Hydrocarbons, C7-8

Endpoint summary

Description of key information

Oral LD50 (rat) > 5840 mg/kg bw
Dermal LD 50 (rat) > 2920 mg/kg bw
Inhalative LC50 (rat) > 23300 mg/m³

Additional information

Oral

 

There are no data available on the acute oral toxicity of hydrocarbons, C7-C8, cyclics. However, there are reliable data available for another category member. Thus, read-across was conducted based on a category-approach.

The acute oral toxicity of hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics was tested following a standard method. Two male and two female rats were exposed to 1, 2, 4, or 8 mL/kg of undiluted test substance orally by gavage. The animals were then observed for the next 9 days for mortality. No animals of either sex died during the study. The LD₅₀was > 8 mL/kg for both male and female rats. Based on the density given in the study report, the LD₅₀was calculated to be higher than approx. 5840 mg/kg bw (Shell Chemicals, 1977). This finding is corroborated by results from a supporting study conducted with methylcyclohexane (Treon et al 1943), where the LD50 for rabbits was found to be in the range of 4000 -5000 mg/kg bw.

 

Inhalation

 

There are no data available on the acute toxicity of hydrocarbons, C7-C8, cyclics, after inhalative exposure. However, there are reliable data available for other category members. Thus, read-across was conducted based on a category-approach.

Wistar rats (5/sex) were exposed via inhalation (whole body) to hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics at 23300 mg/m³ for 4 h (similar to OECD 403). Clinical signs during exposure included signs of slight irritation, partial closing of the eyes, lacrimation, a reduced respiration rate and restless behavior. One male rat died during the exposure. The signs recorded during the observation period were hyperactivity and abnormal breathing. Reduced body weight for 1-2 days and reduced food consumption for 1 day following exposure. The lung weight for the decedent rat was high, but within normal limits for the others. The LC₅₀was greater than 23300 mg/m³ (Shell Chemicals, 1988).

In another study, male and female Charles River CD rats (2/sex/concentration) were exposed via whole body inhalation to hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics at 11000, 29000, 33000, 42000, or 49000 mg/m³ for four hours (similar to OECD 403). Clinical signs included mild piloerection, restlessness and tremors of the fore-paws. None of 4 rats died at 33000 mg/m³, 3 of 4 rats died at 42000 mg/m³ and 7/8 rats died at 49000 mg/m³. Before death the rats lapsed into a comatose state, and one animal showed excess salivation and had a blood-stained nasal discharge. Surviving animals exhibited mild excitability on removal from the chamber and slight ataxia was observed, however, this effect disappeared within 1 h after the end exposure. The animals surviving the exposure also survived the subsequent 14 day observation period. The LC₅₀was 33000 - 42000 mg/m³ (Shell Chemicals, 1977).

Male Wistar rats (10/concentration) were exposed in a further study via whole body inhalation to Ligroine (VM&P Naphatha) at 4400, 9800 or 26000 mg/m³ for four hours (similar to OECD 403). Mortality was 100% at 26000 mg/m³; no deaths occurred at 9800 or 4400 mg/m³. Clinical signs in rats at higher concentrations included eye irritation and central nervous system depression (poor coordination with convulsions preceding death). Rats exposed to 4.4 mg/L did not exhibit physical signs during or after exposure or during 14 days of observation. Gross necropsy observations of rats that died after 26000 mg/m³ Ligroine (VM& P Naphtha) were congestion of lung and liver. Bile duct proliferation and increased number of leukocytes in sinusoids of the spleen were noted in 3 of 6 livers examined histologically. Rats killed 14 days after inhaling 9800 or 4400 mg/m³ for 4 hrs evidenced singly occurring bronchitic effects and extraneous lesions in organs other than the lung. The LC₅₀was 16000 mg/m³ (Carpenteret al., 1975).

In a study by Treon et al. (1943) rabbits were exposed to methylcyclohexane at concentrations of 0.948 to 59.9 mg/L. The LC50 was found to be 39.55 to 59.9 mg/L. 4/4 animals died 1h 10 min after onset of exposure at 59.9 mg/L; 4/4 rabbits died after 2 weeks of repeated exposure (6 h/day, 5 days per week) at 39.55 mg/L.

 

Dermal

 

There are no data available on the acute dermal toxicity of hydrocarbons, C7-C8, cyclics. However, there are reliable data available for another category member. Thus, read-across was conducted based on a category-approach.

Hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics were applied on the shaved backs of Charles River CD rats (2/sex/dose) at 1, 2, and 4 mL/kg bw (730, 1460, and 2920 mg/kg bw) for 24 hours in accordance with the method of Noakes and Sanderson, 1969 [Br. J Indust. Med 26:59-64] (similar to OECD 402). No deaths or clinical signs were observed. The LD₅₀was greater than 4 mL/kg bw, corresponding to 2920 mg/kg bw (Shell Chemicals, 1977).

Justification for classification or non-classification

Based on read-across within a category approach, the available data on the acute toxicity of hydrocarbons, C7 -C8, cyclics are conclusive but not sufficient for classification. However, acute exposure may result in non-lethal narcotic effects and hydrocarbons poses aspiration hazard.

DSD: R65-67

 

CLP: Aspiration Toxicity Category 1, STOT Single Exposure Category 3 (narcosis)