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Description of key information

Short-term toxicity to fish

One study (Harlan 2010) with reliability 1 according to Klimisch was available and was selected as key study.

The summary of this key study is the following:

In a 96 -hour acute toxicity study (Harlan, 2010),Brachydanio reriowere exposed to 4 -tert-butylpyrocatechol (4 -TBC) under semi-static conditions according to the Commission Regulation (EC) n° 440/2008, Part C.1 and the OECD Guideline for Testing of Chemicals, n°203 (1992).

Zebra fish were exposed to control and test item at nominal concentration of0.10,0.21,0.44,0.91, 1.91 and 4 .0 mg/L.

In the analyzed test medium samples from the start of the test medium renewal periods, the measured test item concentrations ranged between 83 and 113% of the nominal values. During the test medium renewal periods of 24 hours, a decrease of the test item concentration in the test media was determined. At the end of the test medium renewal periods, 38 to 102% of the nominal values were found.

The biological results were based on mean measured concentrations calculated as time-weighted means of the test item concentrations measured at the start of the test medium renewals and the concentrations measured in the samples at the end of the renewal periods.

 

Nominal test item
concentration (mg/L)

Mean measured test item concentration

(mg/L)

0.10

0.065

0.21

0.16

0.44

0.37

0.91

0.85

1.91

1.95

4.0

4.3

The test fish were observed for mortality and visible abnormalities after approximately 3, 24, 48, 72 and 96 hours test duration.

 

In the control and at the mean measured test concentrations up to and including 0.065 mg/L, all fish survived until the end of the test and no visible abnormalities were observed in the test fish. At the next higher mean measured test concentration of 0.16 mg/L, all test fish showed one or several visible abnormalities and six fish died at this test concentration after 96 hours of test duration. At the two next higher mean measured test concentrations of 0.37and 0.85 mg/L, all test fish died after 48 hours test duration. At the two highest mean measured test concentrations of 1.95 and 4.3 mg/L, all fish were dead already after 24 hours of test duration.

Thus, the 96‑hour NOEC and LC0of 4 -TBC to zebra fish were both determined to be 0.065 mg/L. The 96‑hour LOEC was 0.16 mg/L.

The96‑hour LC50of 4 -TBC was calculated to be0.12 mg/Lwith a 95% confidence interval of 0.075 to 0.18 mg/L. The 96‑hour LC100was 0.37 mg/L.

In summary, the biological test results were as follows:

- 96-hour LC50:

0.12mg/L (95% CL: 0.075 –0.18mg/L)

- 96-hour NOEC and LC0:

0.065 mg/L

- 96-hour LC100:

0.37mg/L

- 96-hour LOEC:

0.16mg/L

 

 

Based on the results, 4 -TBC was very toxic for Zebra fish.

This study is classified as acceptable and satisfies the guideline requirements for acute fish toxicity study.

Short-term toxicity to aquatic invertebrates:

Two studies were available. One was selected as key study (Harlan 2010) with reliability 1 according to Klimisch, and the other one (CRIT 1995) was quoted reliability 3 due to the lack of chemical analysis of the test item.

The summary of the key study is the following:

In a 48 -hour acute toxicity study (Harlan, 2010),Daphnia magnawere exposed to 4 -tert-butylpyrocatechol (4 -TBC) under semi-static conditions according to the Commission Regulation (EC) n° 440/2008, Part C.2 and the OECD Guideline for Testing of Chemicals, n°202 (2004).

Daphnids were exposed to control and test item at nominal concentration of0.22,0.46, 1.0, 2.2, 4.6 and 10 mg/L.

In the analyzed test medium samples from the start of the test medium renewal periods, the measured test item concentrations ranged between 98 and 106% of the nominal values. During the test medium renewal periods of 24 hours, a decrease of the test item concentration in the test media was determined. At the end of the test medium renewal periods, 61 to 94% of the nominal values were found.

The biological results were based on mean measured concentrations calculated as geometric means of all measurements:

Nominal test item
concentration (mg/L)

Mean measured test item concentration

(mg/L)

% of nominal

0.22

0.18

79.7

0.46

0.41

88.3

1.0

0.94

93.8

2.2

1.97

89.7

4.6

4.47

97.1

10

9.94

99.4

 

Mortality / immobilization were observed daily.

After 48 hours of exposure, no immobilized test organisms were determined in the control. At the concentrations of0.18to 0.94 mg/L, the immobilization was between 30 and 50%. From the concentration of 1.97 mg/L onwards, all daphnids were found to be immobile. Except immobility, no other adverse effects were observed in the test concentrations at observation after 48 hours.

The48 -hour EC50was0.48mg/Lwith 95% confidence limits of0.10and 1.1 mg/L.

The 48 -hour NOEC was <0.18mg/L, since a statistically significant effect was observed at this test concentration.

In summary, the biological test results were as follows (based on measured concentrations):

- 24-hour EC50:

0.94 mg/L (95% CL.: 0.63 – 1.3 mg/L)

- 48-hour EC50:

0.48mg/L (95% CL.:0.10– 1.1 mg/L)

- 48-hour NOEC:

<0.18mg/L

- 48-hour EC100:

1.97 mg/L

 

Based on the results, 4 -TBC was very toxic for aquatic invertebrates.

This study is classified as acceptable and satisfies the guideline requirements for acute daphnids toxicity study.

Long-term toxicity to aquatic invertebrates:

One study (Wildlife 2013) with reliability 1 according to Klimisch was available and was selected as key study.

The summary of this key study is the following:

The objective of the study (2013) was to determine the effects of 4 -tert-butylpyrocatechol (4 -TBC) on the survival, growth and reproduction of the cladoceran,Daphnia magna, during a 21 -day exposure period under flow-through test conditions.

The study was performed according to the OECD 211 guideline and under GLP conditions.

 

Daphnids were exposed to a geometric series of five test concentrations and a negative control (dilution water). Two replicate test chambers were tested for each treatment and control group. Each replicate contained two compartments with five daphnids, resulting in a total of 20 daphnidsin each treatment and control group. The nominal test concentrations were 10, 26, 64, 160 and 400 µg/L. Mean measured test concentrations were determined from samples of test water collected from each treatment and control group at test initiation, at approximately weekly intervals during the test and at test termination.

As the measured concentrations deviated more than 20 per cent from the nominal in some cases, biological results are based on the mean measured concentrations. The corresponding mean measured concentrations were: 6.3, 19, 56, 135 and 359 µg/L.

 

Parent animals were observed daily during the test for mortality, the onset of reproduction, and clinical signs of toxicity. Following the onset of reproduction, the numbers of offspring were counted three times per week, and at test termination (Day 21). Body lengths and dry weights of the surviving parent animals were measured at the end of the exposure period. Observations of the effects of 4-TBC on survival, reproduction and growth were used to determine the no-observed-effect concentration (NOEC), the lowest-observed-effect concentration (LOEC). EC50and EC10values were determined based on reproduction and on parent animals immobility at test termination.

 

There were no significant treatment-related effects on survival or growth at concentrations ≤ 359 µg/L. Reproduction, expressed as the total number of live neonates produced per parent animal present at test initiation or as number of live neonates produced per reproductive day, was the most sensitive biological endpoint measured in this study. Daphnids exposed to 4-TBC at concentrations ≥ 359 µg/L had statistically significant reductions in reproduction in comparison to the negative control. Consequently, the NOEC, based on reproduction, was 135 µg/L and the LOEC was 359 µg/L.

 

The 21-day EC50values for immobility of parent animals and for reproduction were both greater than 359 µg/L, the highest concentration tested. The 21-day EC10value for immobility of parent animals also was greater than 359 µg/L. The 21-day EC10value, based onthe mean number oflive neonates per adult present at test initiation, was 207 µg/L, with the 95% confidence interval of 4.4 to 296 µg/L. The 21-day EC10value, based onthemean number of live young per reproductive day, was 169 µg/L with the 95% confidence interval of -47.8 to 281 µg/L.

 

The biological results were summarized as follows (based on measured concentrations):

- 21-day EC50, Immobility:

 > 359 µg/L

 - 21-day EC50, Reproduction:

 > 359 µg/L

 - 21-day NOEC, Reproduction:

 135 µg/L

 - 21-day LOEC, Reproduction:

 359 µg/L

 

Based on the results, 4 -TBC was toxic to daphnids with long lasting effects.

This study is classified acceptable and satisfies the guideline requirements for chronic daphnids toxicity study.

Toxicity to algae:

One study (Harlan 2010) with reliability 1 according to Klimisch was available and was selected as key study.

The summary of this key study is the following:

The influence of 4 -tert-butylpyrocatechol (4 -TBC) on the growth of the freshwater green algal speciesPseudokirchneriella subcapitatawas investigated in a 72 -hour static test (Harlan, 2010) according to the Commission Regulation (EC) n° 440/2008, Part C.3 and the OECD Guideline for Testing of Chemicals, n°201 (2006).

The nominal concentrations of the test item of0.25,0.55,1.20,2.55,5.55and 12 mg/L were tested in parallel with a control.

The measured concentrations of 4 -TBC in the test media of the nominal test concentrations of0.25to 12 mg/L were between 91 and 100% of the nominal values at the start of the test and 64 and 81% of the nominal values at the end of the test. During the test period of 72 hours, a decrease of test item concentration in the test media occurred.

The biological results were to related to the mean measured test item concentrations (calculated as the geometric means of the concentrations measured at the start and the end of the test):

 

Nominal test item concentration

Mean measured concentration of the test item
(geometric mean)

[mg/L]

[mg/L]

[% of nominal]

0.25

0.20

78

0.55

0.46

84

1.20

0.99

83

2.55

2.10

82

5.55

4.73

85

12.0

10.8

90

 

Additionally, the media of the nominal concentrations of0.55and5.55mg/L were incubated over the test duration under the same test conditions as well as in the dark but without algae. The mean measured concentrations (calculated as geometric means) of these test item samples were in the range of 83 to 92% of nominal. The comparison between light and dark incubation did not result in a distinct difference in the concentrations (see table below).

 

Nominal test item concentration

Measured test item concentration

algae + illuminated

illuminated

dark

[mg/L]

[mg/L]

[% of nominal]

[mg/L]

[% of nominal]

[mg/L]

[% of nominal]

0.55

0.460

84

0.455

83

0.509

92

5.55

4.73

85

4.95

89

4.76

86

 

The test item had a statistically significant inhibitory effect on growth of the algae (average growth rate and biomass) after the test period of 72 hours at the mean measured concentration of0.46mg/L and at all higher test concentrations (results of Williams t-tests, one-sided, alpha = 0.05).

Thus, this concentration was determined to be the 72 -hour LOEC.

The 72 -hour NOEC was determined to be0.20mg/L, since up to and including this mean measured test concentration, the growth and biomass of the algae after 72 hours were not statistically significantly lower than in the control.

The biological results were summarized as follows:

Parameter

Growthrate

Biomass

(0-72 h)

EC10  (mg/L)

2.29

1.37

95% confidenceinterval

1.96 – 2.60

1.07– 1.62

EC20  (mg/L)

3.82

1.83

95% confidence interval

3.45– 4.16

1.52– 2.09

EC50  (mg/L)

10.17

3.18

95% confidence interval

9.44– 11.07

2.87 – 3.53

NOEC (mg/L)

0.20

0.20

LOEC (mg/L)

0.46

0.46

 

Based on the results, 4 -TBC was harmful for algae.

This study is classified as acceptable and satisfies the guideline requirements for acute algae toxicity study.

 

Toxicity to microorganisms:

One study (Harlan 2010) with reliability 1 according to Klimisch was available and was selected as key study.

The summary of this key study is the following:

In a study (Harlan, 2009), the inhibitory effect of the substance 4-tert-butylpyrocatechol on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated in a 3-hour respiration inhibition test according to OECD guideline for Testing of Chemicals, n°209 (1984).

The nominal concentrations tested were 10, 32, 100, 320 and 1000 mg/L.

In addition, two controls and three different concentrations of the reference item 3,5-dichlorophenol (5, 16 and 50 mg/L) were tested in parallel. The results of these reference treatments (EC50= 11 mg/L within the guideline-recommended range of 5 - 30 mg/L) confirmed suitability of the activated sludge.

EC50= 16 mg/L(95% C.L.: 3.5 - 32 mg/L)

NOEC = 0.6 mg/L(95% C.L.: 0.0 - 3.0 mg/L)

Based on the results of this study, 4 -tert-butylpyrocatechol would be considered as harmful for microorganisms.

This study is classified as acceptable and satisfies the guideline requirements for toxicity study to activated sludge in a respiration inhibition test.

Additional information