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Environmental fate & pathways

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Description of key information

Biodegradation in water

Biodegradation study was conducted for evaluating the percentage biodegradability of test substance 2,3-dimethylphenol (CAS no. 526 -75 -0) under aerobic conditions (E. H. Snider and F. S. Manning, 1982). Activated sludge was used as a test inoculum. The organic analyses in the study were performed by gas chromatography / mass spectrometry (GC/MS) on methylene chloride extracts of the wastewater samples. Three extracts were collected--a neutral extract, an acid extract, and a base extract. Water samples extracted and analyzed included the raw wastewater after dissolved air flotation (DAF) treatment, effluent from activated sludge (AS) treatment, and effluent from activated carbon (AC) columns.The percentage degradation of test substance was determined to be 99.98% in 4 days. Thus, based on percentage degradation, test chemical 2, 3-Dimethy phenol was considered to be readily biodegradable in nature.

Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound 2,3-dimethylphenol (CAS No. 526 -75 -0). If released in to the environment, 25.1% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 2,3-dimethylphenol in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 2,3-dimethylphenol in sediment is estimated to be 135 days (3240 hrs).  However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.496%), indicates that 2,3-dimethylphenol is not persistent in sediment.

Biodegradation in soil

The half-life period of 2,3-dimethylphenol (CAS No. 526 -75 -0) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2017). If released into the environment, 74.1% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 2,3-dimethylphenol in soil is estimated to be 30 days (720 hrs). Based on this half-life value of 2,3-dimethylphenol, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Bioaccumulation: aquatic / sediment

From authorative database HSDB, a BCF of 57 was calculated for 2,3dimethylphenol, using an estimated log Kow of 2.61and a regression derived equation.This BCF suggests the potential for bioconcentration in aquatic organisms is moderate.

Adsorption / desorption

The Adsorption Coefficient of test substance 2,3-dimethylphenol (526-75-0) was determined as per the HPLC method (OECD Guideline-121). The Log Koc value was determined to be 1.759 ± 0.001 at 25°C. Thus based on the result it is concluded that the test substance 2,3-dimethylphenol (526-75-0) has a low sorption to soil and sediment and therefore has  moderate migration potential to ground water.

Additional information

Biodegradation in water

Various experimental key and supporting studies for the target compound 2,3-Dimethylphenol (CAS No. 526 -75 -0) were reviewed for the biodegradation end point which are summarized as below:

 

In an experimental key study from peer reviewed journal (E. H. Snider and F. S. Manning, 1982) for target chemical2,3-Dimethylphenol(CAS No. 526-75-0), biodegradation experiment was conducted for evaluating the percentage biodegradability of test substance 2,3-dimethylphenol under aerobic conditions. Activated sludge was used as a test inoculum. The organic analyses in the study were performed by gas chromatography / mass spectrometry (GC/MS) on methylene chloride extracts of the wastewater samples. Three extracts were collected--a neutral extract, an acid extract, and a base extract. Water samples extracted and analyzed included the raw wastewater after dissolved air flotation (DAF) treatment, effluent from activated sludge (AS) treatment, and effluent from activated carbon (AC) columns. The percentage degradation of test substance was determined to be 99.98% in 4 days. Thus, based on percentage degradation, test chemical 2, 3-Dimethy phenol was considered to be readily biodegradable in nature.

 

In a supporting biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test substance 2,3-dimethylphenol (CAS no. 526-75-0) (HSDB, 2016 and SRC PhysProp database, 2017). Activated sludge which is acclimated for a period of 2 days was used as a test inoculum for the study. Initial test substance conc. used for the study was 200 mg/l. The percentage degradation of test substance was determined to be 95.5% degradation by COD removal parameter after 5 days. Thus, based on percentage degradation,2,3-dimethylphenolis considered to be readily biodegradable in nature.

 

Another supporting data from peer reviewed journal (JAMES G. MUELLER et. al, 1991) for the target chemical 2,3 -Dimethylphenol (CAS No. 526-75-0),biodegradation study was carried out for 14 days for evaluating the percentage biodegradability of test substance 2,3 -dimethylphenol. Micro-organism was used as a test inoculum isolated from surface soil which was freshly obtained from the American Creosote Works site. Microbial inoculum was prepared by mixing 25 g of creosote-contaminated surface soil (17) freshly obtained from the American Creosote Works site with 100 ml of 2.5 mM phosphate buffer (pH 7). After being mixed well, the suspension was centrifuged (2,500 rpm, 10 min) to remove larger soil particles. The resultant supernatant was decanted and used as a source of indigenous, "creosote-adapted" microorganisms for the ground water medium (GWM).Ground water medium (GWM) was used for the study. For the biodegradation study, approximately 400 liters of groundwater contaminated with creosote and PCP was recovered from an on-site sampling well. Groundwater was removed from a depth of 7 m through Teflon-coated Bev-a-line tubing (15 mm inner diameter) by means of an electric pump. Groundwater was delivered directly into two freshly rinsed, 208-liter steel drums (DOT-17E) and stored on site for ancillary testing. Five subsamples (1.0 liter) 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 chemical2,3,5-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 analyzed 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 chemical 2,3-dimethylphenolcan be considered to be readily biodegradable nature.

 

In an additional supporting data from secondary source (P.C. Singer et. al; 1978) for the target chemical 2,3 -Dimethylphenol (CAS No. 526-75-0), preliminary biodegradability screening test was conducted for 20 days for evaluating the percentage biodegradability of test substance 2,3-dimethylphenol. Domestic sewage was used as a test inoculum was obtained from the Chapel Hill sewage treatment plant. The test compound were added to duplicate, acid-washed, 300 ml BOD bottles at concentration of approximately 5 mg/l. 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 65°F for 20 days. Oxygen uptake 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 91% by O₂uptake parameter in 20 days. Thus, based on percentage degradation, test chemical 2,3-dimethylphenol was considered to be readily biodegradable in nature.

 

Another biodegradation study was conducted according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) for evaluating the percentage biodegradability of test substance 2,3 -dimethylphenol (CAS no. 526 -75 -0) (Kondo, M et. al; 1988). Initial test substance conc. used in the study was 20 mg/l. Namely, a water, acetone or DMSO solution (0.1 ml) of the test chemicals was added to a mixture of river/sea water (4.9 ml) from an unpolluted area and an autoclaved solution (5.0ml) of 0.2% peptone in a sterile test tube with a tight plug. After sealed with film and fixed at an angle of 30°in a dark box, the test tubes were incubated at 30°C and shaked at 120rpm. Inoculum used for the study was mixed culture obtained from different sources (Sea water from Enoshima Beach and River water from Tama River). The percentage degradation of test chemical in river and sea water was determined to be 100 and 54% by BOD parameter in 3 days. Thus, based on percentage degradation, 2,3 -dimethylphenol is considered to be readily biodegradable in nature.

 

On the basis of above results for target chemical 2,3-Dimethylphenol(from peer reviewed journal, authoritative database HSDB and secondary source), it can be concluded that the test substance2,3-Dimethylphenolcan be considered to be readily biodegradable in nature.

  

Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound 2,3-dimethylphenol (CAS No. 526 -75 -0). If released in to the environment, 25.1% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 2,3-dimethylphenol in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 2,3-dimethylphenol in sediment is estimated to be 135 days (3240 hrs).  However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.496%), indicates that 2,3-dimethylphenol is not persistent in sediment.

Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound 2,3-dimethylphenol (CAS No. 526 -75 -0). If released in to the environment, 25.1% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 2,3-dimethylphenol in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 2,3-dimethylphenol in sediment is estimated to be 135 days (3240 hrs).  However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.496%), indicates that 2,3-dimethylphenol is not persistent in sediment.

Biodegradation in soil

The half-life period of 2,3-dimethylphenol (CAS No. 526 -75 -0) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2017). If released into the environment, 74.1% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 2,3-dimethylphenol in soil is estimated to be 30 days (720 hrs). Based on this half-life value of 2,3-dimethylphenol, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

On the basis of available information, the test substance 2,3 -Dimethylphenol can be considered to be readily biodegradable in nature.

Bioaccumulation: aquatic / sediment

Four studies including experimental data from authorative database and predicted data from validated models for bioaccumulation (BCF) endpoint of target chemical 2,3-dimethylphenol (Cas no. 526-75-0) were summarized as follows:  

 

First study from experimental data for target chemical (Cas no. 526-75 -0) which suggest a BCF of 57 was calculated for 2,3 dimethylphenol, using an estimated log Kow of 2.61and a regression derived equation. This BCF suggests the potential for bioconcentration in aquatic organisms is moderate. (HSDB database by US EPA; 2017)

 

Above experimental result supported by prediction using BCFBAF (v3.00) model and PBT profiler which indicate the estimated bio concentration factor (BCF) for 2,3dimethylphenol is 20.1 L/kg wet-wt which does not exceed the bioconcentration threshold of 2000.Thus it is concluded that 2,3-dimethylphenol is not expected to bio accumulate in the aquatic environment.

 

Above prediction is further assisted by Scifinder database wherein the Bioconcentration factor (BCF) for target chemical 2,3-dimethylphenol was predicted to be 38.0 at pH range 1-8, 36.6 at pH 9 and 27.6 at pH 10 at temperature 25 deg.C. Based on the BCF concentration at all range of pH it is concluded that the test chemical 2,3-dimethylphenol is non bioaccumulative in nature as it does not exceed the BCF criteria of 2000.

 

And data from Chemspider - ACD/PhysChem Suite prediction model also indicate the Bioconcentration factor (BCF) for target chemical 2,3-dimethylphenol was to be estimated as 36.56 at pH 5.5 and 7.4 at temperature 25 deg.C. Based on the BCF concentration at two different pH concluded that the test chemical 2,3-dimethylphenol is non bioaccumulative in nature as it does not exceed the BCF criteria of 2000.

 

Thus based on all available studies for bioaccumulation endpoint concluded that the test substance 2, 3-dimethylphenol (Cas no. 526-75-0) is expected to be non Bioaccumulative in aquatic environment.

Adsorption / desorption

Various studies including experimental studies and studiy from authorative database for adsorption (KOC) endpoint of target chemical 2,3-dimethylphenol (Cas no. 526-75-0) were summarized as follows:

In an experimental study,the adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals. The solutions of the test substance and reference substances were prepared in appropriate solventsA test item solution was prepared by accurately weighing 5 mg of test item and diluted with Acetonitrile up to 10 ml. Thus, the test solution concentration was 500 mg/l. The pH of test substance was 6.6.Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances Xylene, Ethylbenzene, Toluene, Naphthalene, Phenol, phenanthrene were chosen having Koc value range from 1.32 to 4.09.The Log Koc value of test chemical was determined to be 1.759 ± 0.001dimensionless at 25°C.This log Koc value indicates that the substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

In another study from authorative database (HSDB by US EPA; 2017) indicate the Koc of 2,3-dimethylphenol as 630,using a structure estimation method based on molecular connectivity indices. This estimated Koc value suggests that 2,3dimethylphenol is expected to have low mobility in soil.

Thus all available studies for adsorption endpoint concluded that the test substance 2,3-dimethylphenol (Cas no. 526-75-0) is expected to have low mobility in soil and sediment compartment.