Ammonia is widely used as a refrigerant, a fertilizer, and a household and commercial cleaning agent. Anhydrous ammonia (NH3) is a highly irritating gas that is very water-soluble. It is also a key ingredient in the illicit production of methamphetamine. Aqueous solutions of ammonia may be strongly alkaline, depending on the concentration. Solutions for household use are usually 5–10% ammonia, but commercial solutions may be 25–30% or more. The addition of ammonia to chlorine or hypochlorite solutions will produce chloramine gas, an irritant with properties similar to those of chlorine (See Chlorine).
Mechanism of toxicity. Ammonia gas is highly water-soluble and rapidly produces an alkaline corrosive effect on contact with moist tissues, such as those of the eyes and upper respiratory tract. Exposure to aqueous solutions causes corrosive alkaline injury to the eyes, skin, or GI tract (see “Caustic and Corrosive Agents”).
Ammonia gas. The odor of ammonia is detectable at 3–5 ppm, and persons without protective gear will experience respiratory irritation at 50 ppm and usually self-evacuate the area. Eye irritation is common at 100 ppm. The workplace recommended exposure limit (ACGIH TLV-TWA) for anhydrous ammonia gas is 25 ppm as an 8-hour time-weighted average, and the OHSA permissible exposure limit (PEL) as an 8-hour time-weighted average is 50 ppm. The level considered immediately dangerous to life or health (IDLH) is 300 ppm. The Emergency Response Planning Guidelines (ERPG) suggest that 25 ppm will cause no more than mild, transient health effects for exposures of up to 1 hour.
Aqueous solutions. Diluted aqueous solutions of ammonia (eg, <5%) rarely cause serious burns but are moderately irritating. More concentrated industrial cleaners (eg, 25–30% ammonia) are much more likely to cause serious corrosive injury.
Clinical presentation. Clinical manifestations depend on the physical state and route of exposure.
Inhalation of ammonia gas. Symptoms are rapid in onset owing to the high water solubility of ammonia and include immediate burning of the eyes, nose, and throat, accompanied by coughing. With serious exposure, swelling of the upper airway may rapidly cause airway obstruction, preceded by croupy cough, hoarseness, and stridor. Bronchospasm with wheezing may occur. Massive inhalational exposure may cause noncardiogenic pulmonary edema.
Ingestion of aqueous solutions. Immediate burning in the mouth and throat is common. With more concentrated solutions, serious esophageal and gastric burns are possible, and victims may have dysphagia, drooling, and severe throat, chest, and abdominal pain. Hematemesis and perforation of the esophagus or stomach may occur. The absence of oral burns does not rule out significant esophageal or gastric injury.
Skin or eye contact with gas or solution. Serious alkaline corrosive burns may occur.
Diagnosis is based on a history of exposure and description of the typical ammonia smell, accompanied by typical irritative or corrosive effects on the eyes, skin, and upper respiratory or GI tract.
Specific levels. Blood ammonia levels may be elevated (normal, 8–33 mcmol/L) but are not predictive of toxicity. Testing should be performed on a stat basis because ammonia levels increase after blood collection owing to the breakdown of proteins.
Other useful laboratory studies may include electrolytes, arterial ...