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A critical issue in epidemiological studies of ambient air pollution is the measurement of pollutant exposure in the study population. Accurate characterization of air quality is necessary in any study relating exposure to health effects, and is essential in attempting to quantify risk estimates for specific exposure concentrations. Despite the importance of accurate air quality data, most epidemiological investigations have used relatively crude estimates of pollutant exposure. Results from such investigations may be only qualitative at best., Early studies of air pollution health effects were limited by a lack of air pollution monitoring sites, and thus, exposures were often based on surrogate measures such as tons of coal consumed. With the introduction of reliable and reasonably accurate measurements of pollutant concentrations, several important constraints remained. These limitations include the relatively sparse siting of monitor sites and the variable relationship of monitor concentrations to the exposure experience of the study population. Other considerations in using monitor data include the selection of the pollutant specie(s), the duration of the sampling period, the use of short-term versus long-term averages, peak versus mean concentrations and the cyclical variation in pollutant levels., The Chestnut Ridge region of Pennsylvania is the site of an ongoing study of health effects from air pollution. This site was selected in part because of the extensive and well maintained air pollution monitoring network, and the previous studies of pollutant dispersion in the area. Several studies of respiratory symptoms and pulmonary function in women and school age children have been carried out in the area. The current study evaluated aspects of air pollution exposure estimates which are relevant to these epidemiologic studies. Subsequent papers will discuss findings of the various epidemiologic studies which employ these air pollution measures.

This study was undertaken to aid in the evaluation of Environmental Monitoring Plans (EMP) submitted to the U.S. Synfuel Corporation by prospective operators of large-scale synfuel plants who are applying for financial assistance. In accordance with the Energy Security Act of 1980, such applicants must provide an acceptable EMP in order to qualify for the assistance. The EMP is reviewed in consultation with the U.S. Environmental Protection Agency (EPA) and the Department of Energy. This study was sponsored by EPA to aid in their consultative role., The study is limited to evaluating the ambient monitoring plan of the EMP. Ambient monitoring we interpret as pertaining to the surveillance and measurement of pollutants that may emanate from the synfuel complex but are found outside the perimeter of the plant buildings and facilities. The perimeter usually will coincide with the fence or property lines of the complex. The ambient so-interpreted includes the airspace, and surface- and ground-waters, beyond, above and below the perimeter ("outside-the-fence") of the complex., Ambient air monitoring. The major emphasis of ambient air monitoring should be in the measurement of unregulated air pollutants such as volatile and condensible organic compounds, trace metals, and radionuclides for which emission standards are not yet defined, but are potentially hazardous to health and biota. As the identity, release rate and release height of the individual pollutants are not known a priori, tentative criteria are given for selecting the number and location of the monitors which can be modified as experience is gained on collected pollutant quantities and instrument sensitivities., It is expected that most pollutants will emanate from low level (height) sources such as retorts, gasifier columns, sulfur recovery systems, liquid and solid waste disposal sites, and coal storage and handling systems. Ground-level pollutant concentrations will decline exponentially with distance because of horizontal and vertical diffusion. Multihour exposure may be necessary to collect a sufficient quantity of a pollutant for analysis. The meteorological factor having the greatest effect on the duration and frequency of sampling, and the location of the monitors, is the prevailing wind direction. Historical wind persistence analysis must be performed at each plant location to determine the wind sectors where the probability is greatest that multihour exposure will occur repeatedly over the monitoring period, say 1 year. It is proposed that monitors be placed in wind sectors where there is at least a 25% chance (100 days/year) that a collector be exposed to 6 or more hours per day (25%) of steady wind. If no single wind sector satisfies this requirement, monitors should be placed in several wind sectors such that at least 100 samples will have an exposure of 6 hours or more. The radial distance of the monitor should subtend an angle of 22.5 (one wind sector) with a cross section of the synfuel complex perpendicular to the monitor., Ambient water monitoring. The study involved an analysis of the behavior of organic effluents from a generic synthetic fuel plant in several representative environments. A generic approach was used because of the wide range of technologies used in synfuel development, and the variability of the aquatic environments which will receive their discharges. The approach was also necessary because there are no existing large-size synthetic fuel plants from which to obtain data. The analysis consisted of modeling the behavior of the effluents in generic environments. Specific compounds were chosen to represent broad classes of organic effluents. Also described are the schematizations of environmental processes used in the modeling., Modeling results indicate that there is not a unique monitoring site or frequency for all compounds in all environments. The optimal monitoring site is determined mainly by effluent chemistry, and the optimal frequency by environmental characteristics. The results presented here will be useful once an effluent stream and environment are specified. Environmental monitoring plans may then be compared for the appropriateness of the planned monitoring sites and adequacy of sampling frequency.