TOXICITY EVALUATION OF PETROLEUM BLENDING STREAMS - INHALATION SUBCHRONIC TOXICITY NEUROTOXICITY STUDY OF A LIGHT ALKYLATE NAPHTHA DISTILLATE IN RATS/

A 13-wk inhalation study was conducted with Sprague-Dawley CD rats (12 /sex/group) were exposed by inhalation for 13 weeks to a light alkylat e naphtha distillate (LAND-2, C-4-C-10; average molecular weight 89.2) at actual average concentrations of 0 (room air), 668, 2220, or 6646 ppm, 6 h/d, 5 d/wk; 12 additional rats/sex in the control and high dos e groups were held after final exposure for a 4-wk recovery period. Th e highest exposure concentration was 75% of the lower explosive limit Standard parameters of subchronic toxicity were measured throughout th e study; at necropsy, organs were weighed and tissues processed for mi croscopic evaluation. Neurotoxicity evaluations consisted of motor act ivity (MA) and a functional operational battery (FOB) measured pretest , during 5, 9, and 14 wk of the study, and after the 4-wk recovery per iod. Whole-body perfusion and microscopic examination of selected orga ns and nervous tissue from the control and high dose rats were conduct ed at the end of exposure. No test-related mortality or effects on phy sical signs, body weight, or food consumption were observed. Statistic ally significant increases in absolute and relative kidney weights in high-exposure males correlated with microscopically observed hyaline d roplet formation and renal nephropathy, effects in male rats that are not toxicologically significant for humans. Increased liver weights in both sexes at the highest dose had no microscopic correlate and appea red reversible after the 4-wk recovery period. Exposure to LAND-2 at a ny dose did not produce neurotoxicity measured by MA, FOE, or neuropat hology. The no-observed-effects level (NOEL) for LAND-2 was 2220 ppm f or subchronic toxicity and greater than or equal to 6646 ppm for neuro toxicity.