Cancer Risk: Exposure to Nitrate and Pesticides

研究了周围环境中农业暴露导致癌症的危险因素，以估计这些环境暴露对农村人口癌症的贡献。农村人口接触到饮用水中的杀虫剂和硝酸盐，介于职业接触人群和一般人群之间。对非霍奇金淋巴瘤和脑癌、膀胱癌、结肠癌、直肠癌、胃癌、食道癌、胰腺癌和肾癌进行了病例对照研究。在这些病例对照研究中，为常规监测目的收集的水污染物数据库正被用来估计过去通过公共供水对个人的暴露。在内布拉斯加州，公共饮用水中硝酸盐水平的升高与非霍奇金淋巴瘤风险的增加有关。在暴露水平较低的明尼苏达州，一项对饮用水中硝酸盐的分析发现没有关联。这一假设在爱荷华州、西雅图和底特律地区正在进行的非霍奇金淋巴瘤病例对照研究中得到了进一步的研究。在一项涵盖美国12个州的生态研究中，以及在内布拉斯加州和科罗拉多州普拉特河谷的人口普查小组分析中，硝酸盐作为癌症风险因素的问题正在得到进一步探讨，那里的硝酸盐水平是全国最高的。我们还在开发新的方法，并改进现有的方法，在一般环境暴露研究中进行暴露评估，重点是杀虫剂和硝酸盐。这是为了更好地估计风险和发现此类研究中经常遇到的相对较小的风险增加所必需的。正在利用地理信息系统开发估计间接接触杀虫剂和估计私人水井接触硝酸盐和杀虫剂的新方法。遥感数据(卫星图像)和历史记录被用来估计内布拉斯加州和爱荷华州可能接触到农业杀虫剂的人口，因为他们的家园靠近经过杀虫剂处理的农田。这一方法也被用来改进加州的农药暴露评估，并与州农药使用报告数据库一起使用。爱荷华州和加利福尼亚州正在进行验证研究，以确定家庭中的杀虫剂水平与使用杀虫剂的农田附近之间的关系。正在使用土地覆盖、牲畜饲养场位置、土壤类型和其他信息的数据来估计私人水井中的硝酸盐水平。

Risk factors for cancer from agricultural exposures in the ambient environment are studied to estimate the contribution of these environmental exposures to cancer in the rural population. Rural populations have exposures to pesticides and nitrates in drinking water that are intermediate between occupationally-exposed groups and the general population. Case-control studies have been conducted on non-Hodgkin's lymphoma and cancers of the brain, bladder, colon, rectum, stomach, esophagus, pancreas, and kidney. Databases of water contaminants, gathered for routine monitoring purposes, are being used to estimate past exposures via public water supplies to individuals in these case-control studies. Elevated nitrate levels in public drinking water supplies were associated with an increased risk of non-Hodgkin's lymphoma in Nebraska. An analysis of nitrate in drinking water in Minnesota where exposure levels were lower found no association. This hypothesis is being investigated further in ongoing case-control investigations of non-Hodgkin's lymphoma in Iowa, Seattle, and the Detroit area. The issue of nitrate as a cancer risk factor is being pursued further in an ecologic study encompassing twelve states in the United States and in a census-block group analysis in the Platte River Valley of Nebraska and Colorado, where elevated nitrate levels are among the highest in the country. We are also developing new approaches, and improving existing methods, of exposure assessment in studies of general environmental exposures, with a focus on pesticides and nitrate. These are required to better estimate risk and to detect the relatively small increases in risk often encountered in such studies. Geographic information systems (GIS) are being utilized for developing new approaches to estimating indirect exposure to pesticides and for estimating exposure to nitrates and pesticides in private wells. Remote sensing data (satellite imagery) and historical records were used to estimate the population in Nebraska and Iowa potentially exposed to agricultural pesticides through the proximity of their homes to agricultural land treated with pesticides. This approach is also being used to improve pesticide exposure assessment in California in conjunction with the State pesticide use reporting database. Validation studies are underway in Iowa and California to determine the relationship between pesticide levels in the home and the proximity to agricultural land where pesticides have been applied. Nitrate levels in private wells are being estimated using data on land cover, livestock feedlot locations, soil type, and other information.