Ambient air particulates derived from a magnesite-processing plant contain magnesium oxide (85-90%), iron oxide (7-8%), calcium oxide (about 2.5-3%), Al- and Si oxides (0.1-0.5%) as well as additional elements in trace amounts as follows: Ni, Cr, Mn, Co, Hg, Cd, Pb, V, Ba, Ag, Cu and Sn. Magnesite clinker is manufactured from raw magnesite by baking in rotary furnaces using the Leseps-Polysius system, which represents the source of particulate pollutants entering the atmosphere. In the area heavily polluted by magnesite particles, the health impact using the data obtained from the exposed humans and animals was assessed. The reason for this study were the data on the increased frequency of respiratory diseases in children in the polluted area. In a group of children (9-10 years of age) residing in the area, the immune response to ambient air pollutants exposure in comparison to a non-exposed group living outside the polluted area was investigated. A statistically significant decrease in the amount of salivary lysozyme, SlgA, IgG and albumin in the exposed group was observed. Simultaneously, a 6-month respiratory exposure of a group of Chinchilla rabbits in that polluted area aimed at the simulation of the human exposure was conducted. In the exposed rabbits, enormously increased number of pulmonary alveolar macrophages (PAM) has been found. Using atomic absorption spectrometry, a statistically significant increase in magnesium content (e.g. a bioindicator of the exposure) in the body tissues of the exposed animals was found. The laboratory data obtained from the animal study contributed to the elucidation of the depressed immunity (especially in the respiratory system) in the children exposed to ambient air magnesite particulates.