Cancer Risk and Environmental Exposures

研究环境中癌症的危险因素，以确定特定的化学物质和污染物类别，调查其作用机制，并估计环境因素对普通人群癌症的贡献。暴露包括饮用水污染物，特别是消毒副产物、硝酸盐和砷；家中空气中的氡；氯代烃的居住水平和人体负荷；环境和室内空气污染物，以及工业排放物。爱荷华州的病例对照研究表明，长期饮用饮用水中的消毒副产物后，男女患直肠癌和膀胱癌和脑癌的风险都很高。正在对这些数据进行分析，并改进和更新对消毒副产物暴露的评估。在西班牙，长期暴露于消毒副产物后膀胱癌发病率升高，基因型为GSTT1（+）或GSTZ1 （SNP rs1046428）的人群风险增加。还观察到膀胱癌的风险与通过非摄入途径（例如吸入或皮肤吸收）暴露于dbp有关。我们目前正在新英格兰的一项病例对照研究中评估这一假设。爱荷华州公共供水中的硝酸盐水平与膀胱癌和胰腺癌的风险无关。我们观察到，在亚硝化能力增强的亚组中，结肠癌和肾癌的风险增加，这分别是由于他们摄入了更多的饮用水硝酸盐，摄入了更少和更多的维生素C和红肉。爱荷华州妇女健康研究（一项针对爱荷华州老年妇女的队列研究）发现，在公共供水中摄入较高浓度的硝酸盐以及较高的饮食摄入量与患甲状腺癌、卵巢癌和膀胱癌的风险增加有关。饮食中硝酸盐的摄入与甲状腺功能减退有关。私人井中硝酸盐含量的升高与亚cli患病率的增加有关

Risk factors for cancer from the ambient environment are studied to identify specific chemicals and classes of contaminants, to investigate mechanisms of action, and to estimate the contribution of environmental factors to cancer in the general population. Exposures include drinking water contaminants, especially disinfection byproducts, nitrate, and arsenic; airborne radon in homes; residential levels and body burdens of chlorinated hydrocarbons; ambient and indoor air pollutants, and emissions from industrial sources. Case-control studies in Iowa showed excess risks for rectal cancer in both sexes and bladder and brain cancers among men after long-term consumption of disinfection byproducts in drinking water. Analysis of these data with an improved and updated assessment of exposure to disinfection byproducts is ongoing. Bladder cancer in Spain was elevated after long-term exposure to disinfection byproducts, with enhanced risk among persons with genotypes GSTT1 (+) or GSTZ1 (with SNP rs1046428). It was also observed that risk of bladder cancer was associated with exposure to DBPs through routes other than ingestion (e.g., inhalation or dermal absorption). We are currently evaluating this hypothesis in a case-control study in New England. Nitrate levels in public water supplies in Iowa were not associated with risk of bladder and pancreas cancer. We observed increased risks of colon and kidney cancer among subgroups with increased nitrosation ability due to their higher intake of drinking water nitrate and lower and higher intakes of vitamin C and red meat, respectively. Ingestion of higher nitrate concentrations in public water supplies as well as higher dietary intake was associated with increased risk of thyroid, ovarian, and bladder cancers in the Iowa Womens Health study, a cohort study of older women in Iowa. Dietary nitrate intake was associated with hypothyroidism. Higher nitrate levels in private wells were associated with increased prevalence of subcli