1,2,4-trimethylbenzene

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP; non-guideline; experimental study; predates implementation of GLP and/or development of study guidelines but otherwise acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Ability of activated sludge microorganisms to oxidise aromatic organic compounds

Author:

Marion CV, Melaney GW

Year:

1964

Bibliographic source:

Proc 18th ind waste conf, eng ull, purdue univ, eng ext ser, 1964, pp297-308

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Warburg respirometer technique

GLP compliance:

no

Remarks:

Predates GLP

Test material

Test material information

Constituent 1

Reference substance name:

1,2,4-trimethylbenzene

EC Number:

202-436-9

EC Name:

1,2,4-trimethylbenzene

Cas Number:

95-63-6

Molecular formula:

C9H12

IUPAC Name:

1,2,4-trimethylbenzene

Details on test material:

No details

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Vehicle:

not specified

Details on test solutions:

500mg/l based on final vol 20ml

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludges from (1) municipal plant at Columbus, Ohio; (2) municipal plant at Hilliard, Ohio; (3) the plant serving Brookside Estates, nr. Linworth, Ohio. Suspended solids concentration was adjusted to 2,500 mg/l by removal of supernatant liquid or addition of tapwater. Sludge was not washed. No mineral salts added.

Study design

Test type:

other:

Water media type:

freshwater

Total exposure duration:

24 h

Post exposure observation period:

No data

Test conditions

Hardness:

No data

Test temperature:

20⁰C

pH:

No data

Dissolved oxygen:

No data

Salinity:

No data

Details on test conditions:

Sludge was blended for 10sec then pipetted into 125ml Warburg flasks containing test substrate. The flasks were shaken for 5-7 days at 20⁰C (waterbath). All members of a chemical family of compounds were run with the same adjusted sludge sample. Endogenous respiration of the sludge was measured in each experiment. Air oxidation or volatility of the substrate in the concentration used in the experiment were determined and corrections made when necessary. Results plotted as accumulative mg oxygen taken up by 1L of mixture. Control = oxygen uptake due to exogenous respiration.

Reference substance (positive control):

not specified

Results and discussion

Effect concentrations

Duration:

3 h

Dose descriptor:

other: Comparison with endogenous oxygen consumption. Classified as toxic since oxygen consumption lower than endogenous oxygen consumption.

Effect conc.:

500 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

During the first 3 hours 1,2,4-trimethylbenzene was toxic to all three sludges to different extends, based on inhibition of oxygen uptake compared to the control (endogenous respiration rate). Brookside was the most effected, followed by Hillard, with Columbus activated sludge being only minimally effected.

Any other information on results incl. tables

During the first 3 hours 1,2,4-trimethylbenzene was toxic to all three sludges to different extends, based on inhibition of oxygen uptake compared to the control (endogenous respiration rate). Brookside was the most effected, followed by Hillard, with Columbus activated sludge being only minimally effected. Inhibition (toxicity) was indicated by a negative oxygen uptake. In longer aeration periods, 5-7.5 days, 1,2,4-trimethylbenzene was significantly biodegraded (oxygen uptake about 2000 mg/L). Of all the polymethylated benzenes, 1,2,4-trimethylbenzene is the only one to be significantly biologically oxidized and is more susceptible to oxidation than o-xylene.

Applicant's summary and conclusion

Conclusions:

1,2,4-trimethylbenzene was found to be toxic to the three types of activated sludges to different extends. This endpoint indicates that 1,2,4-trimethylbenzene may be considered to be P (persistent) in the assessment of PBT, but will have no influence on the classification and labelling of this substance.

Executive summary:

This robust summary has a reliability rating of 2, because it is a non-GLP; non-guideline study, experimental study and predates implementation of GLP and/or development of study guidelines however, the procedure and means of analysis suggest that the methodology was appropriate to evaluate the required endpoint. There is otherwise no information in the article to suggest that the data are invalid. However, because the study did not follow recommended guidelines the interpretation of the results cannot be fully assessed against the guideline criteria and therefore the result is only an indication of inhibition.