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Toxicological information

Neurotoxicity

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Description of key information

Hydrocarbons, C9-C10, aromatics, >1% Naphthalene are a combination of Hydrocarbons, C9 Aromatics and Hydrocarbons, C10-C12 Aromatics. Read across data is available for Hydrocarbons, C9 Aromatics and Hydrocarbons, C10-C12 Aromatics and the worst case scenario for each end point has been presented.

 

Hydrocarbons, C9 Aromatics:

Acute CNS effects: exposures to levels below approximately 1000 mg/m3are unlikely to produce profound acute CNS effects.

 

Sub-chronic CNS effects: NOAEC = 1500 ppm for neurotoxicity.

 

Hydrocarbons, C10-C12 Aromatics:

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

Key value for chemical safety assessment

Effect on neurotoxicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no study available

Effect on neurotoxicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Hydrocarbons, C9-C10, aromatics, >1% Naphthalene are a combination of Hydrocarbons, C9 Aromatics and Hydrocarbons, C10-C12 Aromatics. Read across data is available for Hydrocarbons, C9 Aromatics and Hydrocarbons, C10-C12 Aromatics and the worst case scenario for each end point has been presented.

Hydrocarbons, C9 Aromatics:

A was conducted to determine the neurotoxicity of high flash aromatic naphtha. Groups of 20 male rats were exposed via inhalation to 100, 500, or 1500 ppm high flash aromatic naphtha for 6 hrs per day, 5 days per week, for 13 weeks. Neurotoxicity testing was performed at 5, 9, and 13 weeks of exposure. Animals were evaluated for motor activity, fore and hind limb grip strength, audio startle response, thermal response, and hind limb foot splay. Animals were also observed weekly for clinical and behavioural signs, and pharmacotoxic signs.

 

Results of the neurotoxicity testing showed no neurotoxic effects giving an NOAEC of 1500 ppm for neurotoxicity. The 1500 ppm group showed a 12% reduction in body weight gain. Based on the reduction in weight gain, the LOAEC for the test substance is 1500 ppm for sub-chronic inhalation toxicity.

 

In an acute inhalation neurotoxicity study (McKee et al. 2010) that tested Commercial, C9 hydrocarbon solvents, statistically significant effects were apparent in the high exposure groups (5000 mg/m3). There were no statistically significant effects on visual discrimination in the intermediate exposure groups (1000 mg/m3). Post-exposure studies demonstrated the reversibility of all effects. These data, as well as evidence from previous studies, suggested that exposures to levels below approximately 1000 mg/m3are unlikely to produce profound acute CNS effects or to produce irreversible systemic toxicity.

 

In an acute inhalation neurotoxicity study (McKee et al. 2010) that tested 1,2,4-Trimethyl benzene , statistically significant effects were apparent in the high exposure groups (5000 mg/m3). There were no statistically significant effects on visual discrimination in the intermediate exposure groups (1250 mg/m3). Post-exposure studies demonstrated the reversibility of all effects.These data, as well as evidence from previous studies, suggested that exposures to levels below approximately 1000 mg/m3 are unlikely to produce profound acute CNS effects or to produce irreversible systemic toxicity.

 

Hydrocarbons, C10-C12 Aromatics:

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 (35 ppm), 600 mg/m3 (110 ppm), 2000 mg/m3 (365 ppm). 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.

 

No chronic neurotoxicity specific studies for C10-C12 Aromatic fluids were located. However, in a 13 week sub-chronic 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.

Justification for classification or non-classification

There is no data available for Hydrocarbons, C9-C10, aromatics, >1% Naphthalene. Hydrocarbons, C9-C10, aromatics, >1% Naphthalene are a combination of Hydrocarbons, C9 Aromatics and Hydrocarbons, C10-C12 Aromatics. Based on the results from read across studies, Hydrocarbons, C9-C10, aromatics, >1% Naphthalene warrant classification as STOT Single Exp. 3 (H336: May cause drowsiness or dizziness) under Regulation (EC) 1272/2008 on classification, labelling and packaging of substances and mixtures (CLP).