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Toxicity to soil microorganisms

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toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study is old, but well reported and used a rational methodology, e.g. counting colonies.

Data source

Reference Type:
study report

Materials and methods

Principles of method if other than guideline:
Effects of the test artcle on soil bacterial and fugal counts were determined after addition of the test article to a natural soil for 28 d. Effects were determined based on colony counts.
GLP compliance:
not specified

Test material

Constituent 1
Reference substance name:
14C-tetrabromophthalic anhydride
14C-tetrabromophthalic anhydride
Details on test material:
Prepared by Midwest Research Inst. Specific activity = 11.6 mCi/mM. Uniformly labeled in aromatic ring.

Sampling and analysis

Analytical monitoring:

Test substrate

Details on preparation and application of test substrate:
Acetone used to prepare a solution of the 14C-test article. A stock solution (10% acetone in water) then prepared for addition to soil.

Test organisms

Test organisms (inoculum):

Study design

Total exposure duration:
28 d
Soils were sampled at 0, 1, 2, 4, 7, 14 and 28 d for plating. Bacterial and fungal counts determined after 5 d.

Test conditions

Test temperature:
Soil: 28 degrees C at 70% humidity.
Plates: 28 degrees C.
70% of the 0.33 bar level or 14.31 g H2O/100 g dry soil.
Nominal and measured concentrations:
0, Vehicle control, 1, 10 ug/g dry soil

Results and discussion

Effect concentrations
Key result
Remarks on result:
other: Please see text below
Any other information on results.

Any other information on results incl. tables

Overall average bacterial and fungal counts were 6.9 x 10 +7 and 6.6 x 10 +4 / g dry soil, respectively, at the end of the incubation period. Bacterial counts increased during the first 14 d and declined slightly thereafter. The test article had a slight positive effect on the numbers of bacterial in soil which was statistically significant at the 10 µg/g level (p<0.001). Fungal population generally increased during the study, but the effect of treatment was not statistically significant.

Applicant's summary and conclusion

Validity criteria fulfilled:
PHT-4 did not adversely affect the number of bacterial or fungal colonies in soil over a 28-d exposure at concentrations up to 10 ug/g dry soil.
Executive summary:

PHT-4 did not adversely affect the number of bacterial or fungal colonies in soil over a 28-d exposure at concentrations up to 10 ug/g dry soil.