Ammonium 7-(2,6-dimethyl-8-(2,2-dimethylbutyryloxy)-1,2,6,7,8,8a-hexahydro-1-naphthyl)-3,5-dihydroxyheptanoate

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2nd June 2011 to 8th August 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 314 B (Simulation Tests to Assess the Biodegradability of Chemicals in Wastewater. B: Biodegradation in Activated Sludge)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Ammonium 7-(2,6-dimethyl-8-(2,2-dimethylbutyryloxy)-1,2,6,7,8,8a-hexahydro-1-naphthyl)-3,5-dihydroxyheptanoate

EC Number:

404-520-2

EC Name:

Ammonium 7-(2,6-dimethyl-8-(2,2-dimethylbutyryloxy)-1,2,6,7,8,8a-hexahydro-1-naphthyl)-3,5-dihydroxyheptanoate

Cas Number:

139893-43-9

Molecular formula:

C25 H43 O6 N

IUPAC Name:

ammonium 7-{8-[(2,2-dimethylbutanoyl)oxy]-2,6-dimethyl-1,2,6,7,8,8a-hexahydronaphthalen-1-yl}-3,5-dihydroxyheptanoate

Test material form:

solid: particulate/powder

Radiolabelling:

yes

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

The activated sludge was collected from Worlingworth sewage treatment plant on 1 June 2011, which treats predominantly domestic wastewater. The sludge sample was sieved (2 mm sieve) then aerated in the laboratory until addition to the test system within 1 day of its collection.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

1 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Individual systems containing 2L of activated sludge were contained in 4L capacity glass vessels. There were two test systems, one biotic and one abiotic. The abiotic control was autoclaved for 90 minutes at 121°C to serve as "inactivated sludge". After cooling, the abiotic control received 0.2 g of mercuric chloride to sterilize the sludge solution with a final concentration of 0.1 g/L.
The glass vessels were capped with a silicone stopper containing a sampling tube and contain a Teflon®-coated stir bar. Each vessel had an inlet and outlet tube via silicone stopper for air exchange.
The biotic and abiotic test vessels were agitated and aerated under similar conditions using stir plates, magnetic stir bars and air sparging (approximately 60 ml/minute). The mixing and aeration were sufficient to suspend the solids in the test solution and achieve a dissolved oxygen above 2.0 mg O2/L, but not so high as to draw a vortex or cause foaming. Test vessels were incubated in an environmental chamber at 22 ± 2 ºC in darkness. Prior to the addition of the test substance, the dissolved oxygen concentration of the biotic sludge was determined.

Results and discussion

Mean total recovery

Mean total recovery 1

Compartment:

biologically active treatment at end of test

% Recovery:

54.1

St. dev.:

0

Mean total recovery 2

Compartment:

abiotic control measured at end of test

% Recovery:

58.6

St. dev.:

0

% Degradation

Key result

% Degr.:

0.4

St. dev.:

0

Parameter:

radiochem. meas.

Sampling time:

28 d

Remarks on result:

other: completed

Half-life of parent compound / 50% disappearance time (DT50)

Half-life of parent compound / 50% disappearance time (DT50) 1

Key result

Compartment:

biologically active treatment at end of test

DT50:

5.37 d

St. dev.:

0

Type:

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

Temp.:

22 °C

Half-life of parent compound / 50% disappearance time (DT50) 2

Compartment:

abiotic control measured at end of test

DT50:

30.7 d

St. dev.:

0

Type:

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

Temp.:

22 °C

Transformation products:

no

Applicant's summary and conclusion

Validity criteria

Validity criteria fulfilled:

not specified

Conclusions:

Simvastatin ammonium salt degraded in biotic and abiotic sludge at 22°C with a DT50 of 5.37 and 30.7 days respectively.
Less degradation and mineralisation occurred in the abiotic sludge over the 28 day incubation period. This demonstrated that microbial action was the main mechanism for degradation under aerobic conditions.

Executive summary:

The route and rate of degradation of simvastatin ammonium salt were studied in biotic and abiotic sludge in the laboratory under aerobic conditions in a closed system.
Biotic and abiotic sludge samples were treated with [14C]-simvastatin ammonium salt at a nominal rate of 1 mg/L. The samples were incubated under aerobic conditions in the dark at about 22°C for a period of up to 28 days after treatment. The amounts of evolved and dissolved CO2 were measured over the incubation period for biotic and abiotic sludge. Mixed liquor suspended solids (MLSS) extracts of biotic and abiotic sludge were analysed by HPLC. The overall recoveries of applied radioactivity (AR) from biotic and abiotic MLSS samples were in the range 77.2% - 103.6% AR and 68.8% - 104.4% AR, respectively.
In the biotic sludge, extractable radioactivity declined with time, from 91.4% AR at 30 minutes to 54.1% AR after 28 days. There were corresponding increases with time in non-extractable radioactivity (up to 44.6% AR after 28 days). Over the 28 day incubation period the amounts of dissolved CO2 were up to ≤3.3% AR and the evolved CO2 had reached 3.7% AR after 28 days.
The amount of simvastatin ammonium salt declined, in the biotic sludge, from 84.5% AR at 30 minutes to 0.4% AR at 21 days and was not detected at 28 days. An unidentified component D increased to 17.0% AR after 28 days. The remaining unknown components were each ≤8.7% AR.
In the abiotic sludge, extractable radioactivity declined with time, from 94.0% AR at 1 hour to 58.6% AR after 28 days. There were corresponding increases with time in non-extractable radioactivity (up to 30.3% AR). Over the 28 day incubation period the amounts of dissolved CO2 were up to ≤1.4% AR and the no significant quantity of evolved CO2 detected after 28 days.
Simvastatin ammonium salt was the major component at all times in the abiotic sludge and declined from 88.7% AR at 1 hour to 45.8% AR at 28 days. Any unknown components were each ≤5.0% AR.
The DT50 for the degradation of simvastatin ammonium salt in biotic and abiotic sludge at 22oC was 5.37 and 30.7 days respectively.