2,4-xylenol

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2000

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Remarks:

Gas chromatography (GC)

Details on test solutions:

Test solution volume: 100 mL OECD medium/container

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

No. of cells: 10E-4 cells/mL

Test type:

other: Static, shaking culture (100 rpm)

Water media type:

freshwater

Total exposure duration:

72 h

Test temperature:

23±2℃

Nominal and measured concentrations:

control, 2.00, 3.20, 5.00, 8.00, 13.0 and 20.0 mg/L
The results of a Gas chromatography (GC) analysis of the test solution, resulted in the ratio of the measured value at the start of exposure to the nominal value to be within ± 20%. Therefore, the test results were based on nominal concentrations.

Details on test conditions:

Illumination: Continuous illumination with bow 4000 lux (within ± 20% fluctuation, near flask liquid level)

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

9.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI not calculated

Remarks:

(recalculated value reported in the English summary version of the report, because endpoint values of 0-72 h were not reported)

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: (recalculated value reported in the English summary version of the report, because endpoint values of 0-72 h were not reported)

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

6.69 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

area under the growth curve (AUG)

Remarks on result:

other: 95% CI: 5.02-8.91 mg/L; 0-72 h value was reported from the original study report in Japanese

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

area under the growth curve (AUG)

Remarks on result:

other: 0-72 h value reported from the original study report in Japanese

Details on results:

The above EC50 and NOEC values for growth rate correpond to the recalcuated values for 0-72 h from the English summary, as the original values (see below) did not report endpoint values for 0-72 h.

Original values from the Japanese version of the study report.

1) Test substance concentration in test solution
 As a result of the analysis of the test solution, the ratio of the measured value at the start of exposure to the set value was within ± 20%.
Therefore, the set value was used to calculate the inhibition concentration

2) Inhibition concentration by comparison of the area under the growth curve
 50% growth inhibition concentration EbC50 (0-72) 2 : 6.69 mg / L (95% confidence interval: 5.02 to 8.91 mg / L)
Maximum ineffective concentration NOECb (0-72): 2.00 mg / L


3) Inhibition concentration by comparison of growth rate
 50% Growth Inhibition Concentration ErC50 (24-48): 14.0 mg / L (95% confidence interval: cannot be calculated)
 Maximum inactive concentration NOECr [24-48): 5.00 mg / L
 50% Growth Inhibition Concentration ErC50 (24-72): 13.2 mg / L (95% confidence interval: cannot be calculated)

Maximum inactive concentration NOECr (24-72): 5.00 mg / L

The following remark was mentioned in the English summary version of the study:

Tests conducted before FY 2002 needs confirmation of test results, because some of these tests were conducted using a dispersant.

Conclusions:

Under the study conditions, the 72 h ECr50 and NOEC values of the test substance based on effects on growth rate of aquatic algae were determined to be 9.7 and 1.8 mg/L, while the corresponing concentrations based on effects on biomass were determined to be 6.69 and 2 mg/L (nominal) respectively.

Executive summary:

A study was conducted to evaluate the toxicity of the test substance, to Pseudokirchneriella subcapitata (green algae) according to OECD Guideline 201, in compliance with GLP. The toxicity of the test substance to an exponentially growing culture of green algae was determined over an exposure period of 72 hours under static conditions with continuous shaking at 100 rpm. The test organisms were exposed to the test substance at nominal concentrations of 0, 2.00, 3.20, 5.00, 8.00, 13.0 and 20.0 mg/L. The results of a Gas chromatography (GC) analysis of the test solution, resulted in the ratio of the measured value at the start of exposure to the nominal value, to be within ± 20%. Therefore, the test results were based on nominal concentrations. Under the study conditions, the 72 h EC50 and NOEC values of the test substance based on effects on growth rate of the green algae were determined to be 9.7 and 1.8 mg/L (nominal) respectively, while the corresponding concentrations (EbC50 and NOEC) based on effects on biomass (represented in terms of area under the growth curve (AUG)) were determined to be 6.69 and 2 mg/L (nominal) respectively (MOEJ, 2001).

.

Reference 2

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2001

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Remarks:

HPLC (at the start and end of exposure)

Details on test solutions:

Test solution volume: 100mL (OECD medium)

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

No. of cells: 10E-4

Test type:

static

Water media type:

freshwater

Total exposure duration:

72 h

Test temperature:

23 ± 2℃

Nominal and measured concentrations:

Control; 1.75, 3.50, 7.00, 14.0, 28.0 and 56.0 mg/L (nominal concentrations)

Details on test conditions:

Lighting: 4000-50001ux (continuous lighting)

Reference substance (positive control):

not required

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

13 mg/L

Basis for effect:

growth rate

Remarks on result:

other: (recalculated value reported in the English summary version of the report, because endpoint values of 0-72 h were not reported)

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2.7 mg/L

Basis for effect:

growth rate

Remarks on result:

other: (recalculated value reported in the English summary version of the report, because endpoint values of 0-72 h were not reported)

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

7.47 mg/L

Basis for effect:

other: area under the growth curve (AUG)

Remarks on result:

other: 95% CI: 7.02-7.97 mg/L

Remarks:

(3.5 mg/L reported in the English summary)

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

3.5 mg/L

Basis for effect:

other: area under the growth curve (AUG)

Details on results:

The above EC50 and NOEC values for growth rate correpond to the recalcuated values for 0-72 h from the English summary, as the original values (see below) did not report endpoint values for 0-72 h.

Original values from the Japanese version of the study report.

1) Growth inhibition concentration by comparing the area under the growth curve
    EbC50 (0-72) = 7.47 mg/L (95% confidence interval: 7.02 mg/L to 7.95 mg/L)
    No-effect concentration (NOEC (area method 0-72)) = 3.50 mg/L

2) Growth inhibition concentration by comparison of growth rate
 ErC50 (24-48) = 15.3 mg/L (95% confidence interval: 14.2 mg/L to 16.6 mg/L)
 No-effect concentration (NOEC (velocity method 24-48)) = 7.00 mg / L
ErC50 (24-72) = 15.5 mg/L (95% confidence interval: 14.5 mg/L to 16.6 mg/L)
No-effect concentration (NOEC (velocity method 24-72)) = 7.00 mg/L
(The above concentrations are all based on the set concentration

Conclusions:

Under the study conditions, the 72 h ECr50 and NOEC values of the test substance based on effects on growth rate of aquatic algae were determined to be 13 and 2.7 mg/L, while the corresponing concentrations based on effects on biomass were determined to be 7.47 and 3.5 mg/L (nominal) respectively.

Executive summary:

A study was conducted to evaluate the toxicity of the test substance, to Pseudokirchneriella subcapitata (green algae) according to OECD Guideline 201, in compliance with GLP. The toxicity of the test substance to an exponentially growing culture of green algae was determined over an exposure period of 72 hours under static conditions with continuous shaking at 100 rpm. The test organisms were exposed to the test substance at nominal concentrations of 0, 1.75, 3.5, 7.0, 14.0, 28.0 and 56.0 mg/L.The test solutions were confirmed based on HPLC analysis. Under the study conditions, the 72 h EC50 and NOEC values of the test substance based on effects on growth rate of the green algae were determined to be 13 and 2.7 mg/L (nominal) respectively. The corresponding concentrations based on effects on biomass (represented in terms of area under the growth curve (AUG)) were determined to be 7.47 and 3.5 mg/L (nominal) respectively (MOEJ, 2000).

Description of key information

Based on the results from the available studies, the lower 72 h ErC50 and NOEC values of 9.7 and 1.8 mg/L (nominal) based on effects on growth rate has been considered further for hazard/risk assessment.

Key value for chemical safety assessment

EC50 for freshwater algae:

9.7 mg/L

EC10 or NOEC for freshwater algae:

1.8 mg/L

Additional information

Study 1: A study was conducted to evaluate the toxicity of the test substance, to Pseudokirchneriella subcapitata (green algae) according to OECD Guideline 201, in compliance with GLP. The toxicity of the test substance to an exponentially growing culture of green algae was determined over an exposure period of 72 hours under static conditions with continuous shaking at 100 rpm. The test organisms were exposed to the test substance at nominal concentrations of 0, 2.00, 3.20, 5.00, 8.00, 13.0 and 20.0 mg/L. The results of a Gas chromatography (GC) analysis of the test solution, resulted in the ratio of the measured value at the start of exposure to the nominal value, to be within ± 20%. Therefore, the test results were based on nominal concentrations. Under the study conditions, the 72 h EC50 and NOEC values of the test substance based on effects on growth rate of the green algae were determined to be 9.7 and 1.8 mg/L (nominal) respectively, while the corresponding concentrations (EbC50 and NOEC) based on effects on biomass (represented in terms of area under the growth curve (AUG)) were determined to be 6.69 and 2 mg/L (nominal) respectively (MOEJ, 2001).

Study 2: A study was conducted to evaluate the toxicity of the test substance, to Pseudokirchneriella subcapitata (green algae) according to OECD Guideline 201, in compliance with GLP. The toxicity of the test substance to an exponentially growing culture of green algae was determined over an exposure period of 72 hours under static conditions with continuous shaking at 100 rpm. The test organisms were exposed to the test substance at nominal concentrations of 0, 1.75, 3.5, 7.0, 14.0, 28.0 and 56.0 mg/L.The test solutions were confirmed based on HPLC analysis. Under the study conditions, the 72 h EC50 and NOEC values of the test substance based on effects on growth rate of the green algae were determined to be 13 and 2.7 mg/L (nominal) respectively. The corresponding concentrations based on effects on biomass (represented in terms of area under the growth curve (AUG)) were determined to be 7.47 and 3.5 mg/L (nominal) respectively (MOEJ, 2000).

Based on the results from the available studies, the lower 72 h ErC50 and NOEC values of 9.7 and 1.8 mg/L (nominal) based on effects on growth rate has been considered further for hazard/risk assessment.