Dodecanenitrile

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of Dodecanenitrilefor effects in the environment:

 

The chemical Dodecanenitrile (CAS no. 2437-25-4) is used as a flavour and fragrance agent. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled forDodecanenitrile. 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

In an experimental key study from peer reviewed journal (Jackie Aislabie et. al; 1988), biodegradation experiment was conducted for 45 days for evaluating the percentage biodegradability of test substance Dodecanenitrile (CAS no. 2437-25-4) under aerobic conditions at a temperature of 28°C and pH of 7.5, respectively. A bacterial strain Pseudomonas fluorescens was used as a test inoculum isolated from the undecanenitrile broth platings and identified by using Rapid NFT Strips (API Systems S.A.) and also isolated directly from the original enrichment culture by plating onto 0.1 strength Trypticase soy broth (BBL Microbiology Systems) solidified with purified agar (Difco). It was identified as a strain of Pseudomonas aeruginosa by using the Rapid NFT Strips.Pseudomonas fluorescens strain was grown in nitrogen-free medium with 0.1% glucose and 1% shale oil (identical conditions as the parent enrichment culture with the shale oil as the sole nitrogen but not the sole carbon source) or Bushnell-Haas medium with 0.3% shale oil (shale oil as the sole carbon but not the sole nitrogen source). Several soil sources contaminated with petroleum, including soils from oily-sludge land farming and drill cores, were used as sources of inocula for enrichment cultures.Ten grams of each soil was added to 100 ml of a nitrogen-free medium containing (in grams per liter): MgSO4, 0.2; CaCl2, 0.02; KH2PO4, 1; K2HPO4, 1; FeCl3, 0.05. The pH was adjusted to 7.5, and the medium was then autoclaved. After sterilization the medium was amended with a sterile glucose solution to give a final concentration of 0.1% (wt/vol) and shale oil to give a concentration of 1% (wt/vol).The shale oil was thus the sole source of nitrogen but not the sole source of carbon for these enrichments.The enrichments were incubated at 28°C on a rotary shaker at 200 rpm. The enrichment cultures have been maintained by monthly transfers into fresh medium. Initial test substance concentration used for the study was1000 mg/l.After 7 days of incubation with the aliphatic nitriles as substrates, hexamethylbenzene (HMB) was added as an internal standard, and the nitriles were recovered from the broth by extraction with methylene chloride.The ability of bacterium to utilize these individual nitriles as sole nitrogen and carbon sources was determined by gas-liquid chromatography with a flame ionization detector and the chromatographic conditions.The percentage degradation of test substance Dodecanenitrile was determined to be 100% after a period of 3 days. Thus, based on percentage degradation, Dodecanenitrile is considered to be readily biodegradable in nature.

 

Another biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test substance Dodecanenitrile (CAS no. 2437-25-4) (from secondary source U.S. Environmental Protection Agency, 2012 and HPVIS, 2017). The study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) under aerobic conditions. Activated sludge, domestic was used as a test inoculum for the study. The percentage degradation of test substance Dodecanenitrile was determined to be15% by ThOD parameter in 28 days. Thus, based on percentage degradation, Dodecanenitrile is considered to be not readily biodegradable in nature.

 

In a prediction using the Estimation Programs Interface Suite (EPI suite, 2017), the biodegradation potential of the test compound Dodecanenitrile (CAS no. 2437 -25 -4) in the presence of mixed populations of environmental microorganisms was estimated. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical Dodecanenitrile is expected to be readily biodegradable.  

 

Experimental results from the similar substances (CAS: 2243-27-8 and 2244-07-7) also indicate that they are readily biodegradable.

 

Environmental fate

According to the fugacity model levels III, the most likely environmental fate for this test chemical is soil (i.e.estimated to 78.9%). In soil,Dodecanenitrilewas expected to have negligible to slow mobility based upon a Log KOC value ranging from 3.243 to 4.161. 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, 17.1% of the chemical will partition into water according to the Mackay fugacity model level III in EPI suite version 4.1 (2017). However, the half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and 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 2% when estimated by EPI Suite version 4.1).

 

In a supporting study from secondary source Robust Summary & Test Plans: Fatty Nitrogen Derived Nitriles Category: Robust Summary, 2003), half-life of the chemicalDodecanenitrile(CAS No: 12437-25-4) in water, sediment and soil was estimated by using Mackay EQC Fugacity Level III. The following values has been used in the Mackay EQC Fugacity Level III for the estimating the half-life value. They are vapour pressure: 0.00628 mm Hg, log Kow: 4.9 and Henry’s law constant: 0.000848 atm-m3/mole, respectively. If released into the environment, 66.8% of the chemical will partition into water according to the Mackay EQC Fugacity Level III and the half-life period ofDodecanenitrileis estimated to be 15 days (360 hrs) in water; 60 days (1440 hrs) in sediment and 15 days (360 hrs) in soil. The half-life (as estimated by Mackay EQC Fugacity Level III) indicates that the chemicalDodecanenitrileis not persistent all three compartments.

 

Hence it has been concluded that chemical Dodecanenitrile is not persistent in nature.

 

Bioaccumulation assessment

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

 

The estimated BCF value from authoritative database was determined to be in the range from 2450 to 4577.26, respectively and the octanol water partition coefficient of the test chemical is 4.77 which is greater than the threshold of 4.5. If this chemical is released into the aquatic environment, there should be a moderate risk for the chemical to bioaccumulate in fish and food chains.

 

Hence, it has been concluded that the chemical Dodecanenitrile is bioaccumulative (B) 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 not classified for carcinogenicity, mutagenicity 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

All of the available short-term eco-toxicity estimations for fish, invertebrates and algae for the substance indicates the LC50/EC50 value to be in the range 0.059 – 2.344 mg/L and on the basis of long term eco-toxicity data for fish and aquatic invertebrates, the NOEC value was determined to be 0.065 and 0.071 mg/l, respectively. These value suggest that the substance is likely to be hazardous to Aquatic organisms at environmentally relevant concentrations and can be considered to be classified in ‘Aquatic Acute Category 1’ and ‘Aquatic Chronic Category 2’ as per the CLP regulation.

 

By speculation, long-term NOEC for aquatic organisms can be expected for the substance at concentration below 0.01 mg/L based on the data mentioned above

 

The chemical was therefore considered as hazardous to aquatic environments as per the criteria set out in Annex XIII.

 

Conclusion

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