2,3,5-trimethylphenol

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of 2,3,5-trimethylphenol for effects in the environment:

 

The chemical of 2,3,5-trimethylphenol (CAS no 697-82-5) is used as for chemical synthesis and as a laboratory agent . The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for 2,3,5-trimethylphenol. 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

Various experimental data for the target compound 2,3,5-trimethylphenol (CAS no. 697-82-5) were reviewed for the biodegradation end point which are summarized as below:

 

In an experimental key study, preliminary screening of biodegradation was carried out for 20 days to evaluating the percentage biodegradability of test substance 2,3,5 –trimethylphenol (CAS no. 697-82-5) (PC. Singer et. al; 1978). Domestic sewage was used as a test inoculum obtained from Chapel Hill sewage treatment plant. Concentration of inoculum i.e., sludge used was 1.5 mg/l and initial test substance conc. used in the study was 5 mg/l, respectively. Test chemical was added to duplicate, acid washed, 300 ml BOD bottles. Dilution water was prepared from water which had been passed through activated carbon and ion exchange columns and then glass-distilled. Standard nutrients were added to the water as was 0.5 mg/l allylthiourea for control of nitrification. The dilution water was seeded with 1.5 mg/l of domestic sewage. The BOD bottles were filled, stoppered and incubated in the dark at 18.33°C (65°F) for 20 days. O2 consumption was measured at various intervals over the 20 day period by means of a Weston and Stack dissolved oxygen meter. The percentage degradation of test substance was determined to be 80% by O2 consumption parameter in 20 days. Thus, based on percentage degradation, 2,3,5 -trimethylphenol is considered to be readily biodegradable in nature.

 

Another study was carried out for 14 days for evaluating the percentage biodegradability of test substance 2,3,5-trimethylphenol (CAS no. 697-82-5) (JAMES G. MUELLER et. al; 1991). Micro-organism was used as a test inoculum isolated from surface soil which was freshly obtained from the American Creosote Works site. Ground water medium (GWM) was used for the study. For the biodegradation study, approximately 400 litres of groundwater contaminated with creosote and PCP was recovered from an on-site sampling well. Five subsamples (1.0 litre) were collected in clean, sterile, 1.0-liter Wheaton bottles fitted with Teflon-lined screw caps and stored on ice for transport to the laboratory. Upon arrival at the laboratory, subsamples were stored in darkness at 2°C for subsequent biodegradation studies, toxicity and teratogenicity testing, and chemical analyses. It contains 2.5 ml of filtered groundwater (passed through a plug of silanized glass wool to remove undissolved solids) plus 12.5 ml of modified Bushnell-Haas medium. Additionally, two clean, sterile, 1.0-liter Wheaton bottles fitted with Teflon-lined screw caps received 200 ml of the same medium. Ground water contains the test chemical 2,3,5-trimethylphenol. Wheaton bottles consist of 200 ml of ground water medium (which contain ground water and modified Bushnell-Haas medium. Duplicate 25 ml samples were immediately extracted for time zero analysis. Flasks were incubated at 30°C with shaking (200 rpm) in the dark for 14 days. Killed-cell controls were prepared for each sampling time point by adding 2.5 ml of a 37% formaldehyde solution to five of the shake flasks containing 25 ml of GWM. After 1, 3, 5, 8, and 14 days of incubation, the entire contents of two active flasks and one killed-cell control flask were separately extracted and analysed by GC for the presence of creosote constituents. These data were compared with those obtained from untreated (non-inoculated) GWM that had been stored at 2°C during the 14-day incubation period. As the limit of detection of test chemical by GC is very low during a period 14 days, test chemical2,3,5-trimethylphenol can be considered to be readily biodegradable in nature. 

 

In a supporting study from peer reviewed journal (HIDESHI YANASE et. al; 1992), biodegradation experimented was conducted for 30 mins for evaluating the percentage biodegradability of test substance 2,3,5 –trimethylphenol (697-82-5). Phenol degrading bacteria (Agrobacterium spp.) was used as a test organism isolated from brine that had just emerged from a natural gas well under the sea near Niigata Prefecture, Japan. Bacterial cells suspended in sterile artificial seawater containing 10% (vol/vol) glycerol were stored frozen at -80°C in plastic vials. Under the storage conditions, the isolates were viable and did not lose phenol degradation activity for at least 2 years. The reaction mixture contained 100 mM MOPS buffer (pH 7.0), 0.1 mM (13.61 mg/l) phenolic compound, and 4.5 mg/mi cells in a total volume of 2.2 ml in a test tube (18 x 180 ram). The reaction occurred at 50°C for 30 mins with reciprocal shaking (230 strokes/rnin).The percentage degradation of test substance was determined to be 21.4 and 20.1% degradation in 30 mins using 10% and 100% seawater, respectively. Thus, based on percentage degradation, 2,3,5 -trimethylphenol is considered to be inherently biodegradable in nature.

 

On the basis of above results for target chemical 2,3,5 -trimethylphenol, it can be concluded that the test substance 2,3,5-trimethylphenol can be expected to be readily biodegradable in nature.

 

Environmental fate

According to the fugacity model levels III, the most likely environmental fate for this test chemical is soil (i.e.estimated to 80.5%). In soil, the substance was expected to have low mobility based upon an experimental Log KOC in therange 2.90.The half-life in soil (75 days estimated by EPI suite) indicates that the chemical is not persistent and the exposure risk to soil dwelling animals is moderate to low.

 

If released in to the environment, 18.6 % 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 (37.5 days as 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 2,3,5-trimethylphenol 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 estimated bioaccumulation factor (BCF) from various databases was determined to be in the range 56-90.4 L/kg wet wt. and the estimated octanol-water partition coefficient for the substance is 3.15 which is less than the threshold of 4.5. 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 does not fulfil 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 estimation for fish, invertebrates and algae for the substance indicates the LC50/EC50 value to be in the range 10-27 mg/L. These value suggest that the substance is likely to be hazardous to Aquatic organisms at environmentally relevant concentrations, but since it is determined to be readily biodegradable in nature, it can be considered to be not classified as per the CLP regulation.

 

There are no available long-term toxicity evaluations for 2,3,5-trimethylphenol. By speculation, long-term NOEC for aquatic organisms were not expected for 2,3,5-trimethylphenol 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 does not fulfil the P, B and T criterion and has therefore not been classified as a PBT compound within Annex XIII.