Reaction mass of divinylbenzene and ethylstyrene

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)

Deviations:

yes

Remarks:

A total plate count on surface water (BCW-041913) was not determined

GLP compliance:

yes

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment

Duration of test (contact time):

60 d

Initial conc.:

50 µg/L

Based on:

test mat.

Initial conc.:

500 µg/L

Based on:

test mat.

Initial conc.:

1 500 µg/L

Based on:

test mat.

Key result

Compartment:

water

DT50:

12.64 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: [14C] 1,3 EVB @ 500 ug/L DT90 41.99 days

Key result

Compartment:

other: surface water-sediment mixture

DT50:

8.849 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: [14C] 1,3 EVB@ 500 ug/L DT90 29.4 d

Compartment:

other: surface water-sediment mixture

DT50:

13.86 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: [14C] 1,3 EVB @ 50 ug/L DT90 46.05 d

Compartment:

other: surface water-sediment mixture

DT50:

31.37 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: [14C] 1,3 EVB+DVB-55 @ 50 ug/L DT90 104.2 d

Compartment:

water

DT50:

10.39 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: [14C] 1,4 DVB @ 1500 ug/L DT90 34.5 d

Compartment:

other: surface water-sediment mixture

DT50:

20.57 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: [14C] 1,4 DVB @ 1500 ug/L DT90 68.35

Compartment:

other: surface water-sediment mixture

DT50:

3.836 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: [14C] 1,4 DVB @ 50 ug/L DT90 12.74

Other kinetic parameters:

first order rate constant

Transformation products:

not specified

The disappearance of [¹⁴C]1,3 EVB and [¹⁴C]1,4 DVB from surface water and surface water-sediment systems was associated with the appearance up to eight more polar radiolabeled degradation products in addition to¹⁴CO₂.

Mineralization to¹⁴CO₂was observed in the surface water-sediment systems dosed with [¹⁴C]1,3 EVB. The¹⁴CO₂ production reached a maximum of 19.8 to 67.7% of the initial activity from test systems dosed at 50 and 500µg/L, respectively, and was confirmed by barium chloride precipitation.

 

Minimal mineralization to¹⁴CO₂ was observed in surface water systems dosed with [¹⁴C]1,3 EVB (≤3% of applied radioactivity), and surface water-sediment systems dosed with a combination of [¹⁴C]1,3 EVB and DVB55 (<1% of applied radioactivity).

 

The¹⁴CO₂ production in the surface water and surface water-sediment systems dosed with [¹⁴C]1,4 DVB was <2% of applied radioactivity. 

 

The¹⁴CO₂ production in the abiotic surface water and surface water-sediment systems dosed with [¹⁴C]1,4 DVB was <0.2% of applied radioactivity.  

Validity criteria fulfilled:

yes

Conclusions:

Primary degradation of [14C]1,3 EVB and [14C]1,4 DVB to more polar [14C]degradation products occurred in surface water and surface water/sediment mixtures with half-lives ranging from 3.8 to 31.4 days over the test concentration range of 50 to 1500 µg/L. Half-lives for the test materials were shorter in the presence of sediment, likely due to higher concentrations of microorganisms associated with sediments.

Mineralization of [14C]1,3 EVB to 14CO2 reached 19.8 and 67.7% within 49 days at 50 and 500 µg/L, respectively, in the presence of sediment while mineralization was limited in surface water alone (3%). In the presence of non-labeled DVB-55, the half-life of 50 µg/L [14C]1,3 EVB in water/sediment mixtures increased from 17.4 to 34.3 days and mineralization to 14CO2 was limited (<1%). Little mineralization of [14C]1,4 DVB (<1%) occurred in the reaction mixtures under the conditions of the test.

The half-lives for the parent compounds 1,3-EVB and 1,4-DVB are less than the criteria for persistence in surface water (i.e. 40 days in fresh water). Inspection of the tables in the study report listing metabolites as a percentage of applied radioactivity at each sampling point illustrates an overall progression of multiple metabolites to shorter HPLC retention times over time. In the reverse-phase HPLC assay used in the study, shorter retention times correlate with more polar, water soluble metabolites. The progression to shorter retention times indicates that these metabolites themselves are not persistent, but rather continue to degrade to simpler, more polar compounds.

Efforts were made to structurally characterize transformation products formed during aerobic mineralization of DVB-55 in surface water that represented >10% of the administered radioactive dose. Selected samples were subjected to analysis by GC/MS and LC/MS by Electrospray Ionization in the positive and negative ionization modes (ESI (+/-)), Atmospheric Pressure Chemical Ionization (APCI (+/-)), and Atmospheric Pressure Photo Ionization (APPI). Due to the insufficient amount of mass of the unknown(s), no conclusive identification could be made from the analysis results generated in this study.

Attempts to identify the metabolites using a variety of analytical techniques were unsuccessful due to insufficient amounts of the unknowns available for characterization.

Executive summary:

The study was conducted to evaluate the rate and extent of degradation of a¹⁴C-labeled test substance and its components in surface water-sediment systems. The test substance divinylbenzene (DVB-55) is composed of 55-57% meta and para isomers of divinylbenzene (CAS # 1321-74-0; EC # 215-325-5) and 43-45% meta and para isomers of ethylvinylbenzene (CAS # 28016-30-1; EC # 248-846-1).  Radiolabelled 1,4 divinylbenzene, ([¹⁴C] 1,4 DVB) and 1,3 ethylvinylbenzene([¹⁴C] 1,3 EVB), chosen as representative components of DVB-55, were used to determine both primary degradation and mineralization kinetics and allowed for the detection of any stable degradation products formed at >10% yield. Incubation of the non-labeled components of DVB-55 with the [¹⁴C] 1,3 EVB in selected reaction mixtures was used to evaluate the impact of the isomers on the degradation kinetics of the radiolabeled test material.

 

Rapid primary degradation of [¹⁴C]1,3 EVB and limited mineralization to¹⁴CO₂ was observed in surface water systems dosed at 500 µg/L. Within 35 days, only 3.3 to 5.2% of [¹⁴C]1,3 EVB remained in replicate microcosms, and was not detected thereafter. The disappearance of the test material was associated with the appearance of multiple polar degradation products. Mineralization of the [¹⁴C]1,3 EVB reached a maximum of 3.0%.

 

Primary degradation of the[¹⁴C]1,3 EVB and more extensive mineralization to ¹⁴CO₂ was observed in the surface water-sediment systems dosed at 50 and 500 µg/L. Within 60 days, only 1.5 to 3.7% of the [¹⁴C]1,3 EVB remained in the systems. The¹⁴CO₂ production reached a maximum of19.8 to 67.7%of applied radioactivity from the surface water-sediment systems dosed at 50 and 500 µg/L, respectively. The more rapid degradation is consistent with the higher concentrations of microorganisms that are typically associated with sediments.

 

Primary degradation rates in surface water-sediment systems dosed with[¹⁴C]1,3 EVB and non-labeled DVB-55 at 50 µg/L were slower than those dosed with [¹⁴C]1,3 EVB alone.  At the end of the study more than 30% of [¹⁴C]1,3 EVB remained in the test mixtures and limited mineralization was observed (<1%).

 

Regression analyses of the percentage of the test substance and total metabolites as a function of time were performed and DT₅₀ and DT₉₀ values were calculated. Half-lives (i.e. DT₅₀values) for [¹⁴C]1,3 EVB ranged from 8.8 to 31.4 days. The calculated half-life for total metabolites decreased dramatically with the addition of sediment to the surface water (from 5.8 × 10¹⁵ to 16.8 days), consistent with the higher concentration of microorganisms present in the sediment as noted above.

 

Primary degradation of [¹⁴C]1,4 DVB and limited mineralization to ¹⁴CO₂ was observed in surface water systems dosed at 1500 µg/L. Within 21 days, 14.7 to 18.1% of [¹⁴C]1,4 DVB remained, and was not detected thereafter. The disappearance of the test material was associated with appearance of multiple polar degradation products.

        

Primary degradation of [¹⁴C]1,4 DVB and limited mineralization to ¹⁴CO₂ was observed in the surface water-sediment systems dosed at 50 and 1500 µg/L. Within 60 days, 3.0 to 3.6% and 23.6 to 22.0% of [¹⁴C]1,4 DVB remained in the systems dosed at 50 and 1500 µg/L, respectively.  

 

Regression analyses of the percentage of the test substance and total metabolites as a function of time were performed and DT₅₀ and DT₉₀ values were calculated. Half-lives (i.e. DT₅₀ values) for [¹⁴C]1,4 DVB ranged from 3.8 to 20.6 days . The calculated half-life for total metabolites again decreased dramatically with the addition of sediment to the surface water (from 5.7×10¹² to 145.4 days), consistent with the higher concentration of microorganisms present in the sediment as noted above.

 

In the abiotic surface water-sediment control mixtures, [¹⁴C]1,4 DVB was present at 80.8 to 85.9% of applied radioactivity at the beginning of the test and declined to a range of non-detected to 48.8% by the end of the test (day 60). In the surface water abiotic control mixtures, [¹⁴C]1,4 DVB was present at 99.2 to 103.0% at the beginning of the test and declined to a range of 87.8 to 89.6% by the end of the test.  The ¹⁴CO₂ production in the abiotic controls was <0.2%. The much slower rates of degradation observed in the abiotic controls confirmed that most of the degradation observed in the viable mixtures was due to biological activity. 

 

To conclude, primary degradation of [¹⁴C]1,3 EVB and [¹⁴C]1,4 DVB to more polar [¹⁴C]degradation products occurred in surface water and surface water/sediment mixtures with half-lives ranging from 3.8 to 31.4 days over the test concentration range of 50 to 1500 µg/L. Half-lives for the test materials were shorter in the presence of sediment, likely due to higher concentrations of microorganisms associated with sediments.  Mineralization of [¹⁴C]1,3 EVB to ¹⁴CO₂ reached 19.8  and 67.7% of applied radioactivity within 49 days at 50 and 500 µg/L, respectively, in the presence of sediment while mineralization was limited in surface water alone (3%). Little mineralization of [¹⁴C]1,4 DVB(<1%) occurred in the reaction mixtures under the conditions of the test.

Efforts were made to structurally characterize transformation products formed during aerobic mineralization of DVB-55 in surface water that represented >10% of the administered radioactive dose. Selected samples were subjected to analysis by GC/MS and LC/MS by Electrospray Ionization in the positive and negative ionization modes (ESI (+/-)), Atmospheric Pressure Chemical Ionization (APCI (+/-)), and Atmospheric Pressure Photo Ionization (APPI). Due to the insufficient amount of mass of the unknown(s), no conclusive identification could be made from the analysis results generated in this study.

 

Attempts to identify the metabolites using a variety of analytical techniques were unsuccessful due to insufficient amounts of the unknowns available for characterization.

Description of key information

A study of biodegradation in surface water/sediment was conducted according to OECD Guideline 309. Primary degradation of [14C]1,3 EVB and [14C]1,4 DVB to more polar [14C] degradation products occurred in surface water and surface water/sediment mixtures with half-lives ranging from 3.8 to 31.4 days over the test concentration range of 50 to 1500 µg/L. Mineralization of [14C]1,3 EVB to14CO2 reached 19.8  and 67.7% of applied radioactivity within 49 days at 50 and 500 µg/L, respectively, in the presence of sediment while mineralization was limited in surface water alone (3%). Little mineralization of [14C]1,4 DVB (<1%) occurred in the reaction mixtures under the conditions of the test. The half-lives for the parent compounds 1,3-EVB and 1,4-DVB are less than the criteria for persistence in surface water (i.e. 40 days in fresh water). Inspection of the tables in the study report listing metabolites as a percentage of applied radioactivity at each sampling point illustrates an overall progression of multiple metabolites to shorter HPLC retention times over time. In the reverse-phase HPLC assay used in the study, shorter retention times correlate with more polar, water soluble metabolites. The progression to shorter retention times indicates that these metabolites themselves are not persistent, but rather continue to degrade to simpler, more polar compounds. Efforts were made to structurally characterize transformation products formed during aerobic mineralization of DVB-55 in surface water that represented >10% of the administered radioactive dose. Selected samples were subjected to analysis by GC/MS and LC/MS by Electrospray Ionization in the positive and negative ionization modes (ESI (+/-)), Atmospheric Pressure Chemical Ionization (APCI (+/-)), and Atmospheric Pressure Photo Ionization (APPI). Due to the insufficient amount of mass of the unknown(s), no conclusive identification could be made from the analysis results generated in this study.  

Additional information

The study was conducted to evaluate the rate and extent of degradation of a14C-labeled test substance and its components in surface water-sediment systems. Radiolabelled 1,4 divinylbenzene, ([14C] 1,4 DVB) and 1,3 ethylvinylbenzene ([14C] 1,3 EVB), chosen as representative components of DVB-55, were used to determine both primary degradation and mineralization kinetics and allowed for the detection of any stable degradation products formed at >10% yield. Incubation of the non-labeled components of DVB-55 with the [14C] 1,3 EVB in selected reaction mixtures was used to evaluate the impact of the isomers on the degradation kinetics of the radiolabeled test material.

 

Primary degradation of [14C]1,3 EVB and [14C]1,4 DVB to more polar [14C] degradation products occurred in surface water and surface water/sediment mixtures with half-lives ranging from 3.8 to 31.4 days over the test concentration range of 50 to 1500 µg/L. Half-lives for the test materials were shorter in the presence of sediment, likely due to higher concentrations of microorganisms associated with sediments. 

 

Mineralization of [14C]1,3 EVB to 14CO2 reached 19.8 and 67.7% within 49 days at 50 and 500 µg/L, respectively, in the presence of sediment while mineralization was limited in surface water alone (3%). In the presence of non-labeled DVB-55, the half-life of 50 µg/L [14C]1,3 EVB in water/sediment mixtures increased from 17.4 to 34.3 days and mineralization to 14CO2 was limited (<1%). Little mineralization of [14C]1,4 DVB (<1%) occurred in the reaction mixtures under the conditions of the test. 

 

The half-lives for the parent compounds 1,3-EVB and 1,4-DVB are less than the criteria for persistence in surface water (i.e. 40 days in fresh water).  Inspection of the tables in the study report listing metabolites as a percentage of applied radioactivity at each sampling point illustrates an overall progression of multiple metabolites to shorter HPLC retention times over time.  In the reverse-phase HPLC assay used in the study, shorter retention times correlate with more polar, water soluble metabolites.  The progression to shorter retention times indicates that these metabolites themselves are not persistent, but rather continue to degrade to simpler, more polar compounds.

 

Efforts were made to structurally characterize transformation products formed during aerobic mineralization of DVB-55 in surface water that represented >10% of the administered radioactive dose. Selected samples were subjected to analysis by GC/MS and LC/MS by Electrospray Ionization in the positive and negative ionization modes (ESI (+/-)), Atmospheric Pressure Chemical Ionization (APCI (+/-)), and Atmospheric Pressure Photo Ionization (APPI). Due to the insufficient amount of mass of the unknown(s), no conclusive identification could be made from the analysis results generated in this study.

 

Attempts to identify the metabolites using a variety of analytical techniques were unsuccessful due to insufficient amounts of the unknowns available for characterization.