Diundecyl phthalate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

yes

Remarks:

(inoculum was pre-adapted to the test substance)

Qualifier:

according to guideline

Guideline:

other: Chemical fate test guidelines. EPA 560/6-82-003

Deviations:

not specified

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 20 mg/L
- Sampling method: The contents of two of the Erlenmeyer flasks were immediately extracted for specific chemical analysis at time zero to determine the percent recovery.
Periodically during the test, base was removed by syringe from the suspended reservoirs for analysis. The appropriate sampling schedule was dictated by the rate of CO2 evolution, which was qualitatively judged from the amount of BaCO3 precipitate present in the absorber.
After sampling, the flasks were sparged for 5 min, and fresh base was added. DUP analysis was conducted on the contents of the remaining duplicate Erlenmeyer flasks at the time when the CO2 evolution results indicated that at least 50% ultimate biodegradation may have occurred. On day 28, the medium was acidified to pH 3 with 20% H2SO4 to convert residual carbonates to CO2. Base was removed for analysis on the next day, and the entire contents of the three CO2 evolution flasks were extracted for specific chemical analysis.

Vehicle:

no

Test organisms (species):

other: Mixture of organically rich fresh soil, activated sludge (domestic) and raw domestic influent sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: The organically rich soil was collected just upland from a freshwater marsh in Berry Park, Syracuse, N.Y. Soil was obtained from a depth of ca. 10 cm and screened through a seive with 2-mm openings. Mixed liquor and raw influent sewage were obtained from the Meadowbrook-Limestone Treatment Plant, Fayetteville, N.Y. This facility treats only domestic wastes. Soil and sewage samples were refrigerated at 4°C and used within 48 h of collection.
- Preparation of inoculum for exposure: The acclimation medium was prepared by adding 1.0 g of organically rich fresh soil, 2.0 ml of fresh aerated mixed liquor obtained from an activated sludge treatment plant, and 50 ml of raw domestic influent sewage with 1 liter of mineral salts medium prepared similarly to that used by Gledhill (Gledhill, W. 1975). This medium was mixed for 15 min and filtered through glass wool. The filtrate was supplemented with 25 mg each of vitamin-free Casamino Acids and yeast extract (Difco Laboratories, Detroit, Mich.) per liter.
1 litre of acclimation medium in a 2-liter Erlenmeyer flask was inoculated with DUP concentration equivalent to 4 mg of carbon at the start of acclimation. The acclimation flasks were sealed and incubated in the dark on a Gyrotory shaker at 120 rpm and 22 ± 2ºC. An additional test compound equivalent to 8 mg of carbon was added on day 7 and again on day 11 during the 14-day acclimation period. At the end of the acclimation period, the contents of all of the acclimation flasks in a set (six test compounds included DUP) were pooled and filtered through glass wool to provide a common inoculum for the primary and ultimate biodegradation tests.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

28 d

Test temperature:

22 ± 2ºC

pH:

7.0 ± 0.2

Nominal and measured concentrations:

20 mg/L (measured)

Details on test conditions:

TEST SYSTEM
- Test vessel: 2-liter Erlenmeyer flasks for DUP analysis and 2-liter CO2 evolution flasks (Ace Glass Co., Vineland, N.J.)
- Material, size, headspace, fill volume: 900 ml of distilled water was added to each of the test flasks, which were then supplemented with 1 ml each of solutions 1, 2, and 3 (see composition below). To begin the tests, a measured weight (nominal 20 mg) of test compound and 100 ml of the pooled acclimation inoculum were added to the flasks.
- No. of vessels per concentration (replicates): Four 2-liter Erlenmeyer flasks for DUP analysis and three 2-liter CO2 evolution flasks.
- No. of vessels per control (replicates): One 2-liter CO2 evolution flask.
- Nitrification inhibitor used (delete if not applicable): none

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The mineral salts medium was prepared by adding 1 ml each of solution 1 (NH4Cl, 35 g/liter; KNO3, 15 g/liter; K2HPO4 31420, 75 g/liter; NaH2PO4 * H2O, 25 g/liter), solution 2 (KCl, 10 g/liter; MgSO4, 20 g/liter; FeSO4 * 7H2O, 1 g/liter), and solution 3 (CaCl2, 5 g/liter; ZnCl2, 0.05 g/liter; MnCl2 * 4H20, 0.5 g/liter; CuCl2, 0.05 g/liter; CoCl2, 0.001 g/liter; H3BO3, 0.001 g/liter; MoO3, 0.0004 g/liter) to 1 liter of aerated distilled water.

OTHER TEST CONDITIONS
- Adjustment of pH: no.
- Photoperiod: continuous darkness

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Biodegradation % based on CO2 evolution.

TEST CONCENTRATIONS
- Test concentrations: 20 mg/L

Reference substance (positive control):

yes

Remarks:

(glucose)

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

other: Readily biodegradability

Details on results:

The NOEC of the test item was determined to be 20 mg/L since the substance degrades well (76% of biodegradation at 28 days based on CO2 evolution).

Results with reference substance (positive control):

- Results with reference substance valid: yes
- Relevant effect levels:
Reference item reached biodegradation (based on CO2 evolution) of 92% (SD =15).
Lag phase was determined to be 0.35 days(SD = 0.70)
Rate constant was determined to be 0.227 days-1 (SD = 0.038)
Half life was determined to be 3.11 days (SD = 0.50)

Validity criteria fulfilled:

yes

Conclusions:

The NOEC (28d) for microorganism toxicity of the test item was determined to be 20 mg/L (based on biodegradation).

Executive summary:

A ready biodegradability test was perfomed according to OECD Guideline 301 B. The test item was incubated for 28 days at a concentration of 20 mg/L under aerobic conditions in a mineral medium with inoculum prepared from soil and sewage microorganisms. The NOEC (28d) of the test item was determined to be 20 mg/L since the substance degraded well (76% of biodegradation at 28 days).

Description of key information

Key study: Test method OECD Guideline 301B (Suggat R H, 1984). The NOEC (28d) was determined to be 20 mg/L (based on no inhibitory effect observed, readily biodegradable substance).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

20 mg/L

Additional information

Key study: A ready biodegradability test was perfomed according to OECD Guideline 301 B. The test item was incubated for 28 days at a concentration of 20 mg/L under aerobic conditions in a mineral medium with inoculum prepared from soil and sewage microorganisms. The NOEC (28d) of the test item was determined to be 20 mg/L since the substance degraded well (76% of biodegradation at 28 days).