Acute Inhalation Toxicity and Blood Absorption of 3-Nitro-1,2,4-Triazol-5-One (NTO) in Rats

Abstract : This toxicology study was conducted to determine the 4-hour inhalation median lethal concentration (LC50) of 3-Nitro-1,2,4-Triazol-5-One (NTO) in male and female rats. Nose-only exposure to the highest-achievable aerosol atmosphere of NTO (0.18 mg/L) did not induce any compound-related mortality, adverse toxic signs, body weight changes, or gross necropsy findings. A secondary objective was to determine the effect that two different routes of administration (inhalation and oral) had on the absorption of the chemical into the bloodstream. Blood samples were collected and analyzed from exposed rats at 7 time points for those exposed via inhalation and 6 different time points for those given a calculated equivalent oral dose. The results of the blood absorption study indicated that, under the stated study conditions and limitations, acute exposure to NTO via inhalation appears to induce higher whole blood concentrations in laboratory rats compared to those exposed via oral gavage.