticides are felt far and wide. A newsletter from San Francisco-based CUESA eloquently examined this issue.

Note: for maneb/mancozeb, the odds ratio was 2.4 (i.e., the rate of melanoma for the study group was 2.4 times higher than the general population), with a 95% confidence interval of 1.2-4.9 for 63+ exposure days. For parathion, the odds ratio was 2.4, 95% confidence interval of 1.3-4.4 for 56+ exposure days. For carbaryl, the odds ratio was 1.7, 95% confidence interval of 1.1-2.5 for 56+ exposure days.

3 Responsesto “Research shows possible connection between pesticide use and skin cancer”

  1. I’m shocked, just shocked! Chemicals we trust causing cancer!?!

    Well, there is a great control group for this study – organic farmers. We, like most organic farmers, have never used herbicides, pesticides and other -cides. I and the land owner before us banned the power companies from using their -cides on our land so our land has been clean for 50(?) years or so. Since it was sheep land before that it may never have seen -cides. Places like ours with their populations of unexposed or minimally exposed farmers would be excellent comparisons for this research.

  2. Although I haven’t read the paper, I wanted to point out that when you look at large numbers of measurements, some come up positive due to chance alone. If you made 100 observations, and restricted ‘hits’ by a 95% confidence interval, you would on average have 5 of them come up as positive hits. So if you look at 50 different pesticides, you will have 2.5 of them come up as positive hits at the 95% confidence level – they had 3. Certainly, this means they should follow up by taking a closer look at these pesticides, but it is also possible that some of these are false positives.

  3. That there were 50 pesticides examined seems the most chancy part of this, as the Agricultural Heath Study database would have allowed the researchers to just as easily present results for only the 6 fungicides (1 of the 6 was associated with significantly higher risk), or only those that had significant associations, or only the take-home questionnaire respondents, etc.  The database also allowed the epidemiologists to examine risks from each pesticide independently, since not all subjects were exposed to each pesticide or to the same amount of each one.   Of course, there is always the possibility that confounding, uncertainty of actual exposure to the chemicals (e.g., variations in effectiveness of protective equipment), genetic factors and so on could affect the results, and the authors conclude that “our study suggests more research is needed on chemicals and other environmental factors that may increase the risk of cutaneous melanoma.”