Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability

Phototransformation in air

No data available (not required for REACH)

Hydrolysis

Due to its chemical structure, (1-methylethyl)-1,1'-biphenyl cannot be hydrolysed. The structure of the molecule does not contain any hydrolysable groups.

Phototransformation in water

No data available (not required for REACH)

Phototransformation in soil

No data available (not required for REACH)

Biodegradation

Biodegradation in water: screening tests

Results of biodegradation tests with (1-methylethyl)-1,1'-biphenyl are apparently inconsistent; however, two studies are considered to be invalid and, hence, have been disregarded. In one valid GLP-guideline study according to OECD TG 310 (Fiebig/Noack 2013), pass level for ultimate ready biodegradability (60% degradation based on CO2 production) was reached, but the 10-day window was not met, which in essence was 18 to 20 days. In the same test, primary biodegradation was 97 % already after 6 days.

In the second test, a pre-guideline study (Mendoza/DOW 1981) using a test substance concentration below water solubility (< 0.5 mg/L), complete

degradation based on O2 consumption within 10 days was reported . This study has to rejected, because the test concentrations applied were too low as to provide reliable and evaluable O2-consumption rates. In the third study according to OECD TG 301 C (Handley/ Safepharm 1994), no biodegradation was achieved. Due to solubility problems, the result of this study is assessed not to be representative of the biodegradation characteristics of isopropylbiphenyl, and therefore, is disregarded. (1-Methylethyl)-1,1'-biphenyl is graded as readily biodegradable but failing the 10-day window.

Biodegradation in water and sediment: simulation tests

No data available

Biodegradation in soil

No data available

Mode of degradation in actual use

No data available (not required for REACH)

Bioaccumulation

Bioaccumulation: aquatic / sediment

The bioaccumulation potential of (1-methylethyl)-1,1'-biphenyl was investigated in a pre-guideline study similar to OECD TG 305 E based on uptake and depuration rate constant (Ozburn et al 1980). BCF for low (3.5 µg/L) and high (24.1 µg/L) test substance concentrations were 2896 and 10790, respectively. Especially the second value seems extremely high for a substance with the structure of isopropylbiphenyl. Validity of measured values were assessed comparing them to BCF values of the supporting substance 4-ethylbiphenyl and to BCF estimates for isopropylbiphenyl using several calculation/QSAR methods. With the exception of one value (3471), all comparative values were below 2000. The BCF value of 10790 is considered to be not valid and is disregarded. As key value for (1-methylethyl)-1,1'-biphenyl, the BCF of 2896 is taken.

Bioaccumulation: terrestrial

No data available (not required for REACH)

Transport and distribution

Adsorption/Desorption

Koc value for (1-methylethyl)-1,1'-biphenyl was estimated using an accepted calculation method (program KOCWIN v2.00 included in US EPA EPI Suite 4.11). A Koc (estimate from MCI) of 25055 (log Koc 4.3989) was calculated (Wildschütte/MWC 2013) indicating distribution of (1-methylethyl)-1,1'-biphenyl predominately in soil and sediment.

Henry’s Law constant

Henry's Law constant for (1-methylethyl)-1,1'-biphenyl was determined using a batch air stripping method (Mendoza/DOW 1981). HLC values were measured for both, the 3- and 4-isopropybiphenyl isomers present in the test substance. Values were determined to be 173 and 238 Pa m³/mol, respectively, indicating only moderate evaporation from water.

Distribution Modelling

Results of distribution modelling with a Fugacity level III model (component of US EPA EPI Suite 4.11) give evidence that (1-methylethyl)-1,1'-biphenyl will be distributed mostly into soil (ca. 80%) and to a much lesser extent into sediment (ca. 11%) and water (ca. 8%). Percentage in air is minor (2.4%) (Wildschütte/MWC 2013).