Registration Dossier

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

For a summary on available key information, please see below.

Additional information

Because of the short carbon chain length of MPMD, any surface-active properties can safely be excluded. Due to the high primary and secondary pKa-values, MPMD will be present in the aqueous environment exclusively as a di-cation. This results firstly in a negligible volatility from water; and secondly, partitioning between n-octanol and water is exclusively into the water phase, leading to a very low Kow (log Kow <1) and excluding any partitioning based bioaccumulation. At the same time, two positive charges separated by only a short C5-spacer implies a very low (if any - for details see read-across report in IUCLID section 13) potential to cross biological membranes. Accordingly, there is no potential for bioaccumulation, and thus secondary poisoning is no issue for MPMD. Aliphatic amines are readily protonated at environmental pH and due to their positive charge are prone to bind to negatively charged solid matter. According to the available adsorption-desorption study (OECD 106; RL1) on read across source substance 1,6-hexane diamine (HMD), there is relevant binding to soil and sediment. In spite of this adsorptive behaviour, MPMD was shown to be readily biodegradable fulfilling the 10-day window requirement with total nitrification within 28 days (measured nitrate concentration approximately equalled the theoretical one). From these properties, rapid degradation in sewage treatment plants or the environment is expected which would lead to overall low environmental concentrations. In addition, due to adsorption on suspended matter or soil, bioavailable concentrations in the aquatic phase are expected to be low. Due to the observed rapid mineralization, accumulation in soil or sediment is not anticipated. This is confirmed by the study on nitrogen-transformation of read-across source substance HMD by soil organisms (OECD 216; RL 1): independently from the substance concentration (between 62.5 and 1000 mg/kg soil dry weight), consistently between 50% and 64% of the substance borne nitrogen was transformed to nitrate within 28 days, in addition to the nitrate stemming from amending soil with Lucerne meal containing nitrogen. As cleavage of the C-N-bonds is a prerequisite for nitrification and will reduce adsorption and increase bioavailability; and considering in addition ready biodegradability; this allows for concluding on rapid mineralization of MPMD within natural soil.