Mated rats were ranked by their body weights on gestation Day (GD) 1 and assigned to control or three experimental groups by random sampling from strata established within the ranked list such that each of the four groups contained 24 females. Each group consisted of 20 females. Groups of rats or rabbits were designated as either a control (0 ppm), 5000, 15,000, or 50,000 ppm HCFC-124.

"The rats designated for the developmental study were exposed together with the rats assigned to the subchronic study. Four 1.4 m^3 stainless steel and glass exposure chambers were used for the exposures. The chambers were operated in a one-pass, flow-through mode with the air flow rates targeted at 300 liters/min. During exposure, the airflow rates, temperature, and relative humidity of the chamber air were recorded at approximately 5-min intervals. Chamber oxygen content was determined at least twice daily. During exposure, rats were housed two per cage."

Exposures for rats dedicated to the developmental study were conducted 6 hr per day during GD 7-16.

"The test material was introduced into the chamber air supply as a vapor. It was mixed with incoming conditioned air by turbulence. Chamber concentrations of HCFC-124 were controlled by varying the vapor flow rates into the exposure chamber. Conditioned air alone was metered in an identical manner into the respective control chambers. To maintain the cylinders containing the test material at a constant temperature, they were warmed to offset the temperature decrease due to volatilization of the liquid material. Chamber atmospheres were analyzed by gas chromatography at approximately 30-min intervals during each 6-hr exposure period. Samples were drawn by vacuum pump from representative areas of the chambers where the animals were exposed. Although different model gas chromatographs and columns were used in these four studies, the analytical procedures were similar and have been summarized as follows: Gas samples were analyzed with a gas chromatograph equipped with a flame ionization detector. Nitrogen was utilized as the carrier gas. Samples were chromatographed isothermally on stainless steel columns packed with either 2% OV-101 on 100/120 mesh Chromosorb WHP or Porapak Q 100/120 mesh. The atmospheric concentration of HCFC-124 was determined by comparing the detector response of chamber samples to that of gas standards through the use of standard curves. The gas standards were prepared by injecting known volumes of HCFC-124 vapor into gas bags which contained known volumes of air."

The overall mean concentrations of HCFC-124 in the exposure chambers were within 98-101% of the target concentrations of 0, 5000, 15,000, and 50,000 ppm (Table 1). In addition, the standard deviations for the overall mean daily chamber concentrations ranged between 2 and 6% of the target concentrations. Mean daily chamber temperatures ranged between 20 and 27°C, and mean daily chamber humidity ranged between 35 and 78%. The chamber environmental conditions were judged to be satisfactory to maintain the health status of the animals.

P0 Female Crl:CD BR Rats