Experimental risk assessment of chronic oral exposure to unsymmetrical dimethylhydrazine

Introduction. The problem of long-term pollution of primary environment objects and, accordingly, the safety of population lives in connection with unsymmetrical dimethylhydrazine as a component rocket fuel seems to be quite urgent. In this case, the danger lies in the prolonged exposure to the compound in small quantities.

Materials and methods. As the object of these studies, we used unsymmetrical dimethylhydrazine (“heptyl”, 1,1-dimethylhydrazine (CH₃)₂N₂H₂, CAS No. 57-14-7) with the substance mass fraction equal to 99.0% and the specific gravity d₄²⁰ = 0.7914 g/cm³. “Heptyl” is highly soluble in water. Toxicological studies on laboratory animals were carried out following the requirements of the current guidelines.

Results. In the course of the experimental studies, chronic 6-month oral intake of unsymmetrical dimethylhydrazine in rats at doses of 4.0 · 10^–4 mg/kg, 8.0 · 10^–5 mg/kg and 1.5 · 10^–5 mg/kg was accompanied by changes in the complex of physiological, behavioural, haematological, biochemical and immunological parameters. The linear dose-effect dependence was registered both in the width and depth of the effect. At the same time, the maximum number of statistically significant changes was revealed when exposed to the compound at the highest level and amounted to 26, of which 7 had bisigmal deviations from similar indices in the control group. In the second experimental group, a specific decrease in the toxic effect was recorded, as evidenced by 14 significant shifts in indicators, 3 of which went beyond two sigmas relative to control. In the third experimental group of animals, the considered ratio was 4/0.

Conclusions. Based on the current diagnostic criteria, the dose of unsymmetrical dimethylhydrazine 1.5 · 10^–5 mg/kg was adopted as the threshold for chronic general toxic action. The revealed features of the negative impact of unsymmetrical dimethylhydrazine were taken into account when substantiating its MPC in water bodies.

Contribution:

Maslennikov A.A. — research concept and design, writing text;

Antonov V.A. — research concept and design;

Khodykina N.V., Velikorodnaya Yu.I. — data collection and processing;

Grishina M.A. — statistical data processing;

Filatov B.N. — editing.

All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version.

Conflict of interest. The authors declare no conflict of interest.

Acknowledgement. The study was carried out within the framework of the State Contract for 2019–2020 “Experimental substantiation of the maximum permissible concentration of unsymmetrical dimethylhydrazine in the water of water bodies for domestic, drinking and cultural water use”.

Received: June 26, 2021 / Accepted: November 25, 2021 / Published: March 10, 2022