Is ammonia toxic?

Inhalation of large amounts of ammonia gas over a short period can cause swelling and pain in the throat. However, some people believe ammonia is non-toxic. Is ammonia actually toxic?

Is ammonia toxic?

Yes, ammonia is toxic. Ammonia primarily causes toxicity via inhalation through the respiratory tract. Its toxicity to humans depends on both the concentration of ammonia in the environment and the duration of exposure. Low concentrations of ammonia irritate mucosal surfaces, whereas high concentrations induce tissue protein denaturation and saponification of fatty tissues—termed “saponification”—leading to liquefactive necrosis. This results in chemical inflammation of the skin and upper respiratory mucosa, as well as burns, pulmonary congestion, pulmonary edema, and hemorrhage. Most inhaled ammonia that reaches the alveoli is absorbed into the bloodstream, elevating blood ammonia levels and causing damage to the central nervous system—initially manifesting as excitation, followed by paralysis. Ammonia may also induce hepatic fatty degeneration, renal interstitial inflammatory changes, and myocardial injury.

Mild ammonia poisoning manifests radiographically as enhanced or blurred pulmonary markings, consistent with bronchitis or peribronchitis; arterial blood gas analysis typically reveals a partial pressure of oxygen (PaO₂) lower than expected. Moderate poisoning shows thickened, indistinct, or reticular pulmonary markings, reduced lung transparency, and scattered patchy opacities with ill-defined margins—findings consistent with pneumonia or interstitial pneumonia.

When the arterial PaO₂ remains above 60 mmHg, the ammonia concentration is generally below 50%. Severe poisoning is characterized by ill-defined patchy opacities and diffuse, hazy opacities throughout both lung fields, which may coalesce extensively. We hope this information is helpful to you.