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Description of key information

Available non-human data for CAS 68516-20-1, a low benzene naphtha stream and supporting data from one related stream (CAS 64741-68-0) and data on the specific component toluene, indicate that acute toxicity is expected to be low. Low benzene naphtha streams do not pose an acute hazard following ingestion (oral LD50 > 2000 mg/kg bw) or skin contact (dermal LD50 > 2000 mg/kg).  The acute inhalation 4 hour LC50 is greater than saturated vapour pressure for the two streams considered and > 20 mg/L for toluene.  
However following acute inhalation exposures to toluene in humans a number of subjective sensations such as headache, dizziness, feeling of intoxication, irritation and sleepiness and decreases in acute neurobehavioural performance are seen. The NOAEC for acute neurobehavioural effects in humans is 50 ppm (188 mg/m3) and labelling (R67) will be required as low benzene naphtha streams contain up to 50% toluene.

Key value for chemical safety assessment

Additional information

There are acute toxicity data on CAS 68516 -20 -1, a low benzene naphtha stream and supporting data from one related stream API 83-04 (CAS 64741-68 -0) which is a petroleum based naphtha comprising up to 100% aromatics, including substituted mono and di-aromatics. There are also data for the major component toluene. Benzene and 1, 3 butadiene are present at <0.1%.

Non-human information

Acute toxicity: oral

The acute oral toxicity of low benzene naphtha streams is low. An LD50 value greater than 2000 mg/kg bw was obtained for CAS 68516-20-1. In a study with the related stream CAS 64741-68-0 the acute oral LD50 was 4820 mg/kg bw to male rats and 5800 mg/kg bw to female rats. There were no significant clinical signs or pathology findings in these studies. 

Acute toxicity: dermal

The dermal acute toxicity has been tested for the low benzene naphtha streams CAS 68516-20-1 and one related stream CAS 64741-68-0 and the LD50 values are greater than 2000 mg/kg bw. In both studies the test substance was in contact with the skin for approximately 24 hours and an occlusive dressing was used. 

 

Acute toxicity inhalation

The 4 hour LC50 values of the low benzene naphtha stream CAS 68516-20-1 and one related stream CAS 64741-68-0 are greater than the saturated vapour pressure (5.81 and 5.04 mg/L air). The LC50 of toluene was calculated to be > 20 mg/L EU RAR (2003), but there was unsteady gait and other indications of neurobehavioural activity at concentrations < 20 mg/L.

 

Human information

 

There are no specific studies on the oral, inhalation or dermal toxicity in humans for streams in this category.

Data from human exposures provides information on acute toxicity for toluene:

Toluene (Classification: EU – R65, R67; GHS/CLP: Category 1, H304, Cat 3 H336): The acute effects of toluene inhalation exposure include headache, dizziness, feeling of intoxication, irritation and sleepiness and decreases in acute neurobehavioural performance at concentrations ≥ 75 ppm (EU RAR, 2003). A NOAEC of 50 ppm (188 mg/m3) can be determined for acute neurobehavioural effects in humans (Muttray et al, 2005).

References

EU RAR (2003a). European Union Risk Assessment Report for Toluene. EC Joint Research Centre http: //ecb. jrc. ec. europa. eu/DOCUMENTS/Existing- Chemicals/RISK_ASSESSMENT/REPORT/toluenereport032. pdf

Muttray A, Spelmeyer U, Hommel G, Oesch F, Jung D, Rose D, Mayer-Popken O, Rossbach B and Letzel S (2005). Acute exposure to 50 ppm toluene does not increase sleepiness. Environ. Toxicol. Pharmacol. 19, 665-669.

Aspiration is a known hazard of hydrocarbons and is based on the physical characteristics of the low benzene naphtha streams. Kinematic viscosity values obtained range from 0.38 to 0.83 mm2/s at 40oC. Classification is warranted as these values are below the relevant cut off values for DSD of 7mm2/s and for GHS/CLP of 20.5 mm2/s (hydrocarbons).

Justification for classification or non-classification

There are sufficient data on component substances to indicate that low benzene naphtha streams are of low acute toxicity by the oral, dermal and inhalation routes and do not warrant classification for these end-points under Dir 67/548/EEC or GHS/CLP.

The low kinematic viscosity of low benzene naphtha streams warrants labelling as follows: harmful Xn, R65, "May cause lung damage if swallowed" under Dir 67/548/EEC and under GHS/CLP "Aspiration toxicity Category 1, H304".

Data from experimental exposure of human volunteers with a toluene show that dizziness and sleepiness are experienced at air levels < 20 mg/L. Therefore, low benzene naphtha streams that contain ≥20 % toluene will justify classification R67 “Vapours may cause drowsiness” under Dir 67/548/EEC and Category 3 H336 under GHS/CLP.