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EC number: 249-951-5 | CAS number: 29911-28-2
In an acute inhalation toxicity study, a single group of 5 male and 5 female young adult Fischer 344 rats were exposed to an aerosol atmosphere of DPnB, at a concentration of 2040 mg/m3, by nose-only exposure for a period of 4 hours. Rats were observed for mortality and clinical signs of toxicity on the day of exposure (day 1) and 14 days thereafter. The subjects were weighed on days 1, 2, 4, 8, 11, and 15 of the study. All animals were subjected to gross necropsy. Polycarbonate tubes containing the subjects (nose cones) were attached to a 42-liter ADG nose-only inhalation chamber (30 x 60 cm) with an airflow of 30 liters/min. Aerosol was generated by metering DPnB into a stainless steel ¼ J spray nozzle using a FMI pump. DPnB was mixed with air in the spray nozzle and test material was sprayed into the chamber as an aerosol. Aerosol total mass concentrations were measured gravimetrically five times over the 4-hour exposure. Aerodynamic particle size was characterized using a 6-stage cascade impactor with increasingly diminishing pore sizes in the 6 stages. Temperature and humidity were monitored at ½ hour intervals over the 4-hour exposure.
Rats were acclimated to the nose-only polycarbonate tubes for four hours the day prior to exposure. Rats showed typical transient weight loss due to stress from being confined in the tubes.
All rats survived the first day of exposure as well as the subsequent 14-day observation period (i.e., until the scheduled sacrifice on day 15). Immediately after exposure, rats were soiled with urine and feces from being in the nose cones. Body weights for both sexes were slightly decreased (3%) on the day after exposure but gained weight steadily thereafter (not unusual with nose-only exposures). No gross pathological changes were noted in any subjects at necropsy. Characterization of the aerosol atmosphere: The time weighted average concentration of the aerosol over the 4-hour exposure period was 2.04 mg/liter or 2,040 mg/m3. Forty-eight percent of the aerosol had an aerodynamic mass median diameter of less than 3 microns, indicating that a high percentage of the aerosol was respirable within the deep lung.
The lethal concentration of DPnB is greater than 2.04 mg/liter (2,040 mg/m3). If DPnB had sufficient vapor pressure, this concentration would correspond to 262 ppm.
This study was identified as key for this toxicity endpoint because of the methods followed (which were comprehensively documented in the report). The report included GLP and Quality Assurance statements, signed by the Study Director and Head of the QA Unit, respectively. Although the study report did not specify that OECD Protocol 403: "Acute Inhalation Toxicity" was followed, the study satisfied the methods stipulated in Protocol 403. Specifically, the numbers and type of test animals used and their husbandry conditions were as prescribed in the guidance. Test material characterization was adequate. The dose level tested (in this limit test) satisfied the appropriate OECD upper limit, the length of the observation period (14 days) was sufficient, and the toxicity endpoints monitored were typical for this type assay and adequately recorded.
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