Alkanes, C8-9-iso-

Endpoint summary

Description of key information

Oral LD50 (rat) > 10 mL/kg bw
Dermal LD 50 (rabbit) > 3.16 mL/kg bw
Inhalative LC50 (rat) = 17300 - 23300 mg/m³

Additional information

Oral

 

The acute oral LD₅₀value in rats was greater than 10 mL/kg for hydrocarbons, C7-C9, isoalkanes, belonging to the same category as the test substance, in two studies performed according to a protocol similar to OECD 401. The test material produced no deaths at any dosage level tested (31.6-10000 µL/kg body weight). There were no pathological findings in any animal at autopsy following sacrifice. The animals at all dosage levels seemed normal in appearance and behaviour throughout the study period (ExxonMobil Chemical, 1961).

 

Inhalation

 

Hydrocarbons, C7-C9, isoalkanes, have been tested in several studies for acute inhalation toxicity following both standard (similar to OECD 403) and non-standard protocols.

In one study, 6 rats (male and female) were exposed to a nominal concentration of 21500 mg/m³ (21000 mg/m³ actual concentration) in a whole body chamber for 4 h. Another group of 6 animals was sham-exposed to room air and served as control. No mortalities occurred throughout the duration of the study (14 days). After exposure 3 of 12 rats had dried red nasal discharge, 1 of 12 rats had slight salivation, and 1 of 12 rats had slight lacrimation. All abnormal signs in the dosed animals were cleared by day 2 post-exposure. One control rat exhibited dried red nasal discharge on days 10 and 11 post-exposure, but this sign was considered inconsequential to the study outcome. There were 7 control rats and 8 dosed rats without abnormalities at necropsy. Of the remainder, there was a greater incidence of focal lung discoloration in the controls than in the dosed rats, a comparable incidence of dilated renal pelvis, and one instance of a dosed rat having a broken upper incisor. None of theses observations was considered to be related to treatment with the test substance. The LC₅₀was greater than 21000 mg/m³, corresponding to 4504 ppm (ExxonMobil Chemical, 1985).

In two earlier studies, rats (6 males) were exposed for 4 h to 1850, 3100, 5750 and 10000 ppm and 1050, 2390, 4450 and 7140 ppm, respectively. In the first study, mortalities occurred at 5750 ppm (6/6) and higher. Exposure to lethal concentrations induced a rapid and dramatic response. Repeated episodes of violent epileptiform convulsions, interspersed with periods of running and jumping. Death occured within 17 minutes for all rats tested at the highest concentration. The lungs of animals which died during exposure showed hemorrhagic areas with gray spots on the surfaces. Severe lung congestion was an isolated finding and lung consolidation was seen infrequently. In general, the livers and kidneys were congested in these animals, but all other organs appeared normal. Animals surviving the 14-day observation period revealed little of interest at autopsy. In a few instances, hemorrhagic areas were noted on the lung surfaces and an occasionally darkened liver or kidney was seen. All other organs appeared normal. The LC₅₀value was calculated to be 4240 ppm, corresponding to 17300 -22200 mg/m³. The range of LC₅₀is due to unknown amounts of hydrocarbons in the test substance with chain lengths ranging from C7 to C9 (ExxonMobil Chemical, 1962).

In the second study, 3/6 and 6/6 animals died at 4450 and 7140 ppm, respectively. Animals exposed to lethal concentrations exhibited clonic convulsions, laboured respiration, ataxia, and prostration preterminally. At the highest concentration, all six rats died within 1 hour; animals which survived 4 hours of exposure to 4450 ppm had a bloody exudate around the eyes and nose at the end of the exposure period. The lungs of animals which died during exposure showed hemorrhagic areas with gray spots on the surfaces. Severe lung congestion was an isolated finding and lung consolidation was seen infrequently. In general, the livers and kidneys were congested in these animals, but all other organs appeared normal. Animals surviving the 14-day observation period revealed little of interest at autopsy. In a few instances, hemorrhagic areas were noted on the lung surfaces and an occasionally darkened liver or kidney was seen. All other organs appeared normal. The LC₅₀value was 4450 ppm, corresponding to 18200 -23300 mg/m³. As mentioned above, the range of LC₅₀is due to unknown amounts of hydrocarbons in the test substance with chain lengths ranging from C7 to C9 (ExxonMobil Chemical, 1962).

Two further studies were performed on guinea pigs and rats following non-guideline procedures. In each study, 5 animals were exposed to 9400 mg/m³ for 10 min every 30 min during 4 h, yielding a total of eight 10-min exposures. In both studies, none of the guinea pigs or rats exposed died during the exposures or during the 14-day observation period which followed. No pathological, histopathological or behavioural effects were observed throughout the study. The LC₅₀value in both guinea pigs and rats was greater than 9400 mg/m³ (ExxonMobil Chemical, 1972).

 

Dermal

 

Two studies were performed in which hydrocarbons, C7-C9, isoalkanes, were applied to the clipped, intact abdominal skin of albino rabbits (4/sex/dose) at 100, 316, 1000, 3160 µL/kg bw for 24 h under occlusive conditions. In the first study, there were three deaths, one each at the 100, 1000, and 3160 µL/kg bw levels. These deaths were apparently the result of a severe intestinal infection. In the 100 µL/kg group one animal showed diarrhea on day 11 and on day 14 depression, labored respiration and diarrhea. In the same group, congestion of the kidneys, inflammation of the samll intestine, and a large amount of fluid in the gastrointestinal tract was found in one animal at necropsy. At the 3160 µL/kg level, firm, elevated, blanched areas on the gallbladder, and extensive amount of fluid in the peritoneal cavity, and inflammation of the intestines were observed.

In the second study, no deaths at any dosage level occurred. Appart from 3 rabbits all other animals showed normal behaviour and appearance throughout the study. Two rabbits from the lowest dose treatment showed diarrhea for two to four days and a decrease in body weight. At autopsy one showed paleness of the cortical portion of the kidneys, the other an excessive amount of clear fluid in the peritoneal cavity and congested, pitted, tough kidneys. One rabbit of the high dose group showed inflammation of the intestines.

In both studies the following dermal effects were noted: After removal of the binders at the end of the exposure period, the abdomens and binders were dry. At this time, the exposed skin areas of the animals showed a slight degree of erythema. Within an additional one to three days, the erythema had completely subsided in all animals. The low dose animals showed no other signs of irritation during the remainder of the observation period. The high dose animals showed slight or moderate desquamation during the final few days of the first week and during the second week. At termination, however, the exposed skin of the surviving animals was completely free of signs of irritation.

The LD₅₀value was greater than 3.16 mL/kg bw in both studies (ExxonMobil Chemical, 1961).

Justification for classification or non-classification

The available data on the acute toxicity of hydrocarbons, C8-C9, isoalkanes 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)