Inhalant gases and vapors

Deposition of inhaled gases and vapors is modeled as a partitioning process that depends on the physiological parameters noted above as well as the solubility and reactivity of a compound in the respiratory tract (see Figure 3-3). The ICRP (1994b) model defines three categories of solubility and reactivity SR-0, SR-1, and SR-2 ... 

The absorption and retention of inhaled gases and vapors by the body are governed by certain factors different from those that apply to particulates. Solubility of the gas in the aqueous environment of the respiratory tract governs the depth to which a gas will penetrate in the respiratory tract. Thus very little if any of the inhaled, highly soluble ammonia or sulfur dioxide will reach the pulmonary alveoli, depending on concentration, whereas relatively little of insoluble ozone and carbon disulfide will be absorbed in the upper respiratory tract. 

Like the inhaled gases or vapors, soluble and insoluble aerosol particles can directly exert desirable and undesirable local effects at the site of deposition and/or systemic effects after solubilization, absorption, and metabolization. 

Finally, comparisons of various techniques for animal exposures indicate that the whole-body exposure technique is the most suitable for safety assessment of gases and vapors and permits simultaneous exposure of a large number of animals to the same concentration of a chug however, this technique is not suitable for aerosol and powder exposures because the exposure condition represents the resultant effects from inhalation, ingestion, and dermal absorption of the drug (Phalen, 1984 Gad and Chengelis, 1998). 

NiOSH REL (Waste Anesthetic Gases and Vapors) CL 2 ppm/lH SAFETY PROFILE Mildly toxic by inhalation, ingestion, and subcutaneous routes. Human systemic effects by inhalation decreased urine volume or anuria. An experimental teratogen. Experimental reproductive effects. Human mutation data reported. An eye irritant. Questionable carcinogen with experimental carcinogenic data. An anesthetic. When heated to decomposition it emits ver " toxic fumes of F and Cl . See also ETHERS. 

LC50 (lethal concentration 50%). That quantity of a substance administered by inhalation that is necessary to kill 50% of test animals exposed to it within a specified time. The test applies not only to gases and vapors but to fumes, dusts, and other particulates suspended in air. 

One of the constant concerns of numerous industries where either aerosols or toxic vapors are produced is the effects of these upon workers. A variety of health problems arise because of the workers inhaling gases and aerosols of irritant or toxic fibers which are produced in the normal course of activities. A less obvious hazard arises from the attachment of trace molecular species to particles. If these trace species are radioactive or chemically toxic, the particles, which effectively concentrate them, provide a vehicle for delivery deep within the body causing a health hazard far beyond that suggested by their gross molecular concentration in the air [1.31,32]. Kinetic theory, thermodynamics, and interaction forces, all enter into descriptions of the attachment process. 

Airborne particulates, gases, and vapors that are capable of causing illness or injury to workers upon ingestion, inhalation, or skin or mucous membrane contact. 

Although gases and vapors will move freely with inhaled air, particulates may behave differently. Because of their mass or shape, larger particulates (generally those greater than 5-7 pm in diameter) will not make sharp turns... 

If metals and metal compounds are inhaled, water-soluble gases and vapors are readily dissolved in the mucous membranes of the nasopharyngeal and tracheobronchial region. Less soluble gases and vapors reach the terminal airways and the alveoli and then may pass into the bloodstream or lymph stream. Deposition of inhaled particles in the airways mainly occurs by impaction, sedimentation, and diffusion. 

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