4,4'-methylenebis[N-sec-butylaniline]

Bioaccumulation: aquatic / sediment

Description of key information

A flow-through bioconcentration study was performed according to OECD Guideline 305 and GLP principles. The fish were exposed to a nominal concentration of 0.6 and 6.0 μg/L. The lower test concentration consisted entirely of [phenyl-U-14C]4,4'-methylenebis(N-sec-butyl)aniline. The higher test concentration consisted of 10% [phenyl-U-14C]4,4'- methylenebis(N-sec-butyl)aniline and 90% 4,4’-methylenebis- N-sec-butylaniline. Samples from the test medium were taken during the uptake phase on day -1 and 0 of the control, on day 1, 3, 7, 14, 21, and 28 of the control and both concentrations for LSC (total radioactivity) and HPLC-UV-RAD Analysis. During the depuration phase samples were taken, on day 29, 30, 31, 34, 35, 36, 37, 42, and 56 for the control and both concentrations for total radioactivity determination. Fish samples were taken on day  0, 1, 3, 7, 14, 21, and 28 of the uptake phase and day 30, 35, 42, and 56 of the depuration phase for LSC Analyses and HPLC-UV-RAD Analysis fish, and lipid content determination.

Based on the total radioactivity , the mean concentrations in the test medium, during the uptake phase were 0.51 ± 0.049 μg/L and 4.7 ± 0.50 μg/L at nominal concentrations of 0.6 and 6 μg/L, respectively. LC-UV-RAD analysis of the concentrated extracts showed that 86-100% of the measured radioactivity represented the parental compound, indicating that the test item was stable throughout the study.

At the nominal concentration of 0.6 μg/L, the average lipid normalised concentration in fish during the steady state was 2.5 ± 0.18 μg/g fish and the BCFssL was 4966 ± 238 L/kg. At the nominal concentration of 6 μg/L, the average normalised concentration in fish during the steady-state was 41 ± 8.9 μg/g fish and the BCFssL was 8820 ± 1800 L/kg.

Generally, the kinetic BCF values were relatively close to the steady-state BCF values, indicating that the overall study evaluation is robust despite some flaws in the employed models that could not be further identified and isolated. The BCFKLg (lipid-normalised growth corrected kinetic BCF) was 4214 and 9802 L/kg at the concentrations of 0.6 and 6.0 μg/L, respectively.

The t1/2g (growth-corrected half-life), was 6.9 and 8.9 days at the concentrations of 0.6 and 6.0 μg/L, respectively.

Based on the results collected in the present study, the test item is considered to be bioaccumulative in fish at a nominal exposure concentration of 0.6 μg/L and very bioaccumulative at a nominal exposure concentration of 6 μg/L when considering total radioactive residue concentrations. When considering parent related radioactive residue concentrations, uptake in fish tissue was still significant but formed on average about 40-50% of the total radioactive residue concentrations.