2,2-dimethylbutane

PBT assessment

PBT assessment: overall result

Reference

Name:

2,2-Dimethylbutane - Boundary Composition

Type of composition:

boundary composition of the substance

State / form:

liquid

Reference substance:

2,2-Dimethylbutane - Boundary Composition

PBT status:

the substance is not PBT / vPvB

Justification:

PBT/vPvB criteria and justification 

 

Persistence (P) Assessment: A substance is not considered to be persistent if it can be demonstrated that it has potential to degrade (via photolysis, hydrolysis and/or biodegradation) 

 

There is no key data available for 2,2-dimethylbutane. Key data is available for Hydrocarbons, C6, isoalkanes, <5% n-hexane which have been used to read across to 2,2-dimethylbutane.

 

An OECD 301F Manometric Respirometry test was conducted using C6-C7, n-alkanes, isoalkanes, cyclics C6 aliphatics (Shell, 1997a). The test substance was 98% degraded at the end of 28 days, and 83% degraded at the end of the 10 -day window, and was determined to be readily biodegradable. Therefore, 2,2-dimethylbutane is also assumed to be readily biodegradable.

 

Therefore, 2,2-dimethylbutane does not meet the Persistent (P) or very Persistent (vP) criteria. 

 

Bioaccumulation (B) Assessment: If the substance has a log Kow lower than 4.5 and no specific mechanism of uptake apart from hydrophobic partitioning is known and the possibility for accumulation in other food chains than the aquatic food chain can be ruled out, then the substance can be considered as not B and not vB.

 

2,2 -Dimethylbutane has a reported log Kow of 3.82. Therefore, 2,2-dimethylbutane can be considered not B and not vB.

 

Toxicity (T) Assessment: As 2,2-dimethylbutane is not classified as persistent or bioaccumulative, a toxicity assessment is not required.

 

Human Health Hazards Assessment (T) 

Carcinogenicity: There are no carcinogenicity data available for 2,2-dimethylbutane. Data for the read-across substance n-hexane do not warrant classification for carcinogenicity under Dir 67/548/EEC or GHS/CLP. 

 

Mutagenicity: There are no mutagenicity data available for 2,2-dimethylbutane. Data for the read-across substances n-hexane do not warrant classification for mutagenicity under Dir 67/548/EEC or GHS/CLP. 

 

Reproductive Toxicity: There are no reproductive toxicity data available for 2,2-dimethylbutane. Data for the read-across substances n-hexane warrant a classification of Repr 2. (H361f: suspected of damaging fertility or the unborn child) for reproductive toxicity under the Dir 67/548/EEC or GHS/CLP. 

 

Chronic toxicity: Based on available read across data, 2,2-dimethylbutane is classified STOT RE 2 (H373: may cause damage to organs through prolonged or repeated exposure) for repeated dose toxicity under the Regulation (EC) 1272/2008 on classification, labelling and packaging of substances and mixtures (CLP).

 

Environmental Toxicity (T): There are no ecotoxicity data available for 2,2 -Dimethylbutane. The aquatic toxicity was therefore estimated using the Petrotox computer model (v. 3.06). The lowest predicted acute LL50 value for this range of data is 1.56 mg/L, reported for toxicity to algae. This is greater than the 0.01 mg/l limit for classification as T for the environment.

 

Therefore, 2,2-dimethylbutane is considered T based on the the classification of Repr 2. (H361f: suspected of damaging fertility or the unborn child) and STOT RE 2 (H373: may cause damage to organs through prolonged or repeated exposure).

 

Conclusion of PBT/vPvB assessment 

Based on read-across to Hydrocarbons, C6, isoalkanes, <5% n-hexane 2,2-dimethylbutane can be considered readily biodegradable and therefore is not considered P or vP. Also, based on a reported log Kow of 3.82, 2,2-dimethylbutane is not considered B or vB. As such an assessment for T (toxicity) is not required.2,2-dimethylbutane is not classified as PBT or vP/vB.