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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Four tests with three different pre-treatments were permformed:
1. Short pre-treatment: 7PPD showed 6.272 % respiration inhibition of activated sludge at the highest test item concentration of 100 mg/L with freshly prepared test solution. An EC10 of > 100 mg/L and an EC50 of >100 mg/l were obtained in this test. The effect value relates to nominal concentration, since no analytical monitoring was performed.
2. 17-hours-pretreatment: The test item showed 20.08 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/L with a 17 h pretreated test solution. An EC10 of 96.7 mg/L and an EC50 of >1000 mg/l were obtained in this test.
3. Five-day-pre-treatment:
a) High concentration test: The test item showed 27.2 % respiration inhibition of activated sludge at the highest test item concentration of 400 mg/L. An EC50 of >400 mg/l was obtained in this test.
b) Low-concentration test: The test item showed 0 % respiration inhibition of activated sludge at the highest test item concentration of 40 mg/L. An EC50 and EC10 of >40 mg/L, and a NOEC of >= 40 mg/L were obtained in this test.
Finally, no significant effects were seen in any of these studies. The stated key values for chemical safety assessment have to be read as >40 mg/L (EC10 and EC50), and >=40 mg/L (NOEC).

Key value for chemical safety assessment

EC50 for microorganisms:
40 mg/L
EC10 or NOEC for microorganisms:
40 mg/L

Additional information

1. Freshly prepared test solution:

In order to test the toxicity to microorganism of the substance, activated sludge from a domestic sewage plant was exposed to the test solution of 100 mg/L, blank control solution and solution with positive reference substance for a period of 3 hours.

The test item was added into Erlenmeyer flasks (incubation vessels) to about 130 mL deionised water and was stirred before testing (equilibration phase) for 1 hour.

Dissolved oxygen was recorded and respiration rates were claculated. No physico-chemical oxygen consumption was observed at the concentration of test substance. A respiration inhibition of 6.272 % was observed at 100 mg/L. An EC10 and an EC50 of > 100 mg/L were determined.

2. Test solution with 17 hours pre-treatment in water:

In order to test the toxicity to microorganism of the substance, activated sludge from a domestic sewage plant was exposed to the test solution of five nominal concentrations of the substance (10, 32, 100, 320 and 1000 mg/L), blank control solution and solution with positive reference substance for a period of 3 hours.

The test item was added into Erlenmeyer flasks (incubation vessels) to about 130 mL deionised water and was stirred before testing (equilibration phase) overnight for 16 hours.

Dissolved oxygen was recorded and respiration rates were claculated. No physico-chemical oxygen consumption was observed at the highest concentration of test substance. No respiration inhibition was observed at 100 mg/L; and 24.08 % inhibition at 1000 mg/L. An EC10 of 96.7 mg/L and an EC50 of > 1000 mg/L were determined.

3. Five day pre-treatment:

The test item was added into Erlenmeyer flasks (incubation vessels) to about 400 mL deionised water and was stirred before testing (equilibration phase) for 114 hours.

Currenta study 2014/0115/04:

In order to test the toxicity to microorganism of 7PPD after aging in water for a period of 5 days, activated sludge from a domestic sewage plant was exposed to the test solution of five nominal concentrations of the substance ( 25, 50, 100, 200 and 400 mg/L), blank control solution and solution with positive reference substance for a period of 3 hours.

The test item was added into Erlenmeyer flasks (incubation vessels) to about 130 mL deionised water and was stirred before testing (equilibration phase) for 115 hours.

Dissolved oxygen was recorded and respiration rates were claculated. The physico-chemical oxygen consumption has been determined at 400 mg/L test item concentration. As nearly no physico-chemical oxygen consumption was observed at that test item concentration this observation also holds true for the lower test item concentrations. 27.2 % respiration inhibition was observed at 400 mg/L.

As no clear NOEC could be derived from this study, another study (2014/0115/05) was performed covering the lower concentration level.

Currenta study 2014/0115/05:

To test the toxicity to microorganism of 7PPD after aging in water for a period of 5 days, activated sludge from predominantly domestic sewage plant was exposed to the test solution of five nominal concentrations of the substance ( 2.5, 5, 10, 20 and 40 mg/L), blank control solution and solution with positive reference substance for a period of 3 hours.

The present study has been performed additionally to Currenta study 2014/0115/04 where no definite NOECs could be achieved.

An EC50 and EC10 of >40 mg/L, and a NOEC of >= 40 mg/L were obtained.

The afore-mentioned toxicity studies are classified as acceptable and satisfy the guideline requirements for the toxicity study to microoragnisms.

Other studies:

Two studies performed with p-hydroquinone, a secondary hydrolysis product of 7PPD, show that this substance is relatively toxic to organisms (NOEC 1 mg/L, IC50 71 mg/L).