Introduction: The complete elimination of infectious properties and alteration of the morphological composition of medical waste are achieved primarily through thermal treatment methods. However, there exists no assessment system that, given the advantages and drawbacks of each technology, allows for the selection of the optimal waste decontamination technique. Objective: To provide hygienic characteristics of healthcare waste high- and low-temperature treatment technologies and to assess their impact on ambient air and human health in the affected area in order to substantiate a set of appropriate preventive measures. Materials and Methods: Between 2017 and 2022, experimental testing of pyrolysis and low-temperature medical waste treatment plants was carried out in St. Petersburg. Using the “Ecolog” unified software for calculating ambient air pollution, we modeled emission dispersion patterns from the thermal treatment installations and determined maximum single and average daily ground-level concentrations of chemicals. Furthermore, a comprehensive assessment of chronic carcinogenic and non-carcinogenic health risks was conducted in accordance with Russian Guidelines R 2.1.10.3968–23. Results: We assessed the impact of emissions from high- and low-temperature medical waste treatment facilities on ambient air quality and human health. Pyrolysis was found to emit 28 pollutants. The maximum carcinogenic risk from the high-temperature facility was associated with benzo[a]pyrene; the highest chronic non-carcinogenic risk levels from sulfur dioxide, particulate matter, nitrogen dioxide, and benzo[a]pyrene exceeded the permissible limits. Unacceptable levels of non-carcinogenic risk were established for the pyrolysis plant: 8.07 for the respiratory system; 6.89 for additional death cases; 2.43 for developmental processes; 1.18 for the hematopoietic system, and 1.12 for the immune system. The low-temperature treatment technique was found to emit seven chemicals, predominantly of hazard class III, with maximum carcinogenic and non-carcinogenic risk values below the permissible limits. Conclusion: The pyrolysis plant poses the highest non-carcinogenic health risks, thus necessitating comprehensive preventive measures aimed to mitigate them to acceptable levels.