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The lungs and airways are in constant contact with the outside world and thus, are especially vulnerable to toxic substances present in the environment. Within seconds of exposure to an inhaled toxin, pathologic events occur that may cause immediate distress, systemic illness lasting days, or even lead to the development of chronic lung disease. This chapter discusses the pathology and pathophysiology that can result from various inhaled toxins, and also highlights the role of several common and medically significant toxic inhalants that are known to cause acute and chronic pathophysiologic responses in the lung. The chapter also discusses several systemic syndromes caused by acute toxic inhalations. The scope of this chapter does not include chronic exposure to low levels of toxins.

Determinants and Mechanisms of Irritant-Induced Pulmonary Injury

Inhaled toxins exist in many forms and may be categorized by taking into account their physical properties. General categories include gases, vapors, fumes, aerosols, and smoke. A variety of factors determine the pathologic results of a toxic inhalation: the size of inhaled particles, the solubility of the inhaled substance in water, the concentration of the inhalant in ambient air, the duration of exposure, the presence or absence of ventilation, and a variety of host factors (age, smoking status, comorbid diseases, use of respiratory protection, and perhaps even genetic susceptibility). While toxic inhalants provoke a broad range of chemical and biologic activities that contribute to pathogenesis, their physical properties, namely their particle size and water solubility, are of fundamental importance in determining the site and severity of pulmonary injury. Tables 90-1 to 90-3 summarizes the physical properties of the discussed inhalants that substantially affect the resulting pathogenesis of these agents.

Table 90-1Definitions of Types of Inhaled Substances
Table 90-2Water Solubility and Mechanisms of Lung Injury of Gaseous ...

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