[The validation of the maximum permissible concentration of pyromellitic dianhydride in the atmosphere].

The maximum allowable concentration (MAC) of pyromellitic acid dianhydride (PMAD) in the ambient air was substabtiated by physiological, hematological, and physiological methods. The inhalation of this substance by animals reduced their body weight, erythrocytic osmotic resistance, enhanced animals' sensitization. The mean daily MAC of PMAD was found to be 0.01 mg/m3. PMAD was considered to be Hazard Class 2.