PMC:1247194 / 32727-34096 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/1247194","sourcedb":"PMC","sourceid":"1247194","source_url":"https://www.ncbi.nlm.nih.gov/pmc/1247194","text":"Exposure is a function of the concentration of target contaminant in the environment of the study population. The optimal method for quantifying levels of the target agent is the measurement of the environmental media associated with each potential route of exposure during the critical time period for exposure. However, rarely is there an opportunity to make such measurements. Alternatively, predicted environmental levels of the target agent can be estimated using source-receptor modeling. Computer-based models designed to predict levels of contaminants due to point sources (smokestack) or nonpoint sources (drift from aerial spraying of pesticides) are available. Often these predictions are used as a surrogate for exposure in the epidemiologic analysis. In either case, validation of the estimates is important to understand the results of the epidemiologic study. Validation is often overlooked in the exposure assessment process. It is also important that the environment depicted in the modeling period be representative of the environment during the exposure period necessary for the epidemiologic study. Generally, the degree to which validation can be accomplished is a function of measurement data available for the time period of interest. Most source-receptor models require some measurements for constructing (calibrating) the predictive algorithms.","tracks":[]}