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Chronic combined exposure to low concentrations of chemical substances (equal to the maximal admissible limits for space vehicles) is fraught with an increase in chromosomal aberrations in bone marrow cells as compared with the spontaneous chromosome aberration rate. In addition to the cytogenetic evidence, there were also statistical phase shifts in metabolic parameters of erythrocytes (enzymes involved in the basal metabolism and a number of metabolites), leukocyte count in peripheral blood, and the total quantity of karyocytes in the bone marrow. No significant changes were found in organs of the immune and reproductive systems.

Based on the multiyear experience of hygienic control of the orbital stations, there are three causes of contingent air pollution: leakage of service system pipeline with chemical working bodies, spills of reagents used in biochemical and technological experiments, and air pollution by products of thermal oxidative degradation of nonmetallic materials. The authors describe their experience in successful elimination and prevention of hazardous consequences of fire aboard the space stations. Analysis of air pollution dynamics after actual fire events in the space station modules showed that it approximates a two-chamber air flow model with two phases of pollutant equilibration: first a rapid fall of concentration in the module on fire till air in the modules gets completely mixed, and then slow elimination of harmful pollutant from air. Identified were markers,--propylene and methylmetacrilate,--reacting to first signs of fire. Carbonic acid nitriles were recognized as toxic products of destruction. The positive effect of intermodular ventilation on dilution of toxic products of thermal oxidative destruction of materials was demonstrated. Satisfactory agreement of calculated and factual pollutant concentrations on board Mir permitted conclusion on applicability of the theoretical model to prediction of levels of air pollution due to contingency.

The purpose of the study was to investigate adaptive responses of the human body to chemicals of anthropogenic origin in an enclosed environment. The object of the study was ammonia, a typical metabolite and a permanent contaminant of a enclosed atmosphere. The study consisted of a prolonged and continuous exposure to ammonia at a concentration of 2.0 +/- 0.1 mg/m3 and a 24-hour exposure to ammonia at a concentration of 9.8 +/- 0.1 mg/m3. The results showed that ammonia was neutralized in a stage-by-stage manner. At first the anthropotoxin was eliminated in exhaled air. As the exposure continued, additional mechanisms became involved, i.e. ammonia binding and renal excretion. Activation of ammonia detoxication occurred without noticeable involvement of the sympathoadrenal system.