A vast number of compounds produce irritant effects when inhaled in the gaseous form. The most common source of exposure to irritant gases is industry, but significant exposures may occur in a variety of circumstances, such as after mixing cleaning agents at home, with smoke inhalation in structural fires, or after highway tanker spills.
MECHANISM OF TOXICITY
Irritant gases often are divided into two major groups on the basis of their water solubility (Table II–31).
Highly soluble gases (eg, ammonia and chlorine) are readily adsorbed by the upper respiratory tract and rapidly produce their primary effects on moist mucous membranes in the eyes, nose, and throat.
Less soluble gases (eg, phosgene and nitrogen dioxide) are not rapidly adsorbed by the upper respiratory tract and can be inhaled deeply into the lower respiratory tract to produce delayed-onset pulmonary toxicity.
The toxic dose varies with the properties of the gas. Table II–31 illustrates the workplace exposure limits (TLV-TWA) and the levels immediately dangerous to life or health (IDLH) for several common irritant gases.
Table Graphic Jump Location TABLE II–31.IRRITANT TOXIC GASES ||Download (.pdf) TABLE II–31. IRRITANT TOXIC GASES
|Gas ||TLVa (ppm) ||IDLHb (ppm) |
|High water solubility || || |
| Ammonia ||25 ||300 |
| Chloraminec ||N/A ||N/A |
| Formaldehyde ||0.3(C) ||20 |
| Hydrogen chloride ||2(C) ||50 |
| Hydrogen fluoride ||2(C) ||30 |
| Nitric acid ||2 ||25 |
| Sulfur dioxide ||0.25(S) ||100 |
|Moderate water solubility || || |
| Acrolein ||0.1(C) ||2 |
| Chlorine ||0.5 ||10 |
| Fluorine ||1 ||25 |
|Low water solubility || || |
| Nitric oxide ||25 ||100 |
| Nitrogen dioxide ||3 ||20 |
| Ozone ||0.2d ||5 |
| Phosgene ||0.1 ||2 |
All these gases may produce irritant effects in the upper and/or lower respiratory tract, but warning properties and the onset and location of primary symptoms depend largely on the water solubility of the gas and the concentration of exposure.
Highly soluble gases. Because of the good warning properties (upper respiratory tract irritation) of highly soluble gases, voluntary prolonged exposure to even low concentrations is unlikely.
Low-level exposure causes rapid onset of mucous membrane and upper respiratory tract irritation; ...