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EPA-Expo-Box (A Toolbox for Exposure Assessors)

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Sources of contamination to air, water, and soil and dust are discussed in the Air, Water and Sediment, and Soil and Dust Modules in the Media Tool Set of EPA-Expo-Box. Media-specific concentrations are needed for estimating exposure via the inhalation route. Data tools that provide concentrations—or techniques for measuring or modeling concentrations—of contaminants in these media as well as Consumer Products are discussed in the media-specific modules and are also summarized in the subsequent sections.

Contamination of ambient (outdoor) air can occur from anthropogenic sources (e.g., driving cars, trucks, or buses; burning coal, oil, and other fossil fuels; manufacturing chemicals or other products; degreasing, painting, or other industrial operations; dry cleaning) or natural sources (e.g., gases emitted by the earth’s crust [e.g., radon]; smoke and carbon dioxide [CO2] released during forest fires). Activities such as these may add gases and/or particles to the air. Some air pollutants can remain in the environment for long periods of time and can be transported in the atmosphere (e.g., by wind) hundreds of miles from their original source.

There are many sources of indoor air contaminants. These contaminants can enter buildings from the outside or may be generated from inside sources (e.g., combustion of oil, gas, kerosene, coal, wood, and tobacco products; building materials and furnishings; consumer products). Reductions in building ventilation may increase indoor pollutant levels because indoor emissions are not being diluted by outdoor air or carried out of the indoor environment. Temperature and humidity can also contribute to increases in contaminant concentrations indoors.

Contaminant concentrations in air can be characterized based on measurements, modeling, and/or available monitoring data.

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Measuring Concentrations

Information on sampling techniques and analytical methods is available to support the measurement of contaminants in potentially inhaled media.

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Modeling Concentrations

In the absence of measurement data, a variety of models can be used to estimate contaminant concentrations in air or dust that may be inhaled. Ambient air quality models may be used to estimate contaminant concentrations in air considering spatial-temporal characteristics (e.g., urban versus rural, geographic scale; climate, season). Some models also account for population demographics and the time that the exposed populations spend in various microenvironments (see Factors tab of this module). Indoor air models and models that evaluate air concentrations for specific exposure scenarios (e.g., inhalation of contaminants that volatilize from water while showering, inhalation of contaminants that volatilize from pool water while swimming) are also available.

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Available Data

Personal or stationary monitors can be used to measure air concentrations in the breathing zone of individuals who are closest to a source. Area monitors may be used to measure air concentrations that are representative of particular areas. In some cases, measurement data are used directly to estimate exposure concentrations; in other cases, measured data are used along with modeling to predict potential levels of exposure.

There are a number of information sources that provide monitoring data on contaminant concentrations in potentially inhaled media. Many of these data sources provide ambient air concentrations of contaminants at the national level and for other broad geographic areas such as cities, counties, and states. As such, they help EPA identify specific air toxics, and specific source sectors such as stationary sources or mobile sources, that generally produce the highest exposures and risks.

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