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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
other: OECD 301C, MITI I Test
GLP compliance:
not specified
Specific details on test material used for the study:
not specified
Details on test solutions:
TEST CONDITIONS
- Composition of medium: 3 mL each of four stock solutions, as described in JIS K 0102-1986-21, are diluted to 1000 mL with purified water
- pH: 7.0
- pH adjusted: yes
- Suspended solids concentration: determined according to Method Japanese Industrial Standards (JIS) K 0102-1986-14.1
- Cultivation temperature: 25 °C
Test organisms (species):
activated sludge
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): In March, June, September, and December, sludge was sampled at the following 10 places in Japan: 1. Fukogawa city sewage plant, 2. Fukashiba industry sewage plant, 3. Nakahama city sewage plant, 4. Ochiai city sewage plant, 5. Kitakami river, 6. Shinano river, 7. Yoshino river, 8. Lake Biwa, 9. Hiroshima bay, 10. Dookai bay; sampling: 1. City sewage: Returned sludge from sewage plants was taken. 2. Rivers, lake and sea: Surface water and surface soil which were in contact with atmosphere were collected.
- Method of cultivation: About 30 minutes after ceasing aeration to the sludge mixture, supernatant corresponding to about 1/3 of the whole volume was removed. Then the equal volume of dechlorinated water was added to the remaining portion and aerated again, followed by addition of synthetic sewage at a concentration of 0.1% (w/v). This procedure was repeated once every day. The culturing was carried out at 25 ± 2 °C. 5 L of the filtrate of the supernatant of old activated sludge was mixed with 500 mL of the filtrate of the supernatant of new sludge and cultured at pH 7.0 ± 1.0 under sufficient aeration using prefiltered open air. 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.
- Concentration of sludge: 30 mg/L
Test type:
static
Water media type:
freshwater
Total exposure duration:
14 d
Test temperature:
The culturing was carried out at 25 ± 2 °C. 5
pH:
- pH: 7.0
Details on test conditions:
Standard test conditions of the modified MITI (I) test
Duration:
14 d
Dose descriptor:
other: no inhibition of biodegradation (94 % in 14 d)
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: biodegradation
Details on results:
After 14 d incubation the test material was biodegraded by 94 %.
There was no inhibiotion of biodegradation by the test material at 100 mg/L.
Percentage biodegradation(%) average
BOD = 94.3
TOC = 99
GC = 99
UV = 99
Conclusions:
In a standard modified MITI (I) test after 14 d incubation the test material was biodegraded by 94 %.
There was no inhibition of biodegradation by the test material at 100 mg/L.
Methyl methacrylate is not toxic to microorganisms.
Executive summary:

In a standard modified MITI (I) test after 14 d incubation the test material was biodegraded by 94 %.

There was no inhibition of biodegradation by the test material at 100 mg/L.

Methyl methacrylate is not toxic to microorganisms.

Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriate concentrations.

NOEC for microorganisms is considered to be >100 mg/l

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

Methyl methacrylate was non-toxic to activated sludge in a test for ready biodegradability according to the modified MITI (I) protocol. 94 % biodegradation were achieved within 14 d, indicating the absence of toxicity up to 100 mg/L. This is consistent with other microbial toxicity test results and with test data in higher aquatic organisms.