Technology Transfer Network - Air Toxics Web Site
Health Effects Notebook
Health Effects Related Terms
Discussion of Related Terms Frequently Encountered
in Health, Exposure, and Risk Assessments
EXPOSURE COMPARED WITH DOSE
Exposure is the contact of a chemical with the outer boundary of a person, such as the skin, nose, or mouth. Exposure is measured as the concentration of the chemical multiplied by the time of contact. Thus, respiratory exposure is measured as ppm or g/m3 of the chemical in air multiplied by the hours or days of contact.
Dose is a general term which may be subdivided as follows: potential dose, applied dose, internal (asorbed) dose, and delivered dose. Potential dose is the amount of chemical contained in material ingested, air breathed, or bulk material applied to the skin, while the applied dose is the amount of the chemical in contact with the major absorption boundaries, such as the skin, lungs, and gastrointestinal tract, and available for absorption. The internal (absorbed) dose is the amount of a chemical penetrating across the absorption barrier. For the respiratory route, the internal dose is the amount of the chemical absorbed via the lung. The delivered dose is the amount of the chemical available for interaction with any particular organ or cell. All of these dose terms are measured as the mass of the chemical.
INDIVIDUAL RISK COMPARED WITH POPULATION RISK
Individual risk is that risk borne by individual persons within a population. When doing a risk assessment, frequently individual risks are calculated for some or all of the persons in the population being studied and then are put into the context of where they fall in the distribution of risks for the entire population. Population risk refers to an estimate of the extent of harm for a complete population, or for a segment of a population. In theory, an estimate of the extent of effects a population might incur can be calculated by summing the individual risks for all individuals within the population, or the population segment of interest.