Lung disease in farmers.

Lung diseases in farmers attributable to their occupation include (a) farmer's lung, caused by exposure to mouldy hay, (b) the asthma caused by exposure to grain dust and (c) silo-filler's disease. Their prevalence in Canada is unknown. Farmer's lung results from inhalation of mould spores in hay; the mechanism is immunologic. The exact cause and mechanism of grain dust asthma are unknown but may be immunologic. Silo-filler's disease is caused by the toxic effects of inhaled nitrogen dioxide.