"Four groups each comprising 130 males and 110 females were exposed by whole-body inhalation to air (control) or to 1000, 10,000 or 20,000 ppm (0.1, 1.0 or 2.0%. v/v) CFC 142b. The exposure duration was 6 hr/day on 5 days/wk. Exposure was continued for 104 wk for the combined chronic toxicity and oncogenicity study (initially 110 males and 110 females/group).Ten males/group were exposed for only 13 wk in a bone-marrow cytogenicity assay and ten males/group were exposed for 15 wk in a dominant lethal assay. Test material passed through 0.5-in. diameter copper lubing immersed in an ethylene glycol chilled bath and through a liquid volume flowmeter prior to division into three delivery lines, volatilization at 38oC, and measurement of gas flow-rate. The CFC 142b gas for each 10 m³Rochester-design chamber was diluted with filtered, temperature- and humidity controlled, non-recirculated air to achieve the designated chamber concentrations. Chamber air flow was maintained in the range 2.06-3.4 m³/min providing 12.4-20.4 air changes/hr. Chamber concentrations were monitored six times/day using on-line gas liquid chromatography (Tracor model SSO equipped with a flame-ionization detector, 5% OV-101 on 80-100 mesh Supelcoport column, 50°C column temperature, and 200^oC detector temperature."

"Exposures for the dominant lethal test were continued for 15 wk followed by eight weekly matings of each male with two untreated virgin females."

"There was close agreement between planned in halation chamber concentrations (0.1, 1 and 2%) and measured concentrations throughout the 2-yr study. The mean 2-yr analytical concentrations (± 1 SD) of CFC 142b were 0.099 ± 0.02, 1.01 ± 0.11 and 1.95 ± 0.20% (v/v) respectively."

Note: Concentrations in mg/m³ were determined by the extractor using an online conversion calculator and average molecular weight of 100.49 g/mol.

Male Sprague-Dawley-derived CD Rats