Science and Judgment in Risk Assessment (1994) / Chapter Skim
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Appendix C: Calculation and Modeling of Exposure
Appendix C: Calculation and Modeling of Exposure
Pages 375-382
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From page 375... ...
and the duration of contact with a person or population. If the concentration of a pollutant to which a person is exposed can be measured or modeled and the time spent in contact with the pollutant is known, exposure is determined from concentration and time.
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From page 376... ...
j=1 j=1 The latter equation includes the totality of all locations and activities that the person can occupy and engage in. To obtain the total exposure of a population Epop of N persons, it is necessary to sum the individual exposures Ei of all the persons in the population from i = 1 to N: N N M Epop = >, Ei = I, I, Cj~tij Generally, the amount of time spent in each microenvironment is averaged over the exposed population, M Epop = NO Cj /\ t j=1 so that the average population exposure is given by Epop=~ j=1 Thus, it is necessary to estimate the atmospheric concentration of the pollutant to which people are exposed to obtain Cj and their activity patterns to obtain AtJ MODELING OF EXPOSURE It is often impossible or impractical to measure the exposures of individuals or populations directly, and instead mathematical models are used to estimate exposures.
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From page 377... ...
They have also been designed for various temporal averaging periods. A number of Gaussian-plume models, with individual names, correspond to the various mathematical formulations used in the models.
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From page 378... ...
The model was then compared with the standard UNIMAP models issued by the EPA Office of Air Quality, Planning, and Standards as part of the National Ambient Air Quality Standards (NAAQS) State Implementation Plan process, and it was found that they generally agreed to within a factor of 3.
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From page 379... ...
and to evaluate mitigation strategies for indoor exposures to selected pollutants for five scenarios, such as exposure to CO from a gas boiler in a school (Eisinger and Austin, 1987~. Simulation of Human Air Pollution Exposure (SHAPE)
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From page 380... ...
The total exposure is therefore estimated as the exposure due to local sources plus the ambient concentration at the background site. For each person in the hypothetical sample, the model generates a profile of activities and pollutant concentrations attributable to local sources over a given period, such as a 24-hour period.
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From page 381... ...
U.S. Environmental Protection Agency, Research Triangle Park, N.C.
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From page 382... ...
Environmental Protection Agency, Research Triangle Park, N.C. Russell, A.G.
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