Environmental allergen exposure and asthma: prospects for primary prevention.

ture in homes (frequent showers, new cooking methods, inadequate airing of bedrooms, etc.). From 1981 to 2000, the Scientific Institute of Public Health sampled more than 500 home environments of allergic and/or asthmatic patients in urban or rural areas throughout Belgium. Results showed that more than 150 fungal species, among them Cladosporium, Penicillium and Aspergillus, were collected in 90–98% of the sampled environments. Cladosporium sphaerospermum was found in 60% of the dwellings, with the highest levels of contamination especially in bedrooms and bathrooms (hundreds of spores/m ). C. sphaerospermum is often associated with Aureobasidium pullulans, Phoma sp., Acremonium strictum and some yeast on window frames, whereas Cladosporium herbarum, which is an outdoor mould, does not grow in dwellings. However, its spores invade home environments through open doors and windows, mainly during the summer months. Aspergillus versicolor, Penicillium chrysogenum, Penicillium aurantiogriseum, Penicillium spinulosum, Penicillium brevicompactum, Chaetomium globosum, Stachybotrys chartarum, A. strictum and Alternaria alternata are sometimes found in huge quantities on walls in bedrooms, living rooms and kitchens, most frequently inducing allergic asthma. Mattresses are also often badly looked after, and the concentrations of dust are often quite important: 10 –10 spores/g of dust. In temperate regions, moulds, like mites, are thriving in environments that are excessively moist because of a lack of ventilation and new living conditions. In tropical zones, the conditions that stimulate the growth of moulds are found naturally. Among the most frequent species, C. sphaerospermum, A. alternata, Epicoccum purpurescens, A. pullulans, Aspergillus restrictus and A. versicolor, various species of Mucorales and Trichoderma should be pointed out. Mould strips due to C. sphaerospermum can even sometimes be seen at contact point of mattresses and fixed bedslats. It should also be noted that some Basidiomycetes grow mainly in enclosed spaces. Serpula lacrymans or Merulus lacrymans is the dreadful dry rot responsible for considerable damage in dwellings. This fungus attacks damp wood and can very rapidly grow across timber and even walls. It only develops in enclosed spaces. For about 20 years now, lack of ventilation in present dwellings has made this fungus active again, and cases of sensitization have been diagnosed. Mycotoxins associated with moulds are secondary metabolites with low molecular weight compared with allergens. It is well known that ingestion of mycotoxins (ex. aflatoxins) can cause illness and even prove fatal for Man. According to various studies, it has been established now that inhalation of the same amounts of mycotoxins is even more toxic. Trichothecenes produced by S. chartarum and various Fusarium spp., patulin, and penicillic acid produced by various Penicillium have shown acute toxicity. Large areas contaminated by S. chartarum and A. versicolor can sometimes be seen on damp walls in dwellings. Great care should thus be exercised with patients living in ‘musty’ dwellings and complaining of irritation symptoms and nausea when at home. B1–3 glucans, components of the walls of moulds, act as potent inflammatory agents. Their role as asthma exacerbator in musty homes should not be neglected. In summary, moulds are linked at different stages to allergic reactions and more especially asthma: