Cancer Risk and Environmental Exposures to Nitrate, Pest

研究了周围环境中的农业化学品导致癌症的风险因素，以估计这些环境暴露对农村人口癌症的影响。农业地区的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。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。然而，饮食中亚硝酸盐的摄入量增加与胰腺癌的风险增加有关。总体而言，饮用水硝酸盐水平与结肠癌、直肠癌和肾癌的风险无关;然而，亚硝化能力增加的特定亚组患结肠癌和肾癌的风险增加。在硝酸盐摄入量较高、红肉摄入量较高或维生素C摄入量较低的人群中，结肠癌和肾癌的OR值均升高约两倍。内布拉斯加州公共供水中硝酸盐含量升高与神经胶质瘤风险无关。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。在最近完成的一项非霍奇金淋巴瘤病例对照研究中，对这一假设进行了调查，该研究在四个中心进行：爱荷华州、西雅图、洛杉矶和底特律地区。从1960年起，公共供应的硝酸盐监测数据与水源历史有关。在访谈家庭的私人威尔斯井测量硝酸盐。我们将大多数分析限制在自1960年以来硝酸盐估计值>70%的人年（181例，142例对照）。我们发现，与平均饮用水硝酸盐的最高四分位数（>2.90 mg/L硝酸盐-N：OR=1.2，95% CI 0.6-2.2）或与> 5 mg/L的年份（10年以上：OR=1.4，95% CI 0.7-2.9）没有总体关联。我们没有发现饮用水硝酸盐暴露与维生素C摄入或红肉摄入（分别是体内NOC形成的抑制剂和前体）之间相互作用的证据。膳食硝酸盐与NHL风险呈负相关（最高四分位数OR=0.54，95%CI 0.34-0.86）。膳食亚硝酸盐摄入量与风险增加相关（最高四分位数OR=3.1，95%CI 1.7-5.5），主要是由于摄入面包和谷物来源的亚硝酸盐。在内布拉斯加州和科罗拉多州的普拉特河谷进行的一项生态学研究中，硝酸盐作为癌症风险因素的问题正在进一步探讨，那里的硝酸盐水平是全国最高的。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。我们还在一般环境暴露研究中开发暴露评估的新方法，并改进现有方法，主要侧重于农药和硝酸盐。需要这些更好的方法来更好地估计风险，并检测在此类研究中经常遇到的相对较小的风险增加。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和估计接触私人威尔斯的硝酸盐的情况。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。

Risk factors for cancer from agricultural chemicals in the ambient environment are studied to estimate the contribution of these environmental exposures to cancer in the rural population. Rural populations in agricultural areas 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. Nitrate levels in public water supplies in Iowa were not associated with risk of bladder and pancreas cancer. However, higher intakes of dietary nitrite were associated with an increased risk of pancreas cancer. Overall, drinking water nitrate levels were not associated with risk of colon, rectal, and kidney cancer; however, specific subgroups with increased nitrosation ability were at increased risk of colon and kidney cancer. Among those with higher water nitrate intake and higher red meat intake or lower vitamin C intake, ORs were elevated about two-fold for both colon and kidney cancers. Elevated nitrate in public water supplies in Nebraska was not associated with risk of glioma. Elevated nitrate levels in public drinking water supplies were associated with an increased risk of non-Hodgkin's lymphoma in Nebraska. This hypothesis was investigated in a recently completed case-control investigation of non-Hodgkin's lymphoma in four centers: Iowa, Seattle, Los Angeles and the Detroit area. Nitrate monitoring data for public supplies was linked to water source histories from 1960 onwards. Private wells at interview homes were measured for nitrate. We limited most analyses to those with nitrate estimates for >70% of their person-years since 1960 (181 cases, 142 controls). We found no overall association with the highest quartile of average drinking water nitrate (>2.90 mg/L nitrate-N: OR=1.2, 95% CI 0.6-2.2) or with years >5mg/L (10+ years: OR=1.4, 95% CI 0.7-2.9). We saw no evidence of an interaction between drinking water nitrate exposure and either vitamin C intake or red meat intake, an inhibitor and precursor, respectively, of in vivo NOC formation. Dietary nitrate was inversely associated with risk of NHL (highest quartile OR=0.54, 95% CI 0.34-0.86). Dietary nitrite intake was associated with increasing risk (highest quartile OR=3.1, 95% CI 1.7-5.5), largely due to intakes of bread and cereal sources of nitrite. The issue of nitrate as a cancer risk factor is being pursued further in an ecologic study of census-block groups in the Platte River Valley of Nebraska and Colorado, where elevated nitrate levels are among the highest in the country. Nitrate levels in private wells are being estimated using data on land cover, livestock feedlot locations, soil type, and other information. We are also developing new approaches, and improving existing methods, of exposure assessment in studies of general environmental exposures, with a primary focus on pesticides and nitrate. These better methods 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 nitrate 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.