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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Data is from peer reviewed journal
Qualifier:
according to guideline
Guideline:
other: refer below principle
Principles of method if other than guideline:
The toxic effect of substance 2, 3-dimethyl phenol in Photobacterium phosphoreum (strain: FEI 162095) was observed for 15 min.
GLP compliance:
no
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2,3-dimethylphenol
- Molecular formula (if other than submission substance): C8H10O
- Molecular weight (if other than submission substance): 122.16 g/mol
- Substance type: Organic
- Physical state: Solid
Analytical monitoring:
not specified
Vehicle:
not specified
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances):
- Method: laboratory prepared reagent (Finnish Environmental Institute); 15 deg C; 1253 luminometer
Test organisms (species):
Photobacterium phosphoreum
Details on inoculum:
- Strain: strain FEI 162095
- Laboratory culture: The freeze-dried Photobacterium phosphoreum bacteria were reconstituted by adding 12.5-ml 2% NaCl into the reagent bottle and incubating it at +4°C for 20 min before use.
Test type:
static
Water media type:
not specified
Total exposure duration:
15 min
Post exposure observation period:
No data
Hardness:
No data
Test temperature:
15 deg C
pH:
No data
Dissolved oxygen:
No data
Salinity:
No data
Nominal and measured concentrations:
No data
Details on test conditions:
No data
Reference substance (positive control):
not specified
Key result
Duration:
15 min
Dose descriptor:
EC50
Effect conc.:
28 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: 50 percent reduction in light
Details on results:
No data
Results with reference substance (positive control):
No data
Reported statistics and error estimates:
No data
Validity criteria fulfilled:
not specified
Conclusions:
The effect concentration i.e EC50 value of 2, 3-dimethyl phenol is considered to be 28 mg/l for micro organism species Photobacterium phosphoreum in 15 min.exposure period.
Executive summary:

Toxicity test was performed with Laboratory-prepared freeze-dried photobacterial reagent (Photobacterium phosphoreum strain FEI 162095) registered in the Finnish Environment Institute. The freeze-dried bacteria were reconstituted by adding 12.5-ml 2% NaCl into the reagent bottle and incubating it at +4°C for 20 min before use. The concentration of 2, 3-dimethyl phenol in the test (mg/L) which caused a 50% reduction in light after exposure of 2,3dimethyl phenol for 15 min. The EC50 value of 2, 3-dimethyl phenol is considered to be 28 mg/l for Photobacterium phosphoreum bacteria.

Description of key information

Toxicity test was performed with Laboratory-prepared freeze-dried photobacterial reagent (Photobacterium phosphoreum strain FEI 162095) registered in the Finnish Environment Institute. The freeze-dried bacteria were reconstituted by adding 12.5-ml 2% NaCl into the reagent bottle and incubating it at +4°C for 20 min before use. The concentration of 2, 3-dimethyl phenol in the test (mg/L) which caused a 50% reduction in light after exposure of 2,3dimethyl phenol for 15 min. The EC50 value of 2, 3-dimethyl phenol is considered to be 28 mg/l for Photobacterium phosphoreum bacteria.

Key value for chemical safety assessment

EC50 for microorganisms:
28 mg/L

Additional information

Four studies including experimental data from peer reviewed journals for micro organism toxicity endpoint of target chemical 2,3-dimethylphenol (Cas no. 526-75-0) were summarized as follows:

 First experimental study suggest toxicity test was performed by Kahru et. al (2000) with Laboratory-prepared freeze-dried photobacterial reagent (Photobacterium phosphoreum strain FEI 162095) registered in the Finnish Environment Institute. The freeze-dried bacteria were reconstituted by adding 12.5-ml 2% NaCl into the reagent bottle and incubating it at +4°C for 20 min before use. The concentration of 2, 3-dimethyl phenol in the test (mg/L) which caused a 50% reduction in light after exposure of 2,3dimethyl phenol for 15 min. The EC50 value of 2, 3-dimethyl phenol is considered to be 28 mg/l for Photobacterium phosphoreum bacteria.

Another experiment indicates Mirotox test was performed with Vibrio fischeri to find toxicity of 2, 3-dimethyl phenol. MicrotoxTM Reagent (Vibrio fischeri NRRL-B 11177). (AZUR Environmental, Carlsbad, California, USA). The freeze-dried reagent was reconstituted and bacteria cultivated, harvested, and frozen in cryoprotectant as described in paper (Kahru et al., 1996). The thawed bacterial suspension was used for the toxicity tests. The amount of viable bacteria in the case of all photo bacterial tests was ~10⁶ bacteria per ml test solution. The concentration of 2, 3-dimethyl phenol in the test (mg/L) which caused a 50% reduction in light after exposure of 2, 3-dimethyl phenol for 15 min. The EC50 value of 2, 3-dimethyl phenol is considered to be 5.3 mg/l in Vibrio fischeri NRRL-B 11177. (A. Kahru et al;Environ Toxicol 15: 431-442, 2000)

Same data source (i.e A. Kahru et al;Environ Toxicol 15: 431-442, 2000) also suggest Biotox test was performed with Vibrio fisheri to find toxicity of 2, 3-dimethyl phenol. Vibrio fisheri 1500 Reagent (Vibrio fischeri NRRL-B11177). from the BioTox test (Labsystems, Helsinki, Finland). The freeze-dried reagent was reconstituted with 12.5-ml 2% NaCl, incubated at +4°C for 20 min and, prior to the assay, further diluted five-fold with 2% NaCl. The concentration of 2, 3-dimethyl phenol in the test (mg/L) which caused a 50% reduction in light after exposure of 2, 3-dimethyl phenol for 15 min. The EC50 value of 2, 3-dimethyl phenol is considered to be 5.2 mg/l in Vibrio fischeri NRRL-B 11177.

And last study from another peer reviewed journal Water Pollution Research Journal Canada; Volume 26, No. 3, 361-431, 1991 indicate toxicity study of micro-organism to the test substance was conducted using Photobacterium phosphoreum, strain NRRL-B-11177 (also referred to as Vibrio fischerii, strain NRRL-B-11177).When test bacteria was exposed to the test substance 2,3-dimethylphenol with exposure duration of 5, 15 and 30 mins, reduction in light output was observed. Thus, based on reduction in light output by the test organism, the EC50 value during 30 mins exposure period was found to be 3.36 mg/l.

Thus all aquatic micro organism studies available for 15-30 min. exposure period indicate the effect concentration is in the range of 3.36 to 28 mg/l. And all EC50 values on the basis of reduction in light output effect. Based on the EC50 values it is concluded that target chemical 2,3-dimethylphenol (Cas no. 526-75-0) may have toxicity concern to micro organism for acute exposure period.