One- and Three-Month Inhalation Studies with Coolanol 25R

Abstract

Male and female Sprague-Dawley rats were exposed to an aerosol of COOLANOL 25R dielectric heat transfer fluid (COOLANOL 25R) for 6 hid, 5 d/wk at target-exposure levels of 0, 15, 60, or 120 mg/m³ in a 1-mo study and 0, 1, 5, or 30 mg/m³ in a 3-mo study. In the 1-mo study, high-exposure males and mid- and high-exposure females manifested red perinasal encrustation and discharge during postexposure periods, beginning with wk 2 of the study, but there were no clinical signs of pulmonary impairment, such as altered animal breathing patterns, either during or after COOLANOL 25R exposures. COOLANOL 25R-exposed rats in all exposure groups demonstrated hypertrophy and hyperplasia (predominantly goblet cell) in the most rostra1 respiratory epithelium of the nasal turbinates following histologic examination. With the exception of low-exposure male rats, animals from all other COOLANOL 25R treatment groups demonstrated both macroscopic and microscopic lung lesions. In the 3-mo study, there were no clinical signs of chemically induced toxicity and no treatment-related gross or histological changes in the respiratory systems of the rats exposed to COOLANOL 25R aerosols. The results obtained from these studies suggest that COOLANOL 25R aerosols, only at levels in excess of those that one would expect to find in a workplace environment, may produce nonspecific and reversible lung lesions in rats.