1-methylpiperazine

Endpoint summary

Additional information

Substance characterisation

1 -methylpiperazine is well-soluble in water (>200 g/L). It has a measured log Kow of -0.57 and a mean measured Kd for soil of 14.4 L/kg is read-across from piperazine. The observed sorption to soil is higher than expected based on the measured log Kow. It is expected that one nitrogen of piperazine which is protonated under environmental conditions (pKa = ±9.4) will sorb to the negatively charged surface of soil. This also explains the poor correlation with the organic matter content of the three soils tested. Based on these results, sorption to soil will be low and sorption to lipids will be negligible. Bioaccumulation is not expected to occur. A realistic worst-case BCF of 3.9 L/kg as observed for piperazine will be used in risk assessment for 1-methylpiperazine. With the low Henry's Law Constant of 0.334 Pa .m3/mol at 20°C the rate of volatilization from water is considered minimal.

Based on the available studies on biodegradation and the relatively low sorption potential, 1 -methylpiperazine is expected to be non-persistent in water, soil or sediment and for more than 99% removed from waste water in a sewage treatment plant.

The available biodegradation studies show fast degradation when adapted sludge or sessile microorganisms (which settled on glass beads during flow through of river water containing low µg/L test substance) are used

as inoculum in a closed bottle test. In these tests, the microorganisms in the closed bottle are capable of growing at high rates because N-methylpiperazine was degraded within a week.

Based on this high observed degradation rate it is very likely that in the number of competent microorganisms in the old OECD 302b studies and activated sludge used for the GLP test was not sufficient. This indicates that the competent micro-organisms are not wide dispersively available thus that 1 -methylpiperazine should be considered as inherently biodegradable.