Cold, wet weather may mean more pollution, more prostate cancer
MedWire News: US researchers report evidence suggesting that the higher prevalence of prostate cancer in northern territories of the USA is linked with meteorological factors.
The team observed the strongest correlation between weather conditions and the disease in counties where climate affects the deposition, absorption, and degradation of persistent organic pollutants including pesticides.
“Some of these pollutants are known endocrine disruptors and have been associated with prostate cancer,” say Sophie St-Hilaire from Idaho State University, Pocatello, and colleagues in the International Journal of Health Geographics.
Previous research has linked prostate cancer incidence to a lower exposure to ultraviolet radiation in northern areas, leading to the hypothesis that lower vitamin D synthesis may increase the risk for prostate cancer.
To investigate further, St-Hilaire and team analyzed average shortwave radiation data for individual US counties, as well as other environmental factors such as average temperature, mean heating degree days, and average monthly snowfall.
The researchers observed a difference in prostate cancer incidence between counties in the upper and lower quartiles for each meteorological parameter. For instance, there were 163.7 cases per 100,000 in the third (top) quartile of snowfall versus 135.0 in the first (bottom).
The number of heating degree days (the annual sum of degrees Celsius required to attain an average temperature of 18.3℃) was positively correlated with prostate cancer, reflecting a negative correlation between temperature and the disease, notes the team.
Furthermore, in counties with large amounts of snowfall, pesticide use was positively associated with prostate cancer incidence, with an estimated 153 cases per 100,000 men when the average snowfall was 150 cm, in areas using 200,000 acres of land to grow crops (a proxy for pesticide use), compared with approximately 138 cases per 100,000 men in counties using the same area of land to grow crops, but which receive no snowfall.
“Snow trapping of atmospheric pollutants may compound the effect of pesticides by increasing the deposition of persistent organic pollutants,” explain the researchers.
Finally, controlling for all meteorological parameters, confounders (including premature mortality from heart disease and unemployment), and pesticide use explained 43% of the variation in incidence rates at county-level, compared with just 31% when controlling for shortwave radiation (vitamin D exposure) only.
“The trends detected in this study are consistent with the literature on environmental chemistry, which suggests meteorological parameters predispose northern climates to higher levels of pollutants,” conclude St-Hillaire et al.
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By Sarah Guy