Phthalic acid

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

according to guideline

Guideline:

other: Biodegradation test of chemical substance by mircoorganisms etc. stipulated in the order Prescribing the Items of the test relating to the new chemical substance (1974)

Principles of method if other than guideline:

This guideline corresponds to 301C, ready biodegradability: modified MITI Test (I) stipulated in the OECD Guidelines for testing of chemicals (May 12, 1981)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

mixture of sewage, soil and natural water

Details on inoculum:

Preparation of activated sludge:

Sludge sampling sites and time
Sampling were made four times in every year at ten places in Japan. Details are included in bibliographic source mentioned above

Mixing of fresh and old activated sludge
5L of the filtrate of the supernatant of an activated sludge in the present use was mixed with 500 mL of the filtrate of the supernatant of a newly collected sludge respectively and the mixture was cultured at 7.0 +- 1.0 under the sufficient aeration (prefiltered open air was used for aeration)

Culture
About 30 minutes after ceasing the aeration to the sludge mixture, supernatant corresponding to about 1/3 of the whole volume was removed. Then the equal volume of dechlorination water was added to the remaining portion and aerated again, followed by addition of synthetic sewage*, concentration of that portion was to be 0.1 (W/V)%. This procedure was repeated once every day. The culturing was carried out at 25+-2°C.
*synthetic sewage: glucose, peptone and monopotassium phosphate were dissolved in dechlorination water respectively. Each concentration of them was to be 5(W/V)% and the solution was adjusted to pH 7.0 +- 1.0 with sodium hydroxide.

Control
During the cultivation, appearance of the supernatant, precipitabiltiy, formation of flock, pH, dissolved oxygen concentration in the solution and temperature were checked and necessary adjustments were made. microflora in the activated sludge was microscopically observed and sludge with no abnormal symptom was used for the test.

Inspection of activity
Activity of the sludge was inspected to use reference substance. And the relation between new and old activated sludge was taken account.

Duration of test (contact time):

2 wk

Initial conc.:

100 mg/L

Based on:

test mat.

Reference substance:

aniline

Remarks:

guaranteed reagent, Showa Chemicals Inc.

Parameter:

% degradation (O2 consumption)

Value:

85.2

Sampling time:

14 d

Interpretation of results:

readily biodegradable

Executive summary:

In a modified MITI test comparable to OECD TG 301 C the biodegradation of phthalic anhydride was investigated (MITI, 1992). After 2 weeks 85 % degradation of the test substance was determined.

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

EU Method C.9 (Biodegradation: Zahn-Wellens Test)

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly industrial (adaptation not specified)

Details on inoculum:

Adaptation phase: 1 day

Duration of test (contact time):

4.5 d

Initial conc.:

1 000 mg/L

Based on:

COD

Initial conc.:

400 mg/L

Based on:

DOC

Details on study design:

- Test temperature and pH value not reported

Reference substance:

diethylene glycol

Parameter:

% degradation (DOC removal)

Value:

> 90

Sampling time:

4.5 d

Details on results:

Kinetic of control substance (in %):
> 90 after 11 day(s)

Interpretation of results:

inherently biodegradable

Executive summary:

The inherent biodegradability of phthalic acid was assessed according to the EU Method C.9 (Biodegradation: Zahn-Wellens Test). Phthalic acid showed > 90% degradation after 4.5 days (Zahn, 1980).

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Basic data given

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic (adaptation not specified)

Initial conc.:

3 mg/L

Based on:

test mat.

Parameter:

% degradation (O2 consumption)

Value:

74

Sampling time:

30 d

Details on results:

Kinetic of test substance (in %):
48 after 5 day(s)
68 after 10 day(s)
64 after 20 day(s)
74 after 30 day(s)

Interpretation of results:

readily biodegradable

Executive summary:

Phthalic acid shows 74% degradation after 30 days in a closed bottle test, which is comparable to the OECD TG 301 D (Bayer, 1973).

Description of key information

Phthalic acid has to be classified as readily biodegradable and is regarded as inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

There is only one study on ready biodegradability of phthalic acid available.

The test was conducted in 1973 according to a national standard method using closed bottles and results in 74% degradation after 30 days, indicating that the substance is readily biodegradable. The structural analogue phthalic anhydride is taken into account to describe the biodegradation behaviour of phthalic acid. Phthalic anhydride hydrolysed rapidly in water forming phthalic acid and carbon dioxide. In a modified MITI test comparable to OECD TG 301 C the biodegradation of phthalic anhydride was investigated (MITI, 1992). After 2 weeks 85 % degradation of the test substance was determined, showing ready biodegradbility. Based on this result, ready biodegradabaility of phthalic acid is considered to be confirmed and the substance has to be classified as readily biodegradable. Inherent biodegradability was documented with a degradation > 90 % within 4.5 days according to EU Method C.9 (Zahn, 1980).