Near death due to inhalation of slurry tank gases.

Slurry tank storage facilities are playing an increasing role in mechanised farming. Accidental poisoning from gases produced in such tanks is a recognised hazard, and multiple fatalities have been reported.1 2 The principal constituents are methane, ammonia, carbon dioxide and hydrogen sulphide. The most dangerous of these is hydrogen sulphide which acts in a similar manner to cyanide, with reversible inhibition of the respiratory enzyme cytochrome oxidase. Concentrations above 200 parts per million (ppm) produce direct irritant effects on exposed surfaces, and pulmonary oedema on prolonged inhalation.3 Higher levels (above 500 ppm) depress the central nervous system, with paralysis of the respiratory centre, and almost instantaneous loss of consciousness. The familiar smell of 'rotten eggs' is not a reliable warning sign as paralysis of the olfactory nerve makes the gas odourless at lethal levels. Most reported cases have been associated with agitation of slurry prior to, or during, emptying procedures, although toxic exposure to hydrogen sulphide can also occur in sewers, mines and the chemical industry. The problem was exacerbated in 1985 by the wet summer and autumn, which made fields unworkable. Large quantities of slurry therefore remained undisturbed for long periods and subsequently more gas than usual accumulated beneath a hard crust, to be released when the tanks were eventually emptied. CASE HISTORY A 31-year-old farm labourer, previously in good health, was preparing to empty a tank containing approximately 6,000 gallons of slurry. This had been undisturbed since the autumn one year previously. The surface crust had been broken and the contents agitated by a tractor-driven mechanical pump prior to removal to a tanker. His workmates noticed him slumped over the drainage slats above the slurry tank inside the cowshed. Help was summoned and he was dragged outside within three minutes. The patient was noticed to be blue, pulseless and unconscious, with very weak respiratory efforts only. No attempts at cardiopulmonary resuscitation were made. Two cows in the cowshed died immediately and a calf was later destroyed.