Health Stream Literature Summary - Issue 56 - December 2009

Bladder cancer incidence and mortality rates compared to ecologic factors among states in America.
Colli, J.L. and Kolettis, P.N. (2009) International Urology and Nephrology. doi: 10.1007/s11255-009-9655-5

Smoking is believed to be the main cause of bladder cancer (BCa) and may account for about 50% of cases in developed countries. There is some evidence to suggest that vitamin D is protective against a variety of cancer types. Inadequate exposure to sunlight or solar ultraviolet radiation, which stimulates Vitamin D production in the body, has been implicated as a cause of premature mortality from several cancers in America including BCa. Exposure to pesticides has also been associated with increased BCa risks in some studies. The American population is exposed to very low levels of pesticides in drinking water and the levels vary depending on the source of the water. Pesticides and degradates are generally present in surface water and less common in groundwater. In addition to pesticides, arsenic and chlorination by-products have been linked to bladder cancer in some studies. Arsenic naturally occurs more often in groundwater than surface water. In this study the BCa incidence and mortality rates were compared to cigarette smoking, solar UV radiation levels and the percentage of the population drinking water from a surface water supply on a state-by-state basis. Family income, lack of health insurance and urbanisation were included to adjust for access to health care and socioeconomic status. Data were obtained from a range of sources and bladder cancer incidence and mortality rates for males and females were compared to the variables studied on a state-by-state basis.

Incidence rates of bladder cancer for both genders correlated inversely with levels of solar UV radiation and directly with cigarette smoking. Also incidence rates correlated inversely with lack of health insurance for females and were suggestive but not statistically significant for males. Mortality rates for both genders correlated inversely with levels of solar UV radiation and directly with cigarette smoking and drinking from a surface water supply. Stepwise multiple regression analysis of the independent variables with bladder cancer rates was used to identify the best fit variables for predicting incidence and mortality rates in males and females. Solar UV radiation was the best predictor of BCa incidence in males and solar UV radiation and smoking in females. Solar UV radiation, smoking and drinking surface water were the best predictors of BCa mortality in males, while smoking and drinking surface water were the best predictors of mortality in females.

The authors suggest correlations found in this study between BCa mortality risks and drinking surface water may be a result of residual pesticide contamination that is found in surface at much higher levels than in groundwater. However the results of previous studies examining the association between pesticides and BCa risks have been inconsistent. Genotoxic by-products of chlorine disinfection of drinking water may also play a role.

Comment This ecological study used state-level statistics and thus did not examine individual exposures or risk factors. The assumption that drinking water from surface sources contains pesticides appears to come from UGS surveys on source waters rather than measurements of treated drinking water.

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