Registration Dossier

Administrative data

Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-guideline study but conducted under sound scientific principles

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1986
Report Date:
1986

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
A radiorespirometric method was used to determine the compatibility of the test substance with secondary waste treatment microorganisms . The
procedure used microorganisms from a laboratory-maintained activated sludge unit. These microorganisms were exposed to [14C] glucose and
the test substance. The extent of conversion of the [14C] glucose to [14C] carbon dioxide in the presence of the test article was compared to
glucose conversion without test article.
GLP compliance:
not specified
Remarks:
pre-GLP

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 1,3-Diisopropylbenzene
- Analytical purity: 95.2%
- Impurities (identity and concentrations):
- Purity test date: 10/15/1985
- Lot/batch No.: X- 17111-47A

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
The intial concentrations of the stock solutions of the test substance was determined. Radioactivity was measured after the 5 hour exposure by liquid scintillation spectrometer.

Test solutions

Vehicle:
no
Details on test solutions:
Preparation of Stock Test Substance Solutions:
The stock test solutions were prepared in distilled water as follows: 100 mg of the test article was mixed with 1000 mL of distilled water by mechanical stirring for 24 hours at 22°C. The mixture was centrifuged at 10,000xG for 10 minutes . After centrifugation, the top several mLs of liquid was discarded and the remainder saved for use as the stock test article solution. The pH was not measured and no pH adjustment was made. This stock solution subsequently was diluted by a factor of four in the test vessels to achieve the final nominal test article concentrations of (1/4)C, were C
denotes the concentration of the test substance in the stock solution .

Test organisms

Test organisms (species):
activated sludge
Details on inoculum:
Microorganisms were cultured in sludge tanks containing two chambers: a 300 mL aeration/mixing chamber and a 75 mL clarifying chamber. The
contents of the sludge tanks were mixed and aerated by water-saturated air which entered at the bottom of the aeration/mixing chamber. The
microorganisms were maintained on a glucose-peptone- nutrient mixture. This solution vas pumped dropvise into the sludge tank aeration/mixing chamber. The sludge unit had a retention time of 6 hours . Cellular debris, waste products, and excess fluid were drained off at the overflow sidearm located on the settling chamber. Two sludge units were used. Air and nutrients were introduced simultaneously into both sludge tanks . The sludge units were seeded periodically with microorganisms obtained from an industrial waste treatment plant. Seeding occurred once per week, with about 10% of each unit being replaced with new mixed liquor suspended solids (MLSS).

Selection of Microorganisms for Testing:
Between 350 and 400 mL of mixed liquor from the laboratorymaintained domestic activated sludge units were centrifuged in tared 50 mL plastic centrifuge tubes at 7000xG for 5- 15 minutes at 4°C. The supernatant liquid was decanted and the precipitate was washed in 300 mL of oxygenated 0.02M potassium phosphate buffer, pH 6.9. The tube contents were then centrifuged as before, the supernatant liquid was decanted, and the tube and contents were weighed. The contents of the tube were resuspended in sufficient oxygenated potassium phosphate buffer to give a final activated sludge concentration of 10-20 mg/mL .

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
5 h

Test conditions

Test temperature:
27C

Results and discussion

Effect concentrations
Duration:
5 h
Dose descriptor:
NOEC
Effect conc.:
>= 0.22 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
other: inhibition of conversion of radiolabeled glucose

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
Exposure to 0. 22 mg/L of 1,3-Diisopropylbenzene, the highest concentration tested, had no observed inhibitory effects on the microorganisms, that is above the water solubility limit.
Executive summary:

A radiorespirometric method was used to determine the compatibility of 1,3-Diisopropylbenzene with secondary waste treatment microorganisms. The procedure used microorganisms from a laboratory-maintained activated sludge unit. These microorganisms were exposed to (14C) glucose and 1,3-Diisopropylbenzene. The extent of conversion of the (14C) glucose to (14C) carbon dioxide in the presence of the test article was compared to glucose conversion without test article. Exposure to 0. 22 mg/L of 1,3-Diisopropylbenzene, the highest concentration tested, had no observed inhibitory effects on the microorganisms, that is above the water solubility limit.