1,2-dichlorobenzene

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge nitrification inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Basic data given (comparable to guidelines/standards)

Qualifier:

equivalent or similar to guideline

Guideline:

ISO 9509 (Toxicity test for assessing the inhibition of nitrification of activated sludge microorganisms)

GLP compliance:

not specified

Analytical monitoring:

yes

Vehicle:

not specified

Test organisms (species):

Nitrosomonas sp.

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Remarks on exposure duration:

no data

Details on test conditions:

Type: other: Inhibition of N-oxidation

Duration:

24 h

Dose descriptor:

IC50

Effect conc.:

47 mg/L

Nominal / measured:

not specified

Conc. based on:

not specified

Basis for effect:

other: Ammonia use

Conclusions:

The inhibition of nitrification of Nitrosomonas bacteria exposed to 1,2 -dichlorobenzene was investigated using a method similar to ISO DIS 9509. The IC50 (24 h) amounted to 47 mg/L.

Executive summary:

Blum & Speece (1991).

The inhibition of nitrification of Nitrosomonas bacteria exposed to 1,2 -dichlorobenzene was investigated using a method similar to ISO DIS 9509. The IC50 (24 h) amounted to 47 mg/L.

Description of key information

The inhibition of nitrification of Nitrosomonas bacteria exposed to 1,2-dichlorobenzene was investigated by Blum and Speece (1991) using a method similar to ISO DIS 9509. The IC50 (24 h) was reported as 47 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

47 mg/L

Additional information

The inhibition of nitrification of Nitrosomonas bacteria exposed to 1,2-dichlorobenzene was investigated by Blum and Speece (1991) using a method similar to ISO DIS 9509. The IC50 (24 h) was reported as 47 mg/L.

A number of additional studies (Boyles (1980), McFeters et al (1983), Ribo and Kaiser (1983))) reported lower concentrations but these are not considered as reliable as they were conducted using unsuitable test systems for the assessment of microorganisms in sewage treatment plants e.g. test organisms were marine species. Furthermore, tests with Pseudomonas putida (Bringnamm and Kuehn (1976, 1977, 1980)) are recommended to be used only in cases where no other test results are available.

Therefore the 24 h IC50 of 47 mg/L, reported by Blum and Speece (1991), has been selected as the key value for toxicity of microorganisms to 1,2 dichlorobenzene.