Note: Concentration levels were converted from ppm to mg/m³ by the extractor using an online conversion calculator and entering the target concentrations and average molecular weight of 216.03 g/mol.

Administration / exposure

Route of administration: inhalation: gas

Type of inhalation exposure: whole body

Vehicle: air

No. of animals per sex per dose: 10 rats each for the control and high-concentration groups, and five rats each for the low- and intermediate-concentration

Control animals: yes

Duration of treatment / exposure: Six hours per day

Frequency of treatment: Five days per week for a total of 20 exposures over a four-week period (weekends excluded)

Details on study design:

Dose selection rationale: A range finding experiment was conducted in male and female rats exposed whole-body for six hours/day for four consecutive days to 18000 ppm of test substance. During these exposures, rats exhibited a diminished response to an alerting stimulus and a diminished activity level when compared to baseline evaluations prior to each exposure. Clinical signs of toxicity were limited to irregular respiration in one male and one female rat immediately after the second and third exposures, respectively. Rats had slight body-weight losses during the exposure period. For the four-week study, the highest concentration level of the test substance was targeted at 18000 ppm. This concentration was selected after considering the findings of the aforementioned information and the safety issues associated with generating the test substance gas in the 150 L exposure chambers. The high level exposure concentration at 18000 ppm is 60% of the lower explosive limit (30000 ppm) of the test substance.

Details on inhalation exposure:

TEST ATMOSPHERE -

Brief description of analytical method used: The atmospheric concentration of the test substance was determined by gas chromatography at approximately 20-minute intervals during each six-hour exposure. Gas samples were drawn by vacuum pump from representative areas of the chamber where rats were exposed. Chamber atmosphere samples were directly injected into a gas chromatograph equipped with a flame ionization detector for analysis of the test substance concentration. All samples were chromatographed isothermally at 85°C on a 3% OV-17 Chromosorb column. The atmospheric concentration of the test substance was determined from a standard curve derived from gas standards. The gas standards were prepared prior to each exposure by injecting known volumes of test substance gas into Tedlar® bags that contained known volumes of air."

Details on analytical verification of doses or concentrations:

The analytically determined mean concentrations ± SEM of the test substance in the exposure chambers targeted to 500, 3000, or 18000 ppm were 500 ± 2.1, 3000 ± 10, and 18000 ± 57 for the 20 exposures. Daily mean concentrations were consistent from day- to-day throughout the study. The mean daily concentrations were within ±7% of the targeted exposure concentrations. During the 10th exposure, brief excursions in atmospheric concentration occurred in all test chambers during the first hour of exposure. The chamber concentrations measured during this period ranged from 31 to 920 ppm in the 500 ppm chamber, 260 to 2800 ppm in the 3000 ppm chamber, and 5500 to 17000 ppm in the 18000 ppm chamber. The excursions were due to the test substance condensing in the stainless steel lines. The problem with the generation system was corrected and the exposures continued without additional excursions. The brief excursions in chamber concentration were considered not to have adversely affected the results of the study. The analytically determined concentrations were considered acceptable for evaluating the toxicity of the test substance at the selected targeted concentrations.

VEHICLE - Composition of vehicle: Houseline air"

Female Crl:CD(SD)BR Rats