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Ecotoxicological information

Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
guideline study conducted under GLP with chemical analysis. Raw data available.
Qualifier:
according to guideline
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
Analytical monitoring of test substance concentrations was performed at day 0 and after, 1, 11, 12, 20, and 21 d
- nominal concentrations: 0 (control), 0.0081, 0.016, 0.033, 0.065, and 0.13 mg/L
- mean measured concentrations: 0.0029, 0.0049, 0.014, 0.039, and 0.076 mg/L (time weighted average)
- Sampling method: the test solution was collected via a micropipette and immediately fixed with phosphate solution
- Sample storage conditions before analysis: the analysis sample were stored in a refrigerator at 4°C until the time of analysis
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution (100 mg/L) was prepared. The desired test concentrations were obtained by pipetting a fixed volume of the stock solution into the test vessels containing test medium.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): no vehicle used
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: waterflea (Daphnia magna)
- Strain/clone: not reported
- Source: formerly: National Institue for Environmental Studies, Environmental Agency; Currently: Independent Administrative Institution National Institute for Environmental Studies
- Age of parental stock (mean and range, SD): <=24 h
- Method of breeding: Parent daphnids were breed in Elendt M4 medium. The entire solution was replaced twice a week. 20 animals were held in 800 mL medium at 20 +/- 1°C with a photoperiod of 16 h light/8 h dark and a light intensity of 800-1200 lux. The daphnids were fed with Pseudokirchneriella subcapitata (0.1-0.2 mg C/d/parent daphnia) every day except for Saturdays and Sundays.
- Feeding during test: yes
- Food type: Pseudokirchneriella subcapitata
- Amount/Frequency: daily feeding at 0.1-0.2 mg C/d/parent daphnia) every day (animals were fed at 0.1 mg C/d until 4 d of age; 0.15 mg C/d for 5-10 d of age, and 0.2 mg C/d for 11 d of age and later)

ACCLIMATION: not necessary
- Acclimation conditions (same as test or not): yes
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Hardness:
230-240 mg/L as CaCO3
Test temperature:
20.2-20.7°C during the whole exposure period in all test solutions
pH:
7.8-8.3 during the whole exposure period in all test solutions
Dissolved oxygen:
8.1-8.9 mg/L (92.6-100.8% of the air saturation value) during the whole exposure period in all test solutions
Salinity:
no data
Nominal and measured concentrations:
nominal: 0 (control), 0.0081, 0.016, 0.033, 0.065, and 0.13 mg/L
mean measured (time weighted average): 0 (control), 0.0029, 0.0049, 0.014, 0.039, and 0.076 mg/L
During the 24 hour exposure periods a fast dissipation of hydroquinone was observed. Initial concnetrations of the test solutions were measured at day 0, 11 and 20 and the respective aged solutions at day 1, 12 and 21. At the beginning of the exposure periods the measured concentrations were between 68.8-78.5% of nominal on day 0, 64.2-90.0% on day 11 and 72.8-81.8% on day 20. During the 24 hour exposure period the hydroquinone concentrations decreased to <7.5% (
Details on test conditions:
TEST SYSTEM
- Test vessel: glass beaker
- Type (delete if not applicable): closed (a glass lid was placed on the top of the test vessel)
- Material, size, headspace, fill volume: glass/100 mL/20/80 mL
- Aeration: no aeration during the exposure period
- Type of flow-through (e.g. peristaltic or proportional diluter): testing conducted under semi-static conditions
- Renewal rate of test solution (frequency/flow rate): the test solution was replaced every 24 h
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Elendt M4 medium was used for the tests
- Culture medium different from test medium: no
- Intervals of water quality measurement: Temperature, pH, dissolved oxygen, and total hardness were measured 6 times (day 2, 3, 8, 9, 18, 19) during the exposure period in new and old solutions

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light/8 h dark
- Light intensity: 800-1200 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):
-Parent daphnias: Deaths, natation, appearance etc. were observed every day; daphnias survived until the end of exposure: body length
-Young animals: first day of birth; number of surviving young animals was recorded everyday starting from the first day of birth; number of dead animals, aborted eggs, occurrence of male individuals etc.

VEHICLE CONTROL PERFORMED: no vehicle used

RANGE-FINDING STUDY
- Test concentrations: 0.07, 0.11, 0.16, 0.24, 0.35 mg/L nominal
- Results used to determine the conditions for the definitive study: yes
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
0.006 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
0.054 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
other: body length of parent daphnids
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
0.003 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
> 0.076 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
other: first day of birth
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
0.039 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
other: body length of parent daphnids
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
0.005 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
0.076 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
other: first day of birth
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
0.076 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
other: body length of parent daphnias
Duration:
21 d
Dose descriptor:
LC50
Effect conc.:
0.061 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 95% c.i.: 0.027-0.81 mg/L
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
0.08 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks on result:
other: 95% c.i.: 0.058-0.12 mg/L
Results with reference substance (positive control):
48 h EC50=0.62 mg/L (Elendt M4 used as medium)
Reported statistics and error estimates:
The 21 d LC50 and the 95% c.i. were calculated using the Probit method ('EcoTox-Statics'). The 21 d EC50 and the 95% c.i. were calculated using the Logit method ('EcoTox-Statics'). NOEC and LOEC were calculated using the Bartlett method, ANOVA, the Dunett method, and the Kruskal-Wallis rank sum test ('EcoTox-Statics').

The long-term toxicity of hydroquinone was investigated in a study conducted according to OECD Guideline 211 (Daphnia magna Reproduction Test). The following results were obtained:

-number of deaths and death rate of parent daphnias:

a. the death rate of parent daphnias in the control at the end of exposure was 0%

b. the death rate of parent daphnias at the end of exposure in each test concentration was 0% at 0.0029 mg/L, 20% at 0.0049 mg/L, 0.014 mg/L, and 0.039 mg/L, and 70% at 0.076 mg/L

-average cumulative number of surviving offspring:

a. average cumulative number of surviving offspring per surviving parent daphnia in the control at the end of exposure was 95.5 +/- 4.4

b. average cumulative number of surviving offspring per surviving parent daphnia in each test concentration at the end of exposure

-0.0029 mg/L: 94.7 +/- 5.3

-0.0049 mg/L: 84.1 +/- 6.1

-0.014 mg/L: 80.1 +/- 9.0

-0.039 mg/L: 66.9 +/-11.0

-0.076 mg/L: 46.7 +/-9.0

-first day of birth

a. the first day of birth in the control ranged from 7 -10 d (average: 8.1 +/- 0.74 d)

b. the first day of birth in each test concentration

-0.0029 mg/L: 8.0 +/- 0

-0.0049 mg/L: 8.5 +/- 0.85

-0.014 mg/L: 8.4 +/- 0.97

-0.039 mg/L: 8.5 +/- 0.85

-0.076 mg/L: 8.7 +/- 1.89

-body length of the parent daphnias

a. control: 4.3 +/- 0.11

b. at test concentrations

-0.0029 mg/L: 4.2 +/- 0.07

-0.0049 mg/L: 4.2 +/- 0.06

-0.014 mg/L: 4.1 +/- 0.11

-0.039 mg/L: 4.2 +/- 0.13

-0.076 mg/L: 4.0 +/- 0.26

-occurrence of resting eggs, etc.

resting eggs or male individuals were not observed in any of the tests

The 21 d LC50 for parental daphnias was calculated to be 0.061 mg/L based on mean measured concentrations.

The calculated 21 d EC50, NOEC and LOEC for inhibition of reproduction were calculated to be 0.080, 0.0029, and 0.0049 mg/L based on mean measured concentrations. The nominal concentrations were 0 (control), 0.0081, 0.016, 0.033, 0.065, and 0.13 mg/L.

 Nominal conc. (mg/L) day 0 new   day 1 old  day 11 new  day 12 old  day 20 new  day 21 old  TWA conc. (mg/L)  Mean measured initial (mg/L)   
Control  <0.0012    <0.0036  <0.0012  <0.0012  <0.0012  <0.0012  <0.0012   <0.0012
0.0081  0.0059    <0.0012  0.0052  <0.0012  0.0059  <0.0012  0.0029   0.0057
0.016  0.011    <0.0012  0.013  <0.0036  0.012  <0.0012  0.0049   0.012
0.033  0.024    0.0049  0.030  0.015  0.027  <0.0036  0.014   0.027
0.065  0.051    0.022  0.059  0.033  0.052  0.025  0.039   0.054
0.130  0.099    0.051  0.120  0.054  0.100  0.053  0.076   0.106
 

However, hydroquinone is known to be fast degraded to several toxic degradation products depending on the environmental conditions like oxygen, pH and light (e.g. p-benzoquinone). The degradation products were not analyses in this study.

Provided that the formed degradation products are also of high ecotoxicity the evaluation of the test based on the concentration of the parent compound alone may overestimate its toxicity. Provided further that the total amount of toxic equivalents is stable during the exposure period the initial concentration is regarded as relevant concentration. Therefore, the daphnia test is re-evaluated based on the measured initial concentration. Thus, a 21 d NOEC=0.0057 mg/L based on recalculated measured initial concentration was found. The testing/validity criteria laid down in the OECD Guideline 211 are fulfilled (e.g. mortality of the parent animals at the end of the test: <20%; mean number of live offspring produced/parent animal surviving at the end of the test: >=60; test medium; feeding etc.).

Validity criteria fulfilled:
yes
Conclusions:
The long-term toxicity of hydroquinone was investigated in a study conducted according to OECD Guideline 211 (Daphnia magna Reproduction Test). A 21 d NOEC (reproduction)=0.0057 mg/L based on recalculated measured initial concentration was found.
Executive summary:

The long-term toxicity of hydroquinone was investigated in a study conducted according to OECD Guideline 211 (Daphnia magna Reproduction Test) under GLP. Daphnids were exposed to nominal concentrations of 0 (control), 0.0081, 0.016, 0.033, 0.065, and 0.13 mg/L under semi-static conditions with a 24 hour renewal period of the test water. The test concentrations were monitored via HPLC/UV in three exposure periods on days 0 -1, 10 -11 and 20 -21. The mean values of the measured initial concentrations were

0.0057. 0.012, 0.027, 0.054 and 0.106 mg/L. During the 24 hour test period the hydroquinone concentration decreased rapidly.

The authors used the mean measured concentrations for the evaluation. The mean measured concentrations (time-weighted average) were 0 (control), 0.0029, 0.0049, 0.014, 0.039, and 0.076 mg/L for 21 d. Effect parameters observed were inhibition of reproduction, cumulative number of surviving offspring, first day of birth, death and body length of parent daphnias, occurrence of aborted eggs and male individuals. The 21 d LC50 for parental daphnids was calculated to be 0.061 mg/L based on mean measured concentrations. The calculated 21 d EC50, NOEC and LOEC for inhibition of reproduction were calculated to be 0.080, 0.0029, and 0.0049 mg/L based on mean measured concentrations.

However, hydroquinone is known to be fast degraded to several toxic degradation products depending on the environmental conditions like oxygen, pH and light (e.g. p-benzoquinone). The degradation products were not analyses in this study.

Provided that the formed degradation products are also of high ecotoxicity the evaluation of the test based on the concentration of the parent compound alone may overestimate its toxicity. Provided further that the total amount of toxic equivalents is stable during the exposure period the initial concentration is regarded as relevant concentration. Therefore, the daphnia test was re-evaluated based on the measured initial concentration. Thus, a 21 d NOEC=0.0057 mg/L based on recalculated measured initial concentration was found. The testing/validity criteria laid down in the OECD guideline 211 are fulfilled.

This study is regarded as reliable without restriction.

Description of key information

The long-term toxicity of hydroquinone was investigated in a GLP-study conducted according to OECD Guideline 211 (Daphnia magna Reproduction Test). A 21 d NOEC (reproduction)=0.0057 mg/L based on recalculated measured initial concentration was found.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Dose descriptor:
NOEC
Effect concentration:
0.006 mg/L

Additional information

The long-term toxicity of hydroquinone was investigated in a study conducted according to OECD Guideline 211 (Daphnia magnaReproduction Test) under GLP. Daphnids were exposed to nominal concentrations of 0 (control), 0.0081, 0.016, 0.033, 0.065, and 0.13 mg/L under semi-static conditions with a 24 hour renewal period of the test water. The test concentrations were monitored via HPLC/UV in three exposure periods on days 0 -1, 10 -11 and 20 -21. The mean values of the measured initial concentrations were

0.0057. 0.012, 0.027, 0.054 and 0.106 mg/L. During the 24 hour test period the hydroquinone concentration decreased rapidly.

The authors used the mean measured concentrations for the evaluation. The mean measured concentrations (time-weighted average) were 0 (control), 0.0029, 0.0049, 0.014, 0.039, and 0.076 mg/L for 21 d. Effect parameters observed were inhibition of reproduction, cumulative number of surviving offspring, first day of birth, death and body length of parent daphnias, occurrence of aborted eggs and male individuals. The 21 d LC50 for parental daphnids was calculated to be 0.061 mg/L based on mean measured concentrations. The calculated 21 d EC50, NOEC and LOEC for inhibition of reproduction were calculated to be 0.080, 0.0029, and 0.0049 mg/L based on mean measured concentrations.

However, hydroquinone is known to be fast degraded to several toxic degradation products depending on the environmental conditions like oxygen, pH and light (e.g. p-benzoquinone). The degradation products were not analyses in this study.

Provided that the formed degradation products are also of high ecotoxicity the evaluation of the test based on the concentration of the parent compound alone may overestimate its toxicity. Provided further that the total amount of toxic equivalents is stable during the exposure period the initial concentration is regarded as relevant concentration. Therefore, the daphnia test was re-evaluated based on the measured initial concentration. Thus, a 21 d NOEC=0.0057 mg/L based on recalculated measured initial concentration was found.