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Description of key information

As C5 non-cyclics streams are inherently of unknown and variable composition, and taking into consideration the possible percentages of components which are acutely toxic it is proposed that all streams are classified as harmful via oral and dermal exposure routes.  
Two of the component substances, 2-methyl-2-butene and cyclopentene, are classified as harmful under DSD via the oral route and cyclopentene is also classified as harmful via the dermal route. 2-Methyl-2- butene vapour causes drowsiness and dizziness. Due to their low kinematic viscosity C5 non-cyclics represent an aspiration hazard.

Key value for chemical safety assessment

Additional information

Acute oral and inhalation studies are available for the non-cyclic C5 category stream, CAS No. 92128-68-2 (BASF, 1990).  In the rat, the acute oral LD50 was >2000 mg/kg and the inhalation LC50 was >5200 mg/m3.

Data are also available for the marker substances isoprene and for penta-1,3-diene (1,3 -pentadiene) which is a major component in C5 non cyclics stream CAS No. 68477-35-0. Neither of these substances is classified under DSD.

Isoprene has a low potential for acute toxicity. In rats and mice, the oral LD50 of isoprene is in the range of 2,043 to 2,210 mg/kg. The 4-hour rat LC50 is 64,620 ppm (180,037 mg/m3) and the 2-hour mouse LC50 is 56,363 ppm (157,033 mg/m3) (OECD SIDS Isoprene, 2005).

1,3-pentadiene has an oral LD50 in rats of less than 5000 mg/kg (EBSI, 1991a). Seven rats died during the study (3/5 males and 4/5 females). The 4 hour LC50 of 1,3-pentadiene in SD rats is greater than 20917 ppm (58200 mg/m3) (OECD SIDS 1,3-pentadiene, 2005). In mice the 4-hour LC50 in mice is less than 20917 ppm. All the mice were dead by the end of the second hour of exposure. The rabbit dermal LD50 is greater than 3200 mg/kg; there were no deaths at this dose (OECD SIDS 1,3-pentadiene, 2005).

Two potential component substances are classified as Harmful under DSD for acute toxicity, and 2 methyl-2 -butene vapour may cause drowsiness.

Inhaled 2-methyl-2- butene can produce central nervous system depression which is reversible following cessation of exposures is in the range of 1000 to 1700 mg/kg (Shell Research Centre, 1980) and warrants classification as harmful (DSD - Xn, R22; CLP– Cat 4 H302).  No classification is warranted for acute inhalation and dermal toxicity.

Cyclopentene has an LD50 of 1592 mg/kg bw by the oral route and an LD50 of 1183 mg/kg bw by the dermal route in rats (Smyth et al., 1969) leading to classification under DSD as harmful R22 and R21 respectively. It is not classified as harmful via inhalation.

Aspiration is a known hazard of hydrocarbons. The non-cyclic C5 category stream (CAS No 92128-68-2) has a kinematic viscosity of 0.36 mm2/s at 20oC. Classification is based on values at 40oC but in the absence of any other information this is considered to be below the cut off values of 7mm2/s for DSD and of 20.5 mm2/s for hydrocarbons under CLP and therefore classification is warranted.

Justification for classification or non-classification

There is data on only one C5 non-cyclics stream which is not acutely toxic by the oral or inhalation route. However streams in this category contain variable amounts of several component and marker substances which are classified as acutely toxic. For classification under DPD and CLP the relative proportions of specific component substances must be taken into consideration. These are 2-methyl-2-butene and cyclopentene which both warrant classification as harmful if swallowed, R22 under DSD. Cyclopentene also warrants classification as harmful in contact with skin, R21 under DSD.

As C5 non-cyclics streams are inherently of unknown and variable composition, and taking into consideration the possible percentages of these components it is proposed that all streams are classified as harmful via oral and dermal exposure (Xn, R21/R22) corresponding with CLP classification Cat 4 H302 and H312.

Data from experimental exposure of human volunteers with a number of component substances show that dizziness and sleepiness are experienced at air levels <20 mg/L which justifies classification R67 under DPD with corresponding classification as STOT-SE Category 3 H336 under CLP.

The kinematic viscosity of a representative C5 non-cyclics stream justifies classification of all streams as harmful with a mandatory label of Xn, R65, under DSD and, under CLP, STOT-SE Category 1, H304.