Hydrocarbons, C9, aromatics

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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study done according to OECD Guideline 209.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

yes

Remarks:

Due to the high vapor pressure of the test substance, the substance would have been lost to volatilization during the standard 3 hr exposure. Instead the test substance was injected directly into the oxygen uptake for an exposure duration of 10 min.

GLP compliance:

yes (incl. QA statement)

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

90% domestic sewage from Chester Sewage Works (Welsh Water) collected on day of the test. The mixed liquor suspended solids content was 3.64 g dry solids/l.

Test type:

static

Limit test:

yes

Total exposure duration:

10 min

Test temperature:

20 +/- 0.6°C

pH:

7.5-7.7

Nominal and measured concentrations:

Nominal: 1.1, 3.3, 9.9, 33, 99 mg/l

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

10 min

Dose descriptor:

NOEC

Effect conc.:

> 99 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

10 min

Dose descriptor:

EC50

Effect conc.:

> 99 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

- Effect concentrations exceeding solubility of substance in test medium: yes

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: 3-hr EC50 = 14 mg/l

Concentration	Respiration Rate (mg O2/g dry solids/h)	Inhibition %
Control	17.8	0
1.1	18.8	0
3.3	18.6	0
9.9	18.6	0
33	18.0	0
99	18.0	0

Validity criteria fulfilled:

yes

Conclusions:

Hydrocarbons,C9, Aromatics is not expected to be toxic to aerobic sewage treatment. The NOEC is > 99 mg/l (nominal). The EC50 is also > 99 mg/l (nominal).

Executive summary:

This study was done to determine if Shellsol A had an inhibitory effect on the respiration rate of activated sludge. Activated sludge was exposed to 1.1, 3.3, 9.9, 33, or 99 mg/l of test substance. The exposure duration, 10 min, was much less than the normal duration of 3 hrs. However, due to the high volatility of the substance, it would be rapidly lost to volitization during the vigorous aeration of the activated sludge process. The test substance showed no inhibition of respiration as compared to negative controls. The positive control substance inhibited respiration up to 93.2%. Therefore, the results of the study are considered valid, and the substance is not expected to be toxic to aerobic sewage treatment, and the NOEC and EC50 are both > 99 mg/l (nominal).

Description of key information

There is data available for this substance.Key data is summarized below.

 

Hydrocarbons,C9, Aromatics is not expected to be toxic to aerobic sewage treatment. The NOEC is >99 mg/L (nominal). The EC50 is also > 99 mg/L (nominal).