Risk of occupational allergy to stored grain arthropods and false pest-risk perception in Czech grain stores

Arthropods are a documented cause of occupational allergy in cereal stores. Since the current allergenic risk of various arthropods in grain stores is not known, we evaluated its extent using data from the Czech Republic (CZ). We surveyed 514 grain storage units for pest composition and density. Recalculating literature data we established 4 density dependent classes of pooled mite "allergy-risk level" (ARL) in stored grain: (i) safe-ARL: 0 mites.g(-1) grain, (ii) low-ARL: up to 1 mite.g(-1) grain, (iii) high-ARL: from 1 to 5 mites.g(-1) grain, (iv) danger-acute asthma-ARL: higher than 5 mites.g(-1) grain. Farmers (15) were questioned for pest taxon-related pesticide treatments. Mites constituted the largest group of collected pests (92%) followed by psocids (5%), beetles (3%) and moths (0%). 60% of mites belonged to known allergen producing species; the most abundant were Acarus siro, A. faris, Tyrophagus putrescentiae and Lepidoglyphus destructor. Grain samples belonged to the established ARL classes as follows: (i) safe-ARL: 37% (ii) low-ARL: 53%; (iii) high-ARL: 6%; (iv) danger-acute asthma-ARL: 4%. The enquiry among farmers revealed that almost no pesticides were targeted solely to control mites. This study suggests that mites represent, due to their allergenic potential, density and frequency, the most serious source of allergens in stored grain in CZ. However, the medical aspect of pest control--such as allergy avoidance strategy--is overlooked since grain feeding insects were mostly chemically controlled, regardless of their relatively low density and allergen production in comparison with mites.