Volatile toxicants, exposure, evaluation

Evaluating Exposures to Volatile Toxicants by Monitoring Evaluation of Worker Exposures to Dusts 83 Evaluating Worker Exposures to Noise 84 Estimating Worker Exposures to Toxic Vapors 85... 

Kinetics Considerations. Kinetics concepts and data concerning halocarbon sources and sinks can be used for a variety of purposes. For example, such information is required in mathematical models to evaluate the fate and exposure concentrations of low-volatility toxic organohalogens in water (18, 19). Moreover, kinetics relationships and data concerning physical, chemical, and biological processes are needed to predictively model aquatic sinks of volatile halocarbons (11). 

In the evaluation of toxic characteristics of an inhalable environmental chemical (e.g., carbon monoxide, volatile chemical, or aerosol/particulate), determination of acute inhalation toxicity is an initial study step. It provides information on health hazards likely to arise from short-term exposure by inhalation. Data from an acute test help to establish a dose regimen in subchronic (and other) studies, and may provide additional information on a chemical s mode of toxic action. 

For evaluating the toxic characteristics of an inhalable material (e.g., gas, volatile chemical, or aerosol/particulate material), animals are subjected to repeated exposures after initial information on material toxicity has been obtained by acute testing. It provides information on health hazards likely to arise from repeated exposure via the inhalation route over a limited period of time. Hazards of inhaled chemicals are influenced by inherent toxicity and physical factors, such as volatility and particulate size. 

Toxicity of chemicals can be expressed in terms of IDLH (immediate danger to life and health) level, LCtso, REL (recommended exposure limit) and PEL (permissible exposure limit), and AEL (acceptable exposure Umit), among others. Physical and chenucal properties have direct influence on the behavior of a compound. For example, a vapor or liquid with high vapor pressure would create a respiratory inhalation hazard as the primary threat. Solids or low-volatility liquids may not produce a sufficieutly concentrated vapor to act as an inhalation threat. Their primary threat would be through direct contact. Specific hazards will dictate respective detection and evaluation methodologies. 

Work is continuing in the area of vapor intrusion, and hopefully the level of precision in modeling will increase as we learn more about how specific vapors move through the subsurface environment and foundation cracks and wall seams. Given that several volatile chemicals are more toxic when inhaled than ingested (e.g., chloroform, toluene, methylene chloride, hexane, hydrogen cyanide, chlorine, methyl isobutyl ketone, naphthalene), rigorous and accurate evaluation of this potential exposure pathway is critical to adequately protect human health. 

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