3,7-dimethylocta-2,6-dienenitrile

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of 3,7-dimethylocta-2,6-dienenitrile for effects in the environment:

 

The chemical 3,7-dimethylocta-2,6-dienenitrile (CAS no. 5146-66-7) is used as flavour and fragrance agents. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for 3,7-dimethylocta-2,6-dienenitrile. The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models. Here follows a description of the PBT assessment.

 

 

Persistence assessment

The tested substance does not fulfil the P criterion within Annex XIII based on the assessment that here follows:

 

Biotic degradation

Ready biodegradability test was carried out to find biodegradation of chemical 3,7-dimethylocta-2,6-dienenitrile. As inoculum a mixture of (proportion) 1: 1 of municipal sludge from laboratory wastewater treatment plants fed with municipal sewage and sludge from BASF wastewater treatment plant was used. The concentration of the dry substance was 30 mg/l. After 35 days the test substance was degraded up to 100 % (BOD of ThOD).Hence, the test chemical 3,7-dimethylocta-2,6-dienenitrile was found to be biodegradable(10 days window was not covered)with 59% biodegradation in 10 days.

 

Environmental fate

According to the fugacity model levels III, the most likely environmental fate for this test chemical is soil (i.e.estimated to 78.8%). In soil, 3,7-dimethylocta-2,6-dienenitrile was expected to have low mobility based upon a Log KOC of 2.62 - 3.37. The half-life in soil (30 days estimated by EPI suite) indicates that the chemical is not persistent in soil and the exposure risk to soil dwelling animals is moderate to low.

 

If released in to the environment, 20.7 % of the chemical will partition into water according to the Mackay fugacity model level III in EPI suite version 4.1 (2016). However, the half-life (15 days estimated by EPI suite) indicates that the exposure risk to aquatic animals is moderate to low.

Moreover, its persistent characteristic is only observed in the sediment compartment but Fugacity modelling shows that sediment is not an important environmental fate (less than 1% when estimated by EPI Suite version 4.1). Hence it has been concluded that 3,7-dimethylocta-2,6-dienenitrile is not persistent in nature.  

 

 

Bioaccumulation assessment

The tested substance does not fulfil the B criterion within Annex XIII based on the assessment that here follows:

 

The BCF value is estimated as 89.88 at 25ºC (EPI suite version 4.1, 2016) and the experimental log octanol-water partition coefficient (log Kow) was determined to 2.98 -3.47. If this chemical is released into the aquatic environment, there should be a low risk for the chemical to bioaccumulate in fish and food chains.

 

Toxicity assessment

The tested substance fulfils the T criterion within Annex XIII based on the assessment that here follows:

 

Mammals

The tested chemical is regarded to be classified for mutagenicity in Mutgenic Category 1 B as per theHarmonised classification - Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation)

The tested chemical is regarded to be not classified for carcinogenicity, and reprotoxicity, Further, there is no evidence of chronic toxicity, as identified by the classifications STOT (repeated exposure), category 1 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume).

 

Aquatic organisms

The QSAR predictions and experimental EC50/LC50 values were in the range of 2.28 to 7.66 mg/L. Based on the lowest available EC50/LC50,3,7-dimethylocta-2,6-dienenitrilewas suggested to be classified as ‘Aquatic chronic Category 2’.

 

There are no available long-term toxicity evaluations for 3,7-dimethylocta-2,6-dienenitrile. The short-term evaluations for invertebrates and algae report the NOEC values as 1.23mg/L to 3.7 mg/L. By speculation, although the substance is classified as per the CLP criterion, classification for aquatic toxicity will not be applicable as per Annex XIII criteria for all of the tropic levels and the same is based on the above mentioned studies.

 

 

Conclusion

Based on critical, independent and collective evaluation of information summarized herein, the tested compound does not fulfil the P and B criterion but fulfils the T criterion and has therefore not been classified as a PBT compound within Annex XIII.