Octa-1,7-diene

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The PBT Assessment for 1,7-octadiene is based on the criteria set out in the "Guidance on information requirements and chemical safety assessment, Chapter R. 11: PBT Assessment" (ECHA 2012).

Persistence:

For 1,7-octadiene a study on "readily biodegradability" according to the ISO Draft (BOD Test for Insoluble Substances) was conducted resulting in 53% biodegradation after 28 days based on O2-consumption. Based on this result the substance has to be considered as not readily biodegradable. However according to ECHA Guidance R7b, “Biodegradation above 20% of theoretical (measured as BOD, DOC removal or COD) may be regarded as evidence of inherent, primary biodegradability, whereas biodegradation above 70% of theoretical (measured as BOD, DOC removal or COD) may be regarded as evidence of inherent, ultimate biodegradability.”

Furthermore, as 1,7-octadiene is very volatile with a vapour pressure of 18 hPa at 20°C, testing of the substance is difficult and may lead to an overestimation of risk due to substance loss. Thus, in addition to the experimental results described, a QSAR-calculation was performed (BIOWIN v4.00). Based on this calculation the substance could be considered as readily biodegradable.

According to ECHA Guidance R11, QSAR estimates may be used for preliminary identification of substances with a potential for persistency. The guidance document states that the combined results of the three freely available estimation models BIOWIN 2 and BIOWIN 3 or BIOWIN 6 and BIOWIN 3 may be used. According to the recommendation the substance can be regarded as not persistent in case BIOWIN 2 indicates fast biodegradation and BIOWIN 3 led to a degradation < months or if BIOWIN 6 indicates fast biodegradation and BIOWIN 3 led to a degradation < months. For 1,7-octadiene the mentioned criteria for both combinations are met.

 

Thus, concluding from the available information, 1,7-octadiene does not meet the screening criterion for persistency and it is not considered to be persistent (P) or very persistent (vP).

Bioaccumulation:

1,7-Octadiene has a log Kow of 4.0 (calculation with KOWWIN v1.67). Thus, the test substance does not meet the screening criterion for bioaccumulation and is not considered to be bioaccumulative (B) or very bioaccumulative (vB).

Toxicity:

Calculation of toxicity of 1,7-octadiene on algae by using a QSAR-model resulted in an EC50 of 0.66 mg/L based on growth rate. According to "Guidance on information requirements and chemical safety assessment, Chapter R. 11: PBT Assessment" (ECHA 2012)., Table R.11-4, 1,7-octadiene is to be considered as presumably not T.

Moreover, based on the available data 1,7-octadiene is not classified as CMR and for chronic toxicity according to Directive 67/548/EEC and Regulation (EC) No. 1272/2008 (2nd ATP). However, an OECD 408 and OECD 414 study is proposed. In this respect the toxicity assessment (T criterion) is interim and may need to be revised depending on the outcome of new studies.