Acute and two-week inhalation toxicity studies in rats for Polyalphaolefin (PAO) fluid

Formal occupational exposure limits (OELs) for polyalphaolefin (PAO) fluids have not been proposed. Specific PAO fluids are utilized as aircraft hydraulics or heat sink coolants for electronics and aircraft service air. Toxicity was compared for a PAO fluid in male and female Fischer 344 rats using acute inhalation (0, 100, 500, or 1000 mg/m³ aerosol for 6 hr) and two-week inhalation (0, 20, 100, or 300 mg/m³ aerosol for 6 hr/day, 5 days/week) studies. Neurobehavioral tests following acute exposure showed that both genders were less responsive after exposure to 1000 mg/m³ PAO, and to a lesser extent following 500 mg/m³ PAO. Body weight, food, and water consumption were also affected with recovery after 24 hr. Histopathology for the acute group demonstrated an exposure response increase in severity (minimal to mild) of lesions in the posterior nasal cavities and lungs. Severity of lesions was reduced in the recovery groups (normal to minimal). Acute effects were short-lived and recoverable. Following the two-week exposure, effects were limited to lesions only in the posterior nasal cavities and lungs of the high exposure group, with less severity than in the acute exposure high concentration group. Short-term repeated exposure did not result in any cumulative effects except for minimal respiratory tract changes in the 300 mg/m³ exposure group. Data-driven operational exposure limits (OpELs) were proposed based upon Acute Exposure Guideline Levels process resulting in values of 28, 28, 14, 3.5, and 1.7 mg/m³ for 10 and 30 min, 1, 4, and 8 hr, respectively.