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Neurotoxicity

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Description of key information

Acute CNS effects: NOAEL for in rats: 600 mg/m3 (based primarily on volatility)

Key value for chemical safety assessment

Additional information

A study was conducted to evaluate the behavioral effects of rats exposed to hydrocarbons, C10, aromatics. Three test groups (with one control) comprising of 8 rats each were exposed to hydrocarbons, C10, aromatics at different concentrations including: 0 (air), 200 mg/m3 (35ppm), 600 mg/m3 (110ppm), 2000 mg/m3 (365ppm). Animals were exposed to the test atmosphere 8 hours/day for 3 consecutive days. Test methods included selected functional observational measures, automated motor activity assessment and visual discrimination performance.

 

Results of the behavioral tests indicated hydrocarbons, C10, aromatics induced disturbances in measures from different functional domains including gait abnormalities and visual discrimination performance. Some gait abnormalities were observed throughout the 3-day exposure period in rats exposed to the highest concentration of hydrocarbons, C10, aromatics (2000 mg/m3). The severity of these abnormalities was low to moderate. Effects were also observed on measures of learned performance. Exposure to the highest concentration of hydrocarbons, C10, aromatics (2000 mg/m3) induced increased latencies to make a correct choice and latencies to obtain water reinforcement, and also increased the variability in the speed of responding. The effects of exposure to hydrocarbons, C10, aromatics on performance speed were most clearly observed after the first 8-hour exposure period. Also, a small but significant decrease in the number of collected reinforcements was observed in the highest exposure group (2000 mg/m3).

 

Short-term, high-level exposure to hydrocarbons, C10, aromatics induced some mild, reversible neurobehavioral effects on functional observations and measurements of learned performance. Effects were observed during or after 3 consecutive 8 hour exposures at the highest tested concentration of 2000 mg/m3 of hydrocarbons, C10, aromatics. Exposure to 200 mg/m3 or 600 mg/m3 of hydrocarbons, C10, aromatics did not induce exposure-related neurobehavioral effects.

Justification for classification or non-classification

No chronic neurotoxicity specific studies for C10-C12 Aromatic fluids were located. However, in a 13 week subchronic inhalation study, the toxicity of C10-C12 Aromatic fluids was examined in both rats and dogs (Carpenter, 1977). There were no neurological effects noted by the researchers in either species. There were no abnormalities noted in the histopathological examination of the brain or in the peripherial nerves for either species. The NOAEC for rats and for dogs was determined to be > 0.38 mg/L, which was the highest concentration tested. Therefore, C10-C12 Aromatic hydrocarbon fluids are not likely to cause neurotoxicity.

 

C10 aromatic hydrocarbon fluids are classified as a R67: Vapors may cause drowsiness and dizziness, due to acute CNS depression.

 

Carpenter CP, Geary DL Jr, Myers RC, Nachreiner DJ, Sullivan LJ, King JM. 1977. Petroleum hydrocarbon toxicity studies XIV. Animal and human response to vapors of "high aromatic solvent". Toxicol Appl Pharmacol. 1977 Aug;41(2):235-49.