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Toxicity to microorganisms

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Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1980
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Test procedure in accordance with generally accepted scientific standards and described in sufficient detail; there was no analytical confirmation of test substance concentrations in this study.
Principles of method if other than guideline:
The potential toxic action of water pollutants on water micro-organisms is performed with special reference to the toxicity for model organisms of biological self-purification by determining the toxicity thresholds to Pseudomonas putida (bacteria), Scendesmus quadricauda (green algae) and Entosiphon sulcatum (protozoa).
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
no
Details on sampling:
no data
Vehicle:
not specified
Details on test solutions:
Test solutions (diluted in sterile double-distilled water) are adjusted to pH 6.9 with hydrochloric acid or caustic potash. Two parallel dilution series are prepared in 300 ml Erlenmyer flasks. The dilutions contain 1 part v/v each of each pollutant solution in 2^0 to 2^14 parts v/v of mixture. Test solutions contain 8 ml of the pollutant dilution, 8 ml of double distilled water, 2 ml of the protozoan culture, and 2 ml of the inactivated bacterial culture (food source) for a total volume of 20 ml.
Test organisms (species):
Entosiphon sulcatum
Details on inoculum:
For maintenance of the test strain of Entosiphon sulcatum continuously innoculate the expected required number of stock cultures at 72 or 96-hour intervals. For this mix 8 ml of stock solution and 8 ml of sterile distilled water in 300-ml Erlenmyer flasks stoppered with metal caps and add 2 ml of a stock culture and 2 ml of adjusted bacterial suspension for Entosiphon stock cultures. Store stock cultures at 25 degrees C. Before innoculation control of the flasks containing the stock cultures nu means of an inverse microscope. Pretreatment of the bacteria used for feeding preliminary cultures of E. sulcatum does not differ from that of bacteria used for feeding the stock cultures. Keep preliminary cultures at 25 degrees C over 72 hours before using them for inoculation of the test cultures.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
No data
Hardness:
no data
Test temperature:
25 degrees C
pH:
Test solutions adjusted to pH 6.9.
Dissolved oxygen:
no data
Salinity:
not applicable
Nominal and measured concentrations:
not reported
Details on test conditions:
The test cultures are left for 72 hours at 25 degrees C.
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
other: Toxicity threshold
Effect conc.:
35 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks:
cell count
Details on results:
no data
Results with reference substance (positive control):
no data
Reported statistics and error estimates:
no data
Validity criteria fulfilled:
not applicable
Conclusions:
The toxicity threshold dose based on decreased cell counts of the protozoan, Entosiphon sulcatum, was 35 mg/L epichlorohydrin.
Executive summary:

The protozoan, Entosiphon sulcatum, was exposed to multiple nominal test concentrations of epichorohydrin at 25 degrees C for a period of 72 hours. Following the exposure period, cell counts of the protozoan were conducted in the control and epichlorohydrin test solutions. A toxicity threshold dose based on decreased cell counts of the protozoan, Entosiphon sulcatum, was determined to be 35 mg/L epichlorohydrin.

Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Test procedure in accordance with generally accepted scientific standards and described in sufficient detail, however there was no analytical confirmation of test solution concentrations in this study.
Principles of method if other than guideline:
The potential toxic action of water pollutants on water micro-organisms is performed with special reference to the toxicity for model organisms of biological self-purification by determining the toxicity thresholds to Pseudomonas putida (bacteria), Scendesmus quadricauda (green algae) and Entosiphon sulcatum (protozoa).
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
no
Details on sampling:
no data
Vehicle:
not specified
Details on test solutions:
Four parallel dilution series in 300 ml Erlenmyer flasks were performed in double-distilled water. Each of the dilutions contains 1 part v/v of the pollutant solution in 2^0 to 2^14 parts v/v of mixture.
Test organisms (species):
Pseudomonas putida
Details on inoculum:
Stock cultures of the test strain, P. putida, were kept in agar slant tubes incubatesd at 25 degrees C. New stock cultures were initiated at one week intervals. New inoculated stock cultures were incubated at 25 degrees C for 24 hours. If needed, preliminary cultures were prepared from stock cultures in nutrient medium agar in slant tubes (incubated at 25 degrees C for 24 hours). The cells were washed offo with sterile saline and the extinction of the monochromatic radiation was determined at 436 nm for a 10 mm layer of bacterial suspension. The final turbidity was adjusted to correspond to a standard suspension.
Test type:
static
Water media type:
saltwater
Limit test:
no
Total exposure duration:
16 h
Post exposure observation period:
After termination of the test period, the extinction of the monochromatic radiation at436 nm in a 10-mm layer in the inoculated dilution series was determined
Hardness:
no data
Test temperature:
25 degrees C
pH:
no data
Dissolved oxygen:
no data
Salinity:
Not applicable
Nominal and measured concentrations:
no data
Details on test conditions:
Control and dilution series were made up to a total volume of 100 ml in 300-ml Erlenmyer flasks stoppered with cotton lines plastic caps. Both the inoculated and non-inoculated dilution series were incubated at 25 degrees C for 16 hours.
Reference substance (positive control):
no
Duration:
16 h
Dose descriptor:
other: toxicity threshold
Effect conc.:
55 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Details on results:
no data
Results with reference substance (positive control):
no data
Reported statistics and error estimates:
no data
Conclusions:
The toxicity threshold dose based on growth inhibition of the bacteria, Pseudomonas putida, was 55 mg/L epichlorohydrin.

Description of key information

Based on a growth inhibition study with the protozoan, Entosiphon sulcatum, the 72-hour toxicity threshold for epichlorohydrin is 35 mg/L. 

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
35 mg/L

Additional information

Two microorganism studies were examined for epichlorohydrin and both were deemed reliable and useful for risk assessment. One study examined growth inhibition in the protozoan, Entosiphon sulcatum,over a 72 hour exposure period, while the other study measured growth inhibition of the bacteria, Pseudomonas putida,over a 16-hour exposure period. The growth inhibition test with E. sulcatum reported a toxicity threshold value of 35 mg/L epichlorohydrin. The growth inhibition study with P. putida reported a 16-hour toxicity threshold value of 55 mg/L epichlorohydrin. The value of 35 mg/L was selected as the key parameter for this endpoint, since this was the lowest toxicity value reported for microorganisms.