Exposure to moulds and actinomycetes in Alpine farms: a nested environmental study of the PASTURE cohort.

Several studies have suggested that children exposed to a farm environment are protected against allergies and asthma. The present work is an environmental study nested within the PASTURE cohort and includes 97 farmers and 74 non-farmers in three regions of the Alpine Arc (Switzerland, France and Germany). The objectives were to determine and compare the fungi and actinomycetes present in farming and non-farming environments (children's bedrooms and cowsheds), and to identify the agricultural practices associated with an increase in airborne fungi and actinomycetes in cowsheds. Air samples were collected by air pump and were analysed by culture and by direct counting of spores on membranes. During their stay in bedrooms, children living on farms were exposed to significantly greater amounts of Absidia spp., Eurotium spp., Cladosporium spp., Penicillium spp. and mesophilic actinomycetes than children who did not live on farms. Depending on the season, the levels of moulds, yeasts and actinomycetes were from 14 to 82 times higher in cowsheds before feeding the cattle than in children's bedrooms, and from 12 to 464 times higher in cowsheds after feeding than in children's bedrooms. Feeding cattle in cowsheds was associated with a significant peak in airborne moulds and actinomycetes, and this peak was higher in winter than in summer. Silage distribution was associated with low amounts of moulds and actinomycetes. Other significant agricultural factors were the type of cowshed, cowshed volume, method of food distribution to cattle and use of fresh grass. An assessment of the microbiological diversity on farms and in children's rooms may help to determine the factors protecting children from asthma and atopic diseases.