Lactic (2-hydroxypropanoic) acid is an important metabolic component of living organisms. It is also widely used in various industries. Such a wide application of the acid in manufacturing necessitates the regulation of its content in the workplace air. Toxic effects of lactic acid are described in the literature. It was found that 2-hydroxypropanoic acid belongs to hazard level IV by the criterion of acute oral and inhalation toxicity, it causes skin irritation, severe eye damage, has no skin-resorptive or sensitizing effect, does not cause reproductive toxicity and teratogenicity. Aim of the Research. Substantiation for 2-hydroxypropanoic (lactic) acid indicative safe exposure level (ISEL) in the workplace air. Methods and Materials. Analytical, toxicological, statistical. Results. In the process of conducting toxicology study, it was found that in the conditions of inhalation experiment (intranasal modelling) 2-hydroxypropanoic acid causes changes in the state of the nervous system and affects the cellular composition of bronchoalveolar lavage of experimental animals. Therefore, after a single-dose intranasal instillation Limir = Limac, it can be classified as a substance with non-specific irritant effect. It was found that the threshold of a single-dose inhalation exposure is 20 mg/m3. Conclusions. According to the data obtained in the process of the experiment and data on toxicity parameters and health-based exposure standards of the chemical analogues, the value of ISEL for 2-hydroxypropanoic (lactic) acid in the workplace air was calculated, it is 1.0 mg/m3, aerosol. Key Words: 2-hydroxypropanoic acid, lactic acid, ISEL, workplace air.