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Diss Factsheets

Administrative data

Description of key information

Key acute oral (OECD 401) and dermal (OECD 402) studies were identified for unrefined acid treated oils.  A read-across acute toxicity for inhalation (OECD 403) was identified from distillate aromatic extracts.  LD50 and LC50 values were as follows:
• The oral LD50 was > 5000 mg/kg bw in male and female rats exposed to unrefined/acid treated oils.
• The dermal LD50 was > 2000 mg/kg bw in male and female rabbits exposed to unrefined/acid treated oils.
• The LC50 was >5 mg/L (equivalent to 5000 mg/m3) in male and female rats exposed to distillate aromatic extracts.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Dose descriptor:
5 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion
Dose descriptor:
5 000 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion
Dose descriptor:
2 000 mg/kg bw

Additional information

Unrefined/acid treated oils are of low acute toxicity, with an oral LD50greater than 5000 mg/kg (rat), an inhalation LC50greater than 5 mg/L (rat), and a dermal LD50greater than 2000 mg/kg (rabbit). Subsequent to high oral doses of 5000 mg/kg, the only clinical signs observed included hypoactivity and diarrhoea during the first 3 days with all animals returning to normal state by day 14. Additionally, no visible lesions were observed at gross necropsy. Following a dermal application of 2000 mg/kg for 24 hours, there were no mortalities or signs of clinical toxicity observed in rabbits. In a read-across inhalation toxicity study, rats exposed for 4 hours to increasing aerosol concentrations (1, 1.5, 2.5, 3.5, and 5.0 mg/L) of a hydrotreated lubricant base oil exhibited acute morphological changes to the lung tissue that appeared dose-related. This was true for animals that died subsequent to exposure while few exhibited acute morphological abnormalities were observed in the lungs of 14 -day survivors.

Acute Oral Toxicity

In a key acute oral toxicity study (Klimisch = 1), 5 male and 5 female Sprague-Dawley rats were orally exposed to a single dose (5000 mg/kg) of unrefined light paraffinic distillate (API, 1986a). Animals were observed for clinical signs and mortality at hourly intervals for the first 6 hours post-dosing and twice daily thereafter and body weights were recorded prior to fasting, prior to dosing and at 7 and 14 days post-dosing. At 14 days, all surviving animals were killed and subjected to a gross examination. There were no deaths during the study and growth rates were unaffected by dosing. Clinical signs that occurred during the first 3 days included hypoactivity and diarrhoea. All animals returned to normal by day 14. At gross necropsy, there were no visible lesions. The oral LD50 in this study was >5000 mg/kg bw.  

Acute Inhalation Toxicity

For acute inhalation toxicity, data was not available for unrefined/acid treated oil and therefore, data is being read across from distillate aromatic extracts. This substance represents the worst case scenario. In this study, groups of young adult Sprague Dawley rats (5/sex) were exposed by inhalation route to distillate aromatic extract for 4 hours to whole body at concentrations of 5.0 mg/L (ARCO, 1983; Klimisch score=1). Animals then were observed for 14 days.


All animals were lethargic during the last 2 hours of exposure. From hour 2 of treatment until the first hour post-exposure, animals kept their eyes partially closed and were lacrimating. One rat displayed red nasal discharge following exposure and red ocular discharge. Another rat exhibited yellow eye discharge during the fourth hour post-exposure and red eye discharge the morning following discharge until the end of the third day post-treatment. These findings are considered related to treatment. Three rats of each sex showed pallor and/or swelling of the kidneys. These findings may be related to treatment. The acute aerosol LD50 of distillate aromatic extract is greater than 5.0 mg/L of air (equivalent to 5000 mg/m3). 

In a supporting read-across study from the lubricant base oils, 5 male and 5 female young adult rats were exposed by the inhalation route to hydrotreated light naphthenic distillate for 4 hours at concentrations of 0, 1.0, 1.5, 2.5, 3.5, or 5.0 mg/L (API, 1987). Animals then were observed for 14days. Substances classified as unrefined/acid treated oils have physico-chemical properties that are similar to those of lubricant base oils (LBOs). Both LBOs and unrefined/acid treated oils are produced by distilling crude oil but with differing severity of refining. This study, however, was only considered supporting because the study was on a poorly refined mineral oil that had high levels of PACs and was also carcinogenic.


Overall, body weight results were considered unremarkable. Histopathological examination of the lung tissues yielded dose-related acute morphological changes consistent with acute toxicity for animals dying during the study. Few morphological abnormalities were observed in the lungs of 14 -day survivors. Based on the resultant mortality, the LC50 was 2.18 mg/L with 95% confidence limits of 1.64 to 2.71 mg/L for both male and female rats, 2.18 mg/L with 95% confidence limits of 1.80 to 2.55 mg/L for the combined sexes.

Acute Dermal Toxicity

In a key acute dermal toxicity study (Klimisch = 1) undiluted test material (unrefined light paraffinic distillate) was applied as a single dose (2000 mg/kg) to the shorn, abraded skin of 4 male and 4 female rabbits and covered with an occlusive dressing for 24 hours (API, 1986a). The rabbits were observed for clinical signs and mortality every hour for the first 6 hours, then daily for dermal irritation and twice daily for clinical signs and mortality. Observations were carried out for a 14-day post-treatment period. Body weights were recorded prior to administration of the test material, again 7 days post-dosing and at study termination (14 days). At termination, all surviving animals were killed and subjected to a gross examination. No mortalities and no clinical signs of toxicity except for dermal irritation at the site of application were observed during the study period. The dermal LD50for this study was >2000 mg/kg-body weight.

Justification for classification or non-classification

Based on evaluation of all the acute toxicity data discussed above, unrefined/acid treated oils do not meet the criteria for classification as an acute oral, inhalation or dermal toxicant under the EU CLP Regulation (EC No. 1272/2008) because the LD50/LC50 values are greater than the limits for classification defined in the criteria.


Regulatory classification and labelling for aspiration toxicity relies on the measured or calculated kinematic viscosity of a substance at 40°C rather than results from toxicological studies with animals. Hydrocarbons with kinematic viscosities less than or equal to 20.5 mm2/sec

at 40°C are classified for aspiration toxicity

according to EU CLP Regulation (EC No. 1272/2008) criteria. Members of this category which meet this criteria are classified as Aspiration Category 1 (H304)according to the EU CLP Regulation (EC No. 1272/2008).