Reaction mass of (2R*,4R*,4aR*,9bS*)-2,4-dimethyl-4,4a,5,9b-tetrahydroindeno[1,2-d][1,3]dioxine and (2R*,4R*,4aS*,9bR*)-2,4-dimethyl-4,4a,5,9b-tetrahydroindeno[1,2-d][1,3]dioxine

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

A study on the microbial toxicity of the substance is not available. The ECHA guidance R.7b says that under certain conditions, the findings of the toxicity control in a study on the ready biodegradability can be used to derive a NOEC value for microbial activity. In the available, reliable study on ready biodegradability, no inhibition of microbiologic activity was seen in the toxicity control. The results of this toxicity are used to define the NOEC value and this approach is considered as reliable with restrictions.

Reason / purpose for cross-reference:

reference to other study

Principles of method if other than guideline:

The toxicity of the substance to microbial activity was tested in the context of a ready biodegradability study in accordance with OECD 301D. The substance and a positive reference substance were added to a testing flask together with inoculum from a municipal sewage treatment plant. The biodegradation of the positive reference substance over the period of the degradability study was monitored.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source of inoculum/activated sludge: Municipal sewage treatment plant, Hildesheim, Germany
- Laboratory culture: no
- Pretreatment: Activated sludge was filtered with folded filter. The first 200 mL of the filtrate were not used. The second filtrate effluent from the domestic waste water is used to initiate inoculation.
- Initial cell/biomass concentration: 10E+4 - 10E+6 Colony Forming Units (CFU)/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

14 d

Test temperature:

19-21 °C

pH:

7.2 -7.6

Dissolved oxygen:

The dissolved oxygen concentration was greater 6 mg/L over the period of 14 days

Nominal and measured concentrations:

1.5 mg/L test item
5.0 mg/L sodium acetate (positive reference item)

Details on test conditions:

Ten bottles containing the test substance, positive reference substance and inoculum were tested (Toxicity control)

Reference substance (positive control):

no

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

1.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

A degradation of 31% was observed after 14 days, which is above the threshold value of 25% given in the OECD TG.

Validity criteria fulfilled:

yes

Conclusions:

The substance is not inhibitory to the microbial activity of activated sludge at a nominal concentration of 1.5 mg/L.

Executive summary:

The microbial activity of the test substance was studied in the context of a ready biodegradability test according to OECD 301D by conducting a toxicity control. Test vessels containing 1.5 mg/L test substance, 5.0 mg/L sodium acetate (positive reference control) and the inoculum (acitivated sludge from a municipal sewage treatment plant processing domestic sewage) were incubated under aerobic conditions in the dark at 20 °C for a period of 28 days. The degradation of the test and reference substance was monitored by determining the dissolved oxygen concentration regularly. A degradation of 31% was observed after a period of 14 days. The threshold limit value of 25% after 14 days hence was exceeded and the substance did not significantly inhibit the microbial activity. A NOEC value of 1.5 mg/L for microbial activity can be derived from this study.

Description of key information

Experimental data on the toxicity of the test substance to microorganisms are not available. The toxicity control in the ready biodegradability study (OECD 301D) did not inhibit the activity of the inoculum at a concentration of 1.5 mg/L. 

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1.5 mg/L

Additional information

The microbial activity of the test substance was studied in the context of a ready biodegradability test according to OECD 301D by conducting a toxicity control. Test vessels containing 1.5 mg/L test substance, 5.0 mg/L sodium acetate (positive reference control) and the inoculum (acitivated sludge from a municipal sewage treatment plant processing domestic sewage) were incubated under aerobic conditions in the dark at 20 °C for a period of 28 days. The degradation of the test and reference substance was monitored by determining the dissolved oxygen concentration regularly. A degradation of 31% was observed after a period of 14 days. The threshold limit value of 25% after 14 days hence was exceeded and the substance did not significantly inhibit the microbial activity. A NOEC value of 1.5 mg/L for microbial activity can be derived from this study.