The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings have not been peer reviewed and were not evaluated in accordance with the levels of evidence criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of the NTP or the U.S. Government.
Tertiary butylhydroquinone (TBQ) is a potent antioxidant which has a wide distribution in cosmetics and in the food supply. The available toxicology data indicates that TBQ has few toxicities at the maximum tolerated dose. There are no studies conducted on the potential immunotoxicity of TBQ. Hydroquinones have been shown to be myelotoxic; thus, the immune system may represent a possible target. As a result of the wide usage of TBQ, it was selected by the NTP for immunotoxicological assessment.
The doses selected for evaluation of the immune system as a target for toxicity were 25, 75 and 150 mg/kg. Higher doses of 200 mg/kg/day for 14 days had lethal actions in the B6C3F1 mouse; thus, the high dose used in the immunotoxicity evaluation is considered to be a maximum tolerated dose for 14 days of oral exposure.
TBQ at doses between 25 and 150 mg/kg administered for 14 days by gavage produced only slight alterations in two innate immune activities. There was a slight increase in the amount of the 3rd component of complement, a slight increase in FC mediated adherence and phagocytosis by peritoneal adherent cells, and a slight increase in natural killer cell activity. These increases in innate immune response may be a physiological response to TBQ. All other immune parameters assessed were unaffected. Host resistance to one bacterial challenge (Streptococcus pneumoniae) and the B16F10 pulmonary tumor challenge were not altered by TBQ exposure. In the basic toxicology studies, liver and spleen weight increased slightly, reticulocyte number increased, total number of the polymorphonuclear leukocytes decreased, and blood glucose increased slightly in mice treated with TBQ. From previous studies on fate and distribution, there is good reason to believe that TBQ was well absorbed and distributed to the immunocompetent cells and did not cause an adverse effect. The endpoints evaluated are shown is Tables ES-1, ES-2 and ES-3.
The studies were conducted at the Medical College of Virginia Immunotoxicology Laboratory under NTP Contract No. ES 55094. The in-life phase of the studies was conducted between 5 May 1987 and 15 December 1987. The animals were housed in the animal facility of the Strauss Building.
The study director was Albert E. Munson. Kimber L. White, Jr., Michael P. Holsapple, S. G. Bradley, J. Ann McCay, Helen H. Lysy, and Deborah L. Musgrove were the major participants in the studies.
To the best of our knowledge, no significant deviations occurred that affected the quality of the data and the ability to interpret the data with respect to the immunotoxicology of tertiary butylhydroquinone.