This updated methodology recommends that risk assessors use the concentration of the contaminant in air (C air) as the exposure metric (e.g., mg/m 3) instead of the intake of a contaminant in air based on inhalation rate and body weight (dose e.g., mg/kg-day).Ĭ air = Concentration of contaminant in air (mg/m 3) This is described in Risk Assessment Guidance for Superfund (Part F, Supplemental Guidance for Inhalation Risk Assessment) (U.S. It has eliminated the use of inhalation rates when evaluating exposure to air contaminants. The Superfund Program has also recently updated its approach for determining inhalation risk. EPA report entitled Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry (U.S. The methods used in developing noncancer inhalation dose-response values for IRIS are discussed in more detail in the U.S. Instead, only an air concentration is needed to evaluate health concerns. This is because the IRIS methodology accounts for inhalation rates in the development of “dose-response” relationships. When using inhalation reference concentrations or inhalation unit risk from the Integrated Risk Information System (IRIS) to characterize risk, it is not necessary to calculate the inhaled dose. The anatomy and physiology of the respiratory system as well as the characteristics of the inhaled agent diminishes the pollutant concentration in inspired air (potential dose) such that the amount of a pollutant that actually enters the body through the upper respiratory tract (especially the nasal-pharyngeal and tracheo-bronchial regions) and lung (internal dose) is less than that measured at the boundary of the body. In the case of inhalation, the situation is complicated by the fact that oxygen exchange with carbon dioxide takes place in the distal portion of the lung. The Agency defines exposure as the chemical concentration at the boundary of the body (U.S. Exposure scenarios, exposure factors, and guidance for assessing exposure via inhalation are also provided. To calculate an inhaled dose, inhalation rates and receptor body weights might also be needed.Ĭalculations to estimate dose from inhalation are provided in this module as are various tools available for evaluating potential exposure concentrations. Indoor receptors could also be exposed to outdoor air contaminants that infiltrate the indoor environment.Įstimating exposure from inhalation requires information on the concentrations of contaminants in the air and the timeframe over which inhalation exposure occurs. Individuals can be exposed via the inhalation route during a variety of activities outdoors and indoors. Inhalation exposure can result from breathing air that is contaminated with particulate matter (e.g., dust), vapors (e.g., volatile or semivolatile contaminants), or aerosols. Typically, exposure occurs by one of three exposure routes-inhalation, ingestion, or dermal. is the way that a contaminant enters an individual or population after contact (IPCS, 2004). An exposure route exposure routeThe way a chemical pollutant enters an organism after contact, e.g., by ingestion, inhalation, or dermal absorption.
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