Cancer Risk: Exposure to Nitrate and Pesticides

研究了周围环境中农业暴露的癌症风险因素，以估计这些环境暴露对农村人口癌症的影响。农村人口接触农药和饮用水中的硝酸盐，介于职业接触群体和一般人口之间。已经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，为例行监测目的收集的水污染物数据库被用来估计个人过去通过公共供水的暴露情况。内布拉斯加州公共饮用水供应中硝酸盐水平升高与非霍奇金淋巴瘤风险增加有关。明尼苏达州饮用水中的硝酸盐暴露水平较低，分析发现没有关联。在爱荷华州、西雅图和底特律地区进行的非霍奇金淋巴瘤病例对照研究中，正在进一步研究这一假设。硝酸盐作为癌症风险因素的问题正在一项包括美国12个州的生态研究中进一步探讨，并在内布拉斯加州和科罗拉多州的普拉特河谷进行了人口普查区组分析，那里的硝酸盐水平是全国最高的。我们还在一般环境暴露研究中开发新的暴露评估方法，并改进现有方法，重点是农药和硝酸盐。这些都需要更好地估计风险，并检测出相对较小的风险增加往往遇到这样的研究。目前正在利用地理信息系统开发新的方法，以估计间接接触农药的情况，并估计私人威尔斯井中接触硝酸盐和农药的情况。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的人口可能暴露于农业农药，因为他们的家园接近农药处理过的农田。这种方法也被用于改进加州的农药暴露评估，并与州农药使用报告数据库相结合。验证研究正在爱荷华州和加州进行，以确定家中农药水平与施用农药的农田附近之间的关系。私人威尔斯水井中的硝酸盐含量正在利用土地覆盖、牲畜饲养场位置、土壤类型和其他信息的数据进行估计。

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.