90-DAY FEEDING STUDY IN FISCHER-344 RATS OF HIGHLY REFINED PETROLEUM-DERIVED FOOD-GRADE WHITE OILS AND WAXES

Subchronic 90-day feeding studies were conducted in male and female Fi scher-344 (F-344) rats on highly refined white mineral oils and waxes representative of those used for food applications. The goal was to he lp clarify the mixed results found in other toxicity studies with labo ratory animals. Seven white oils and 5 waxes were fed at dietary doses of 20,000, 2,000, 200, and 20 ppm and compared with control groups on untreated diet; toxicity was assessed at 90 days and also after a rev ersal period of 28 days and/or 85 days. Higher molecular-sized hydroca rbons (microcrystalline waxes and the higher viscosity oils) were with out biological effects. Paraffin waxes and low- to midviscosity oils p roduced biological effects that were inversely related to molecular we ight, viscosity, and melting point; oil type and processing did not ap pear to be determinants. Biological effects were more pronounced in fe males than in males. Effects occurred mainly in the liver and mesenter ic lymph nodes and included increased organ weights, microscopic infla mmatory changes, and evidence for the presence of saturated mineral hy drocarbons in affected tissues. Inflammation of the cardiac mitral val ve was also observed at high doses in rats treated with paraffin waxes . Further studies are required to elucidate the mechanism for the resp onses observed and the relevance of these inflammatory responses in th e F-344 rat to other species, including humans.