Toxicological and hygienic assessment of calcium dinitrate: justification of the maximum permissible concentration in the air of the working area

Introduction. The article tells about the widespread use of calcium nitrate (calcium nitrate, anhydrous calcium nitrate, calcium salt of nitric acid), about the use in the production of additives to concrete, deicing reagents, detergents, fertilizers and in other fields of human activity. There are data in the literature on the toxicity and danger of compounds similar in chemical structure, there is an approved maximum permissible concentration of calcium dinitrate in the atmospheric air of urban and rural settlements equal to 0.03 mg/m3 — the maximum single and 0.01 mg/m3 — the average daily in accordance with SanPiN 1.2.3685-21. However, the hygienic standard of calcium dinitrate in the air of the working area, which is necessary to ensure the preservation of the health of workers, has not yet been established. The study aims are the hygienic rationing of calcium dinitrate in the air of the working area based on the study of the toxic properties and nature of the biological action of the substance in various ways of entry into the body of experimental animals. Materials and methods. The authors had carried out experimental studies on non-harmless white rats of both sexes of the Wistar line, non-harmless white mice, white Agouti guinea pigs, rabbits of the Soviet Chinchilla breed in single and repeated experiments with oral, inhalation and percutaneous exposure. Experts have assessed the condition of experimental rats after a single inhalation exposure to calcium dinitrate at concentrations of 102.1±6.2 mg/m3 and 35.3±5.1 mg/m3 by changing physiological, hematological and biochemical parameters, taking into account literature data on compounds similar in chemical structure. Results. The DL50 value when the substance was injected into the stomach of male rats was 1633 (1407–18 894) mg/kg, for females — 1908±360 mg/kg, for mice — 1000±363 mg/kg (a moderately dangerous substance according to GOST 12.1.007-76). It has a weak accumulation, Kkum>8. Calcium dinitrate has a pronounced irritating effect on the skin of rabbits and guinea pigs, as well as on the mucous membrane of the eye of rabbits, does not penetrate through intact skin. The data obtained in the experiment indicate a weak sensitizing activity of calcium dinitrate. The Limac of the general toxic effect of an aerosol with calcium dinitrate was set at 102 mg/m3 for changes in the functional state of the nervous system and changes in kidney function and coincides with the threshold of irritant effect (Limac) on the respiratory system of experimental animals. Conclusion. Based on the conducted studies and by analogy with the parameters of toxicometry, similar in chemical structure, 5.0 mg/m3 (aerosol, hazard class 3) is proposed as the MPCm.r. of a calcium dihydrate aerosol in the air of the working area (aerosol, hazard class 3), where special protection is required, cleaning of the skin and eyes is required. Ethics. Extract No. 3 of the Meeting of the Local Ethics Committee of Izmerov Research Institute of Occupational Health, dated March 10, 2021.