Introduction
This note covers occupational intoxication with nitrogen oxides, mainly nitrogen dioxide (NO_2) and nitric oxide (NO). It explains where workers are exposed, how the gases damage the lower airways, how acute and chronic poisoning present, how the condition is diagnosed and treated, and what medical expertise requires.
Etiology and sources of exposure
Nitrogen oxides are formed whenever nitrogen and oxygen are combined at high temperature or when nitrogen-containing compounds are oxidised. The main occupational sources are:
- production, storage and transport of nitric acid, and its use in fertilizer manufacture
- nitration processes in the manufacture of explosives, dyes, adhesives and some medicinal substances
- fuel combustion, including diesel and petrol engine exhaust in closed spaces, and arc and gas welding
- gas and kerosene appliances used without adequate ventilation
- fermenting silage in silos, the classic cause of acute exposure in farm workers, and nitrogen gases released during blasting in mines
High-risk occupations include farmers and silo fillers, firefighters, arc welders, miners, workers in nitric acid and fertilizer plants, and traffic officers exposed to vehicle exhaust. Acute episodes often follow an accident, a sudden release or work in a poorly ventilated space, while chronic poisoning develops from repeated low-level exposure over years.