北京城市道路灰尘重金属污染的健康风险评价

道路灰尘是城市中一类重要的环境介质,人群可通过吸入、摄食及皮肤接触3种途径摄入灰尘中的污染物,长期暴露在灰尘环境中会对人体造成慢性伤害.为探索北京城市道路灰尘中重金属污染的潜在健康风险,本研究于2009年对北京城市道路网络地表灰尘进行调查并获得有效样品225个.研究测定了样品中常见重金属Cd、Cr、Cu、Mn、Ni和Pb的总含量,并应用美国环保署(U.S.EPA)人体暴露风险评价方法进行评价.结果表明,研究区域道路地表灰尘中重金属Mn、Ni的平均含量略低于北京市的土壤背景值,Cr含量略高于土壤背景值,Cu、Pb均值为背景值的2～3倍,Cd含量几乎超出背景值的5倍.不同途径重金属慢性每日平均暴露量排序为:手-口摄食途径>皮肤接触途径>吸入途径.重金属成人非致癌风险排序为Cr>Mn>Pb>Cu>Ni>Cd,儿童非致癌风险排序为Cr>Pb>Mn>Cu>Ni>Cd,均小于非致癌风险阈值;重金属致癌风险排序为Cr>Ni>Cd,均低于致癌风险阈值,其中以Cr和Pb的潜在健康风险最高.对比采样涉及的各行政区内儿童非致癌风险均值发现,风险值随城市功能区定位呈现梯度变化,即首都功能核心区>城市功能拓展区>城市发展新区.Cu、Ni和Pb的健康风险与人口密度、建筑用地等因子显著相关,其含量受人为活动的影响较大,应加强管理控制其风险.

Health risk assessment of heavy metals of street dust in Beijing

Street dust is an important environmental pollutant in urban area. Long-term exposure to the dust environment would cause chronic damage through ways of inhalation, ingestion, and dermal taken. In order to evaluate the potential health risk of street dust in Beijing, an extensive survey was conducted in the urban areas within the Sixth-Ring Road. Totally 225 dust samples were collected from the street surfaces in September 2009 and their concentrations of Cd, Cr, Cu, Mn, Ni, and Pb were determined. Human health risk assessment method established by U.S. EPA was used to evaluate the potential health risk of those heavy metals in the street dust. Except for Mn and Ni, the average heavy metal concentrations in the street dust were all higher than the background values of Beijing, where Cr was slightly higher, Cu and Pb were 2~3 times higher, and Cd was 5 times higher than the background values. The way of chronic daily average exposure was ingestion > dermal taken > inhalation. The non-cancer risk of exposure was Cr>Mn>Pb>Cu>Ni>Cd for adult and Cr >Pb>Mn >Cu>Ni>Cd for children, while the cancer risk of exposure was Cr>Ni>Cd. All the risks were lower than the average risk thresholds of the heavy metals, and would therefore not cause carcinogenic health hazard to human body. Generally, the most potentially harmful heavy metals in Beijing urban area were Cr and Pb. Moreover, a comparison among the 14 districts of Beijing with the non-cancer risk for children showed that downtown > expanding urban area > developing urban area, indicating significant relationship with district function. The health risks of Cu, Ni, and Pb were correlated with population density and the proportion of built-up area. Therefore, proper measures should be taken for the dust risk management in terms of human activities.