Chamber and field dust pollution monitoring on laboratory rats and rabbits was used for evaluating the effect of magnesite and cement industrial dust on alveolar ma rophages. Animals were exposed for 6 months to magnesite emissions and for 20 months to cement emissions in a biomonitory station near magnesite or cement works, respectively. The control animals were kept in an area free of dust pollution. After finishing the exposure alveolar macrophages were isolated and acid phosphatase and .beta.-glucuronidase activities were assayed. In the exposed animals the activity of studied enzymes was enhanced significantly. The results of chamber exposure to the magnesite dust (lasting for 9 or 14 weeks) were fully in agreement with those of field experiments. The findings point to the fact, that in spite of the low dust pollution level in the field experiments, the AM lysosomal enzyme activities have been nonspecifically stimulated.