Chlorothalonil

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: screening test, other

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Deviations:

not specified

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Sludge sampling sites: Sludge sampling were made at the following 10 places in Japan: Fukogawa city sewage plant (Sapporo-shi Hokkaido); Fukashiba industry sewage plant (Kashima-gun Ibaragi); Nakahama city sewage plant (Osaka-shi Osaka); Ochiai city sewage plant (Shinjuku-ku Tokyo); Kitakami river (Ishinomaki-shi Miyagi); Shinano river (Nishikanbara-gun Niigata); Yoshino river (Tokushima-shi Tokushima); Lake Biwa (Otsu-shi Shiga); Hiroshima bay (Hiroshima-shi Hiroshima); Dookai bay (Kitakyushu-shi Fukuoka)
- Sludge sampling time: March, June, September, and December in every year
- Sludge sampling method: For city sewage, returned sludge of sewage plants were collected. For Rivers, lake and sea, surface water and surface soil which is in contact with atmosphere were collected.
- Mixing of fresh and old activated sludge: 5 L 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 pH 7.0 ± 1.0 under the sufficient aeration (Prefiltered open air was used for aeration).
- Method of cultivation: 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)%. The synthetic sewage was prepared by dissolving glucose, peptone and monopotassium phosphate 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. This cultivation method was repeated once every day. The culturing was carried out at 25 ± 2 °C.
- Control: During the cultivation, appearance of the supernatant, precipitability, 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.

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

Biochemical oxygen demand (BOD)

Details on study design:

TEST CONDITIONS
- Test temperature: 25 ± 1 °C

TEST SYSTEM
- Culturing apparatus: 300 mL closed system
- Number of culture flasks/concentration: 2
- Absorbent for CO2: Soda lime No.1
- Stirring method: Test solution was stirred by a magnetic stirrer.

ANALYSIS OF TEST SOLUTION
- After the termination of cultivation, total organic carbon and the test substance in the test solutions were determined. The pH of the test solutions of (water + test substance) and (sludge + test substance) were measured.

Reference substance:

aniline

Key result

Parameter:

% degradation (O2 consumption)

Remarks:

BOD

Value:

1.8

Sampling time:

14 d

Details on results:

The percent biodegradation of the test item was calculated to be 1.8% based on the biochemical oxygen demand (BOD) at the end of the experment.

Results with reference substance:

The percent biodegradations of aniline calculated by BOD value were > 40% and > 60% at the 7th and 14th day, respectively.

Validity criteria fulfilled:

yes

Remarks:

When percentage biodegradations of aniline calculated by BOD value were beyond 40% and 60% at the 7th and 14th day, respectively , it was concluded that the test condition was valid.

Interpretation of results:

not readily biodegradable

Conclusions:

The test substance was not readily biodegradable under the conditions of the test.

Executive summary:

The ready biodegradability of the test item was investigated at a concentration of 100 mg/L using aerobic activated sludge incubated at 25 °C for 14 days under continuous stirring. The test was conducted equivalent or similar to OECD TG 301 C. It was not specified whether the study was compliant with GLP or not. The tested sludge was sampled from 10 different locations in Japan. The cultivated sludge that used in the test was exposed to 100 mg/L test substance or reference substance, aniline. In addition, a blank control was also involved in this test. After 2 weeks exposure, thepercent biodegradations of the reference substance were > 40% and > 60% at the 7th and 14th day, respectively. The percent biodegradation of the test item was calculate as 1.8% based on the biochemical oxygen demand (BOD) at the end of the experiment.Therefore, it was concluded that the test substance was not readily biodegradable under the conditions of the test.

Description of key information

The test substance was not readily biodegradable under the conditions of the test.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

The ready biodegradability of the test item was investigated at a concentration of 100 mg/L using aerobic activated sludge incubated at 25 °C for 14 days under continuous stirring. The test was conducted equivalent or similar to OECD TG 301 C. It was not specified whether the study was compliant with GLP or not. The tested sludge was sampled from 10 different locations in Japan. The cultivated sludge that used in the test was exposed to 100 mg/L test substance or reference substance, aniline. In addition, a blank control was also involved in this test. After 2 weeks exposure, the percent biodegradations of the reference substance were > 40% and > 60% at the 7th and 14th day, respectively. The percent biodegradation of the test item was calculate as 1.8% based on the biochemical oxygen demand (BOD) at the end of the experiment. Therefore, it was concluded that the test substance was not readily biodegradable under the conditions of the test.