Potentially hazardous substances may be encountered as airborne toxicants across occupational, vocational, indoor environmental, and ambient exposure scenarios. These substances can exist in one or more of several physicochemical states, including gases, fumes, mists, aerosols, vapors, and smoke. Table 33–1 lists common definitions of these terms. The physicochemical distinctions among categories of airborne toxicants are of limited clinical application, but may be relevant for industrial hygiene monitoring and in interpreting workplace exposure limits. Airborne toxicants cause respiratory tract injury and/or systemic injury beyond local effects on the airways or lungs. Either group of toxic responses can be mediated through a wide variety of mechanisms.
Table 33–1.Definition of terms. ||Download (.pdf) Table 33–1. Definition of terms.
|Aerosol ||A dispersion of solid or liquid particles in a gaseous medium, most commonly air. |
|Gas ||A fluid at room temperature and pressure that occupies the space of enclosure; capable of being changed into the solid or liquid phase by both an increase in pressure and a decrease in temperature. |
|Vapor ||The gaseous phase of a substance normally in the solid or liquid state; capable of being changed to liquid or solid either by increasing pressure or decreasing temperature. |
|Mist ||An aerosol of liquid particles that may be visible and is generated by condensation from the gaseous to liquid state or by mechanical dispersion of a liquid. |
|Fume ||An aerosol of solid particles generated by the condensation of vaporized materials, especially molten metals, often accompanied by oxidation. |
|Dust ||Solid particles generated by disintegration of organic or inorganic materials such as rocks and minerals, wood and grain; capable of temporary suspension in a gaseous medium such as air. |
|Smoke ||Aerosols of solids resulting from incomplete combustion. |
Victims of airborne toxicant exposure may be evaluated and treated across a professional mix of health care providers, including occupational physician or nurse specialists, primary outpatient or inpatient providers, or various subspecialists such as pulmonologists or allergists. Victims of high-intensity exposures are more likely to be managed initially by first responders (eg, paramedics, firefighters, or integrated hazmat teams) and subsequently by emergency department physicians and nurses. Other disciplines (eg, toxicology, otolaryngology, speech therapy, psychiatry, and neurology) may also become involved in the assessment and care of airborne toxicant associated illness depending on the nature of the exposure, the acuity of the presentation, the constellation of signs and symptoms involved, and forensic or medico-legal considerations.
ROUTE OF EXPOSURE & TARGET ORGAN TOXICITY
The respiratory tract may be the toxicant's route of exposure, the toxicant's target organ for injury, or both. All of the toxicants discussed in this chapter enter the body principally, if not exclusively, through inhalation (although there are uncommon scenarios where lung injury can occur through ingestion of certain substances not covered here, such as the herbicide paraquat). In addition to being the primary route of exposure, the ...