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Biodegradation in water and sediment: simulation tests

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biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
other: EPA OPPTS 835.3170 (Shake flask die-away test)
GLP compliance:
Oxygen conditions:
Inoculum or test system:
natural water / sediment
Details on source and properties of surface water:
Surface water from 8 locations on 7 rivers and estuaries
Details on source and properties of sediment:
Surficial sediment from 8 locations on 7 rivers and estuaries
Initial conc.:
0.05 - 5 000 µg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
O2 consumption
radiochem. meas.
test mat. analysis
entire system
0.5 - 2.6 d
(pseudo-)first order (= half-life)
Remarks on result:
other: 2 to 8 day lag times
Transformation products:
Details on transformation products:
Metabolites were looked for using HPLC. None were found. The only metabolite quantifiable was CO2.

Summary results are contained in an attached document in a series of tables.

GENERAL RIVER CHARACTERISTICS: Rivers that were sampled had a wide range of characteristics including:

1. Geographical locations (United States vs. Europe),

2. Northern vs. southern climates,

3. Industrial vs. rural locations, and

4. Freshwater vs. estuarine environments.

Water Characteristics (see attached Table 1):

1. BPA was not detected in the river water samples prior to addition of the test compound (LOD for the HPLC method used ranged from 0.050 to 0.100 mg/L),

2. During sampling, river water pH ranged from 6.9 to 8.3,

3. In situ water temperatures ranged from 7.7 to 30.6 C,

4. Dissolved oxygen ranged from 4.8 to 12.4 mg/L,

5. Conductivity measurements ranged from 86 microS/cm to 19,800 microS/cm (the latter for estuarine water),

6. Total dissolved solids ranged from non-detected to 18,500 mg/L,

7. Heterotrophic bacteria in the water samples (standard plate counts) ranged from 2.6E1 to 3.7E4 CFU/mL.

SEDIMENT DESCRIPTIONS (see attached Table 2):

1. Of the nine composite samples (either up or down stream for each river), five were classified as sands, three samples were sandy loams, and one sample was characterized as a loam,

2. Organic carbon content ranged from 0.06 to 2.0%,

3. Heterotrophic bacterial populations ranged from 9.3E4 to 2.1E6 CFU per gram.


1. Measured initial concentrations in die-away tests ranged from 92 to 109% of nominal. Measured initial concentrations in respirometer tests ranged from 75 to 100% of nominal (with one exception, which was 51%).

2. In the die-away tests (Rhine R., Germany and Ohio R., Ohio, USA), lag phases ranged from 2 to 8 days.

3. In the respirometer tests (all rivers), lag phases ranged from 2.8 to 4.4 days and averaged 3.4 days.

4. No degradation of BPA was observed in any killed control, nor were any 14C-metabolites or 14C-CO2 formed.

5. In die-away tests, half-lives ranged from 0.5 to 1.4 days, averaging 0.9 days.

6. In respirometer tests, half-lives ranged from 0.5 to 2.6 days, averaging 1.2 days.

7. In die-away tests, CO2 evolution (as a percentage of ThCO2) reached 65 to 80% of ThCO2

8. In the respirometer tests, O2 demand (as a percent of ThOD) ranged from 75 to 100% (one exception was in downstream water from the Monte Sano Bayou, Louisiana, USA at 53% ThOD). Production of CO2 ranged from 69 to 96% (one exception was in upstream water from the Monte Sano Bayou, Louisiana, USA at 59% ThCO2).

9. Minor differences in lag phases between die-away and respirometer tests was experimentally attributed to sparging the headspace of the respirometer with O2 at test initiation.

10. Based on HPLC-RAM analyses, 14-CO2 was the only metabolite. The remaining 14C was either converted to a complex mixture of polar metabolites or became incorporated into the metabolic cycles of microbes or into new microbial biomass.

11. Biodegradation appeared to be first order as there were no apparent differences in half-lives as a function of BPA concentration.

12. In the low-concentration die-away tests, background concentrations of BPA averaged 30 nanograms/L (LOD ~0.232 nanograms/L).

13. In the low-concentration tests, lag phases were in the range of 0 to 7 days. Rate constants were calculated based on concentrations from day 7 to 28, correcting for abiotic losses observed in killed controls. Half-lives ranged from 2.9 to 5.6 days.


1. The addition of 0.05% sediment (dw) had negligible effect on BPA biodegradation half-lives; however, the addition of 10% sediment significantly enhanced biodegradation.

2. With the 0.05% sediment addition, lag phases ranged from 2.6 to 4.6 days, averaging 3.4 days. Half-lives ranged from 0.7 to 3.4 days, averaging 1.2 days. Degradation was complete by day 11. Without sediment, degradation was complete by day 9. Losses were attributed to biodegradation, not sorption to solids since 90% of 14C was recovered from the dissolved phase in killed controls on day 18 (10% sediment addition).

3. With the 10% sediment addition, the lag phase was essentially eliminated and degradation was complete by day 6. Significant sorption to solids occurred (47% of initial added radioactivity was recovered in combusted sediments). 14C-CO2 (ThCO2) reached only 16% by day 21.

Validity criteria fulfilled:
Executive summary:

Bisphenol A has been shown to be rapidly biodegraded in a series of die-away (measuring loss of parent Bisphenol A) and respirometer (measuring O2 consumption and CO2 evolution) tests using fresh and estuarine water with and without natural sediment collected at several locations in North America and Europe. Aqueous concentrations of Bisphenol A ranged from 0.05 to 5500 microgram/L. Lag phases ranged from 2-8 days. Half-lives ranged from 0.5 to 2.6 days. Microbial consortia capable of rapidly biodegrading appear to be ubiquitous in freshwater and estuarine waters and oxic sediments.

Description of key information

Bisphenol A was found to be rapidly biodegraded by microbial consortia found in many natural waters and sediments, with lag times and half-lives on the order of a few days. 

Key value for chemical safety assessment

Additional information

Biodegradation simulation tests have measured the die-away of Bisphenol A using surface water and sediments collected from rivers, estuaries, and marine waters in North America, Europe, Japan, and Australia. Bisphenol A was found to be rapidly biodegraded by the microbial consortia found in the natural waters and sediments, with lag times and half-lives on the order of a few days. Biodegradation rates are expected to be slower and half-lives longer in tests conducted using lower temperatures and oxygen content. Microbial populations capable of rapidly biodegrading Bisphenol A appear to be ubiquitous in the environment. The biotransformation pathways for Bisphenol A have been defined in several studies.