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EC number: 247-156-8
CAS number: 25640-78-2
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:
Toxicity values [mg/L]
LC50(96 h) >0.75
Ozburn et al. 1980
LC50(96 h) = 0.28
LC50(96 h) = 0.60
Spawn, hatch, fry
NOEC(21d) = 0.43
EC50(48 h) = 0.24
EC50(48 h) = 0.17
EC50(48 h) = 0.27
NOEC(21d) = 0.028
ErL50(72h) >100 NOELR = 100
Aniol et al. 2011
ErC50(72 h) = 0.15
NOEC(72 h) = 0.027
(1-methylethyl)-1,1'-biphenyl [CAS no. 25640-78-2]
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
Short-term toxicity to aquatic
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
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
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.
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