The investigators studied the impact of biological air contamination by the dusts resulting from protein feedstuff manufacture and grain on local immunity of the mucosae in children and adults living in the areas that were differently distant from industrial objects, the sources of contamination, as well as in workers of the shops contaminated by dust containing various amounts of protein. The studies showed that the workers of a biochemical plant exhibited a considerable change in the majority of immunological parameters (lysozyme activity, heterophile antibody titers, salivary and skin bactericidity, salivary total and R-protein, and immunoglobulins A, M, G, and E). There was a significant decrease in salivary IgA activity. The immunological parameters of children and adults were further compared with their morbidity as the most important health index. It was found that with the production rates being steadily raised, the average annual morbidity increment was 1.3; children less than 14 years of age in whom the incidence of bronchial asthma and bronchitis with asthmatic components increased 5-fold were most susceptible.