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Administrative data

Endpoint:
toxicity to microorganisms, other
Remarks:
determination of the inhibitory effect of water constituents on bacteria by Pseudomonas cell multiplication inhibition test
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study is in accordance with guidelines and is thought to be in accordance with GLP, however there is no evidence to support this.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1990

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest)
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
4-chloro-o-cresol
EC Number:
216-381-3
EC Name:
4-chloro-o-cresol
Cas Number:
1570-64-5
Molecular formula:
C7H7ClO
IUPAC Name:
4-chloro-2-methylphenol

Test organisms

Test organisms (species):
Pseudomonas putida

Study design

Test type:
not specified
Water media type:
not specified
Total exposure duration:
17 h

Test conditions

pH:
The pH range was 7.0 - 7.2 at 0h, not inoculated.
The pH range was 7.1 -7.2 at 17 h not inoculated.
The pH range was 5.1 - 6.8 at 17 h inoculated for concentrations up to 156.26 mg/L, at concentration above this (312.5 - 5000m g/L) the pH range was 7.0 - 7.1.

Results and discussion

Effect concentrationsopen allclose all
Duration:
17 h
Dose descriptor:
EC10
Effect conc.:
ca. 37 mg/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
other: optical density
Duration:
17 h
Dose descriptor:
EC50
Effect conc.:
ca. 110 mg/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
other: optical density
Duration:
17 h
Dose descriptor:
other: EC90
Effect conc.:
ca. 150 mg/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
other: optical density

Any other information on results incl. tables

The optical density at 436nm was measured after 17 hours. The results are summarised in the table below.

Concentration, mg/L Extinction Values
1 2 3 4 5
C 0.611 0.637 0.639 0.643 0
15.53 0.579 0.589 0.599 0.612 0.001
39.06 0.559 0.55 0.577 0.578 0
78.13 0.491 0.489 0.515 0.501 0.001
156.25 0.016 0.01 0.012 0.016 0.0001
312.5 0.003 0.003 0.003 0.002 0.001
625 0.004 0.004 0.004 0.004 0.003
1250 0.009 0.009 0.008 0.008 0.006
2500 0.016 0.017 0.017 0.016 0.013
5000 0.046 0.048 0.046 0.046 0.038
625 n 0.003 0.003 0.004 0.002 0.001
5000 n 0.045 0.052 0.049 0.05 0.047

C = control

1 - 4 = parallel tests, inoculated

5 = parallel test, not inoculated

Applicant's summary and conclusion

Conclusions:
EC50 110mg/L
Executive summary:

A guideline study was performed to measure the effect on bacterial growth of 4-chloro-o-cresol. The study was performed using Pseudomonas putida (DSM 50026) and the effect determined by measuring the optical density at 436nm. Concentrations of 4-chloro-o-cresol in the range 15.53 - 5000mg/L were used.

The results showed at test concentration 15.53 mg/L, the optical density was 93.9 % of the control, at 39.06 mg/L the optical density was 89.5% of control, at 78.13 mg/L, 78.7% of the control, at 156.25 mg/L, 2.0%, 312.5mg/L 0.3%, 625mg/L 0.2%, 1250mg/L 0.4%, 2500mg/L 0.6% and 5000mg/L 1.3% of the control.

The results indicate that at doses above 156.25 mg/L 4-chloro-o-cresol is cytotoxic. Two additional tests were performed whereby the 4 -chloro-o-cresol was neutralised, doses of 625mg/L and 5000mg/L both showed growth of 0.3% of the control, indicating that the neutralised substance is also cytotoxic at these levels.

The EC 50 derived from the results is 110mg/L.

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