Ambient exposures to selected volatile organic compounds and the risk of prostate cancer in Montreal

Abstract

Little is known about environmental factors that may increase the risk of prostate cancer. We estimated associations between incident prostate cancer and environmental concentrations of five ambient volatile organic compounds (VOCs): benzene; n-decane; ethylbenzene; hexane; and 1,2,4-trimethylbenzene.

Methods: This study is based on a population-based case-control study of incident prostate cancer (PROtEuS) in men ≤ 75 years of age living in Montreal, Canada, in 2005 to 2012. We included 1172 cases and 1177 population controls. We had personal information, lifetime residential addresses, occupational exposures, and a variety of area-wide covariables. We inferred concentrations of the five VOCs using Bayesian geostatistical models using data from a dense environmental survey conducted in Montreal in 2005 to 2006. We used different sets of adjustments to estimate odds ratios (OR) and confidence intervals.

Results: We found nonlinear associations such that the ORs increased monotonically and then either flattened or fell off with increased exposures. The model that contained other environmental variables and contextual variables led to lower ORs and results were similar when we restricted analyses to controls recently screened or tested for prostate cancer or cases with low- or high-grade tumors. A change from the 5th to 25th percentile in mean environmental benzene levels led to an adjusted OR of 2.00 (95% confidence interval = 1.47, 2.71).

Conclusion: We found positive associations between prostate cancer and concentrations of benzene and ethylbenzene, independently of previous testing for prostate cancer or tumor grade, suggesting that exposure to certain ambient VOCs may increase incidence.

Keywords: 1,2,4-Trimethylbenzene; Benzene; Case-control study; Ethylbenzene; Hexane; Population-based; Prostate cancer; Volatile organic compounds; n-Decane.

Figure 1.

Marginal, age-adjusted response functions for the risk of prostate cancer for each of the five VOCs measured using mean values. The units for the exposures are in µg/m³. The solid line represents the maximum likelihood estimates using a natural cubic spline function on 3 degrees of freedom. The gray band shows the pointwise 95% confidence interval and the rug plot at the top refers to values for cases and the bottom refers to controls. A, Mean values of benzene. B, Mean values of n-decane. C, Mean values of ethylbenzene. D, Mean values of hexane. E, Mean values of 1,2,4-trimethylbenzene.