Respiratory disease of workers harvesting grain

The incidence of respiratory symptoms caused by grain dust during harvesting was surveyed in a group of Lincolnshire farmers. A quarter complained of respiratory distress after working on combine harvesters or near grain driers and elevators, with cough, wheezing, and breathlessness, sometimes so severe as to prevent work. The airborne dust around combine harvesters contained up to 200 million fungus spores/m3 air with Cladosporium predominant while drivers were exposed to up to 20 million spores/m3 air. Verticillium/Paecilomyces type spores, mostly from Verticillium lecanii, Aphanocladium album, and Paecilomyces bacillosporus, were abundant in the dust. Extracts of these species produced immediate weal reactions in skin tests, precipitin reactions with sera, and rapid decreases in FEV1 when inhaled by affected workers. There was no delayed reactions. Results suggest type I immediate hypersensitivity to the spores although the physical effect of a heavy dust deposit could be important. Drivers could be protected by cabs ventilated with filtered air.