PMC:1247194 / 37204-38963 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":"A key issue in exposure assessment is how well an exposure metric estimates exposure to the individual. Exposure has been defined as “the contact of a chemical, physical, or biological agent with the outer boundary of an organism” (Berglund et al. 2002). Exposure is a function of concentration and time: “An event that occurs when there is contact at a boundary between a human and the environment with a contaminant of a specific concentration for an interval of time” (NRC 1991). Thus, in the context of exposure assessment for an epidemiologic study, it is important to distinguish between environmental concentration, exposure concentration, and dose. The environmental concentration of an agent refers to its presence in a particular carrier medium [for example, polycyclic aromatic hydrocarbons (PAH) in ambient air], expressed in quantitative terms (for example, micrograms per cubic meter). Similarly, the exposure concentration of an agent refers to its presence in its carrier medium at the point of contact (for example, PAH in breathing zone air) expressed in quantitative terms (for example, micrograms per cubic meter). Finally, the dose refers to the amount of a pollutant that actually enters the human body, i.e., is taken up through absorption barriers. A number of variables can influence the exposure and dose. These include physiologic factors such as age, sex, physical condition, disease, and genetics, as well as exposure factors related to human behavior and activities (e.g., the amount of time spent commuting to work each day), and contact rates (e.g., the amount of drinking water ingested per day). In epidemiologic studies, environmental concentration will often be used as a surrogate for both exposure concentration and dose.","tracks":[]}