Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

To assess the aquatic toxicity of (1-methylethyl)-1,1'-biphenyl (isopropylbiphenyl, MIPB), data resulting from the supporting substance 4-ethyl-1,1'-biphenyl (4-EB) have been used in addition to test results obtained with isopropylbiphenyl. Utilisation of 4-ethylbiphenyl data is based on following reasons. Both substances, isopropylbiphenyl and 4-ethylbiphenyl, are closely related. Main molecular structure is the same (aromatic biphenyl-ring system substituted by a short chain alkyl group). They differ only in the alkyl-side chain by one methyl group which is absent in ethylbiphenyl. Physicochemical parameters are estimated to be very similar as well as behaviour in the environment. Metabolism is expected to follow the same principles (primary biotransformation in the alkyl-side chain eventually followed by hydroxylation of the biphenyl-ring system). According to their properties, toxicity of the two substances will be very similar. On these grounds, data obtained with ethylbiphenyl will also be used for characterisation of (1-methylethyl)-1,1'-biphenyl.

Toxicity data, acute and chronic, that have been located, are displayed in the following table:

Test Organism

Test Method

Toxicity values [mg/L]

Reliability

Source

Fish 

adult

OECD 203

LC50(96 h) >0.75

MIPB

Ozburn et al. 1980

fry

US-EPA 1975.

LC50(96 h) = 0.28

MIPB

Ozburn et al. 1980

adult

OECD 203

LC50(96 h) = 0.60

4-EB

NITE 1999

Spawn, hatch, fry

US-EPA1975

NOEC(21d) = 0.43

MIPB

Ozburn et al. 1980

Daphnia 

 

OECD 202

EC50(48 h) = 0.24

MIPB

 Muckle 2012

 

OECD 202

EC50(48 h) = 0.17

MIPB

Mendoza 1981

 

OECD 202

EC50(48 h) = 0.27

4-EB

NITE 1999

 

OECD 211

NOEC(21d) = 0.028

4-EB

NITE 1999

Alga 

 

OECD 201

ErL50(72h) >100 NOELR = 100

MIPB

Aniol et al. 2011

 

OECD 201

ErC50(72 h) = 0.15

NOEC(72 h) = 0.027

4-EB

NITE 2011

MIPB = (1-methylethyl)-1,1'-biphenyl [CAS no. 25640-78-2]

4-EB = 4-Ethylbiphenyl [CAS no. 5707-44-8]

Short-term toxicity to fish

For assessment of the short-term toxicity of (1-methylethyl)-1,1'-biphenyl to fish, one study for each, MIPB and 4-EB, is available (Ozburn et al. 1980 and CHRIP/NITE 1999). The study of Ozburn does not follow OECD/EU guidelines. In two 96h-flow-through tests, toxicity of MIPB to adult fish and to fry of flagfish was examined resulting in LC50 values of >0.75 and 0.28 mg/L, respectively. The study of CHRIP/NITE follows OECD TG 203. The 96h-LC50 with ricefish was 0.6 mg/L.

The 96h-LC50 values for adult fish of both studies fall in the same range. The lower value of 0.6 mg/L (CHRIP/NITE) for the supporting substance 4-ethylbiphenyl is used in the further assessment of (1-methylethyl)-1,1'-biphenyl.

Long-term toxicity to fish

In an early long-term toxicity study using flagfish, the endpoints of spawning impairment, hatching impairment (exposure period for each 21 d) and toxicity to fry (exposure period 10 d) were examined (Ozburn et al 1980). Thresholds (not further specified) determined were >0.42, >0.47 and 0.43 mg/L, respectively. The lowest distinct value (0.43 mg/L) is taken as key value for long-term toxicity to fish. But it is pointed out, that the LC50 established in a 96 h/4 d test with flagfish fry (0.28 mg/L) is lower than the threshold for the 10 d exposure test (0.43 mg/L). As there are other aquatic long term toxicity data available that are lower, this discrepancy is not further valued.

Short-term toxicity to aquatic invertebrates

For assessment of the short-term toxicity of (1-methyethyl)-1,1'-biphenyl to aquatic invertebrates, two studies are available (Muckle/LAUS 2012 and Mendoza/DOW 1981). One of them (Muckle/LAUS) was performed according to OECD TG 202 under GLP conditions. Results of both studies fall in the same range. 48h-EC50 was 0.24 and 0.167 mg/L respectively. For the supporting substance 4-ethylbiphenyl, a 48 h EC50 of 0.27 mg/L was determined in a test according to OECD TG 202 (CHRIP/NITE 1999). This is in good agreement with the results for MIPB.

The value of 0.24 mg/L of the Muckle/LAUS study is used as key value in the further assessment of (1-methylethyl)-1,1'-biphenyl as this is the lower of the two results from the guideline studies.

Long-term toxicity to aquatic invertebrates

Results are only available from a study with the supporting substance 4-ethylbiphenyl (CHRIP/NITE 1999). In this test according to OECD TG 211, the 21 d NOEC and the 21 d EC50 were determined to be 0.028 mg/L and 0.082 mg/L, respectively.

Toxicity to aquatic algae and cyanobacteria

Aquatic toxicity to algae and cyanobacteria was investigated in two studies according to OECD TG 201 using (1-methylethyl)-1,1'-biphenyl (Aniol/STZ 2011) and 4-ethylbiphenyl (CHRIP/NITE 1999) as test substance. The study of Aniol/STZ is a limit test. A water accommodated fraction with a nominal load of 100 mg/L was applied. Concentrations of dissolved test material could not be verified. No inhibition of algal growth was observed with this test setup (72 h EL50 >100 mg/L, 72 h NOELR 100 mg/L).

The CHRIP/NITE study with 4-EB was a standard test using graduate test concentrations. The test resulted in a 72 h EC50 of 0.15 mg/L and a 72 h NOEC of 0.027 mg/L. These values are taken as key values for further consideration.

Toxicity to microorganisms

For assessment of the toxicity to microorganisms, results of a ready biodegradation study with (1-methylethyl)-1,1'-biphenyl are use. In the toxicity controls of the test, no inhibition of microbial activity was observed at a MIPB concentration of 19.65 mg/L. This value is taken as NOEC in assessing the toxicity of (1-methylethyl)-1,1'-biphenyl to STP microorganisms.