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

ABSTRACT

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.

KEYWORDS:

• Polyalphaolefin
• toxicity
• inhalation
• neurobehavior
• histopathology

Acknowledgments

Use of a commercial name and product does not constitute endorsement of the product by the U.S. Air Force, U.S. Navy, or U.S. Army. Support for this research was provided through the former Aerospace Toxicology Program by the Air Force Research Laboratory, 711th Human Performance Wing, Airman Systems Directorate at Wright-Patterson Air Force Base (AFB), OH. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the U.S. Air Force, the Department of the Navy, Department of Defense, nor the U.S. Government. This work was prepared as part of official duties by employees of the U.S. Government. Title 17, U.S.C.§105 provides that copyright protection under this title is not available for any work of the U.S. Government.