Pellizzari E, Lioy P, Quackenboss J, Whitmore R, Clayton A, Freeman N, Waldman J, Thomas K, Rodes C, Wilcosky T
Research Triangle Institute, Research Triangle Park, North Carolina 27709, USA.
J Expo Anal Environ Epidemiol. 1995 Jul-Sep;5(3):327-58.
The National Human Exposure Assessment Survey (NHEXAS) Phase I study is designed to be part of the total NHEXAS framework developed from a series of scientific discussions and workshops conducted by the U.S. Environmental Protection Agency (EPA) during 1992 and 1993. NHEXAS examines total human exposure and is structured to include: Phase I, scoping studies; Phase II, a full national exposure survey; and Phase III, a series of highly focused characterization modules. Our research program examines the scientific issues important to Phase II, including statistical sampling, methods evaluation, media concentration measurements, formulating quality assurance goals, and identification of important pathways leading to exposure. To determine the feasibility of NHEXAS in characterizing human exposure for a representative population, a hypothesis-driven design is used to answer important questions about human exposure to specific environmental contaminants. This paper describes: (1) hypotheses to be tested; (2) contaminants selected for study; (3) strategies for measuring exposure; (4) study area and population; (5) population sampling design; (6) media sampling and analysis procedures; and (7) data analysis. The contaminants of concern in this Phase I study include selected metals and volatile organic compounds. From these classes the first-tier contaminants to be measured are lead, arsenic, benzene, chloroform, perchloroethylene, and trichloroethylene. Contaminants selected for examination may potentially be found in many media (personal-nonoccupational, personal-occupational, indoor, and outdoor residential air; dust; potable water; food/beverages; soil; blood; hair; and urine) and exposures may occur by multiple routes (inhalation, ingestion, dermal). The central hypothesis of our field study is to discover whether individual and population exposures determined by modeled or extant data are/are not significantly different from those determined directly from multipathway and multimedia measurements. In addition, there are a series of subhypotheses ranging from pollutant-specific exposure measurement and body burden hypotheses to the optimization of exposure models. In keeping with the NHEXAS framework, a probability-based population sample for total exposure and the field study will be conducted in counties located throughout EPA Region 5 (Minnesota, Wisconsin, Illinois, Indiana, Ohio, and Michigan). Sampling units will be households and an individual residing within each household. Environmental, exposure, and biological media sample collection will be performed by this consortium. Analyses of the external media and biological media samples will be completed by this consortium or Federal laboratories of the Centers for Disease Control and Prevention (CDC), Food and Drug Administration (FDA), or EPA. The protocols and analytical techniques selected for use represent the best available for total exposure assessment at this time.
国家人类暴露评估调查（NHEXAS）第一阶段研究旨在成为美国环境保护局（EPA）在1992年和1993年通过一系列科学讨论和研讨会制定的整个NHEXAS框架的一部分。NHEXAS研究人类的总体暴露情况，其结构包括：第一阶段，范围界定研究；第二阶段，全国性全面暴露调查；第三阶段，一系列高度聚焦的特征描述模块。我们的研究项目探讨了对第二阶段很重要的科学问题，包括统计抽样、方法评估、介质浓度测量、制定质量保证目标以及确定导致暴露的重要途径。为了确定NHEXAS在描述代表性人群的人类暴露情况方面的可行性，采用了一种假设驱动的设计来回答有关人类接触特定环境污染物的重要问题。本文描述了：（1）待检验的假设；（2）选定用于研究的污染物；（3）测量暴露的策略；（4）研究区域和人群；（5）人群抽样设计；（6）介质抽样和分析程序；以及（7）数据分析。本第一阶段研究中关注的污染物包括选定的金属和挥发性有机化合物。从这些类别中，首批要测量的污染物是铅、砷、苯、氯仿、全氯乙烯和三氯乙烯。选定用于检测的污染物可能在多种介质中被发现（个人非职业、个人职业、室内和室外住宅空气；灰尘；饮用水；食品/饮料；土壤；血液；头发；以及尿液），并且暴露可能通过多种途径发生（吸入、摄入、皮肤接触）。我们实地研究的核心假设是，确定由模型或现有数据得出的个体和人群暴露与直接通过多途径和多媒体测量得出的暴露是否存在显著差异。此外，还有一系列子假设，从特定污染物的暴露测量和体内负荷假设到暴露模型的优化。按照NHEXAS框架，将在EPA第5区域（明尼苏达州、威斯康星州、伊利诺伊州、印第安纳州、俄亥俄州和密歇根州）的各县进行基于概率的总体暴露人群样本和实地研究。抽样单位将是家庭以及每个家庭中的一名居民。该联盟将进行环境、暴露和生物介质样本的采集。外部介质和生物介质样本的分析将由该联盟或疾病控制与预防中心（CDC）、食品药品监督管理局（FDA）或EPA的联邦实验室完成。所选用的方案和分析技术代表了目前可用于总体暴露评估的最佳方法。
