Inhalation is the most common exposure route in reports to national
poison control centers and the most common cause of fatalities related
to toxic exposures. Acute inhalational injury occurs via two basic
mechanisms. Inhaled substances are either absorbed leading to systemic
toxicity or they directly injure the pulmonary epithelium at various
levels of the respiratory tract. Many exposures (or exposure situations)
produce both effects. Systemic toxins include asphyxiants (substances that
interfere with oxygen delivery or utilization) and other toxins
whose primary effects are on distant organ systems. This chapter
will not discuss inhalational toxins whose main effects are on distant
organ systems but limited examples are shown in Table 35–1.
Table 35–1. Systemic
Toxins Absorbed Via Inhalation. |Favorite Table|Download (.pdf)
Table 35–1. Systemic
Toxins Absorbed Via Inhalation.
|Agent||Exposure Scenarios||Systemic Effects|
|Arsine||Chemical industry, smelting, and refining; semiconductor industry;
metal pickling and plating||Massive intravascular hemolysis leading to jaundice, hemoglobinuria,
and renal failure; also causes pulmonary edema|
|Solvents||Extensive use in industry and in the home environment (mechanic
work)||Central nervous system (CNS) intoxication, similar to alcohol;
hepatic damage may occur with heavy exposure to chlorinated solvents|
|Benzene||Chemical, detergent, pesticide, and solvent manufacture||CNS toxicity, bone marrow suppression; long-term exposure
causes hematological malignancy|
|Nerve gas||Chemical weapons, terrorism||Paralysis, cholinergic crisis (bradycardia, excessive secretions,
|Pesticides||Gardening, farm work||Depends on the agent; organophosphates are similar to nerve
The degree of injury after acute inhalational exposure is determined
by multiple host and exposure factors. Elderly patients and those
with underlying debilitating illness, particularly underlying lung
disease that impairs host defense mechanisms, typically fare worse.
Important environmental factors include the intensity and duration
of exposure as well as the quality of ventilation in the space in
which exposure occurs. In general, greater exposure dose (defined
as the product of the concentration of exposure and duration of
exposure) is associated with greater potential harm.
- • Patients may be unaware of asphyxiant exposure,
as many do not have warning properties.
- • Consider asphyxiants in patients with a history
of working in enclosed spaces prior to symptom onset.
- • Consider asphyxiant exposure in patients with a
history of smoke inhalation.
- • Consider chemical asphyxiant exposure in patients
with unexplained lactic acidosis.
Asphyxiants are divided into two classes, simple and chemical.
Simple asphyxiants act by displacing oxygen from inspired air. Any
gas can act as a simple asphyxiant if present in high enough concentration.
Typical exposure scenarios include release of compressed gas and
work in enclosed spaces. Chemical asphyxiants act by interfering
with oxygen delivery or utilization. Examples of both simple and
chemical asphyxiants are shown in Table 35–2.
The potential number of exposed workers in the United States is
unclear, but the National Occupational Exposure Survey estimated
that more than 500,000 workers may ...