Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

UMA 121 is the reaction product of the following substances:

- Methylendiphenyldiisocyanate, isomer mixture of 4,4’- and 4,2’-MDI (MDI) CAS No. 26447-40-5

- Dipropylene glycol (DPG) CAS No. 25265-71-8

- 2-hydroxypropylmethacrylate (HPMA) CAS No. 27813-02-1

The reaction product is a solid resin containing the polymer HPMA-MDI-(DPG-MDI)n-HPMA as homologues of n = 0, 1, 2, 3, etc. (no upper limit defined) as well as free HPMA.

The water solubility of UMA 121 was determined to be 0.4 mg/L in an OECD 105 study. However, taking into account that the water solubility is 130 g/L for HPMA (ECHA website, Registered substances) and 0.0002 - 0.002 mg/L for the shortest UMA homologue (n=0) (WSKOW v1.42 and WATERNT v1.01), it can be assumed that the 0.4 mg/L solubility is mainly due to HPMA and that the dissolution of UMA homologues is negligible. Additionally, it should be noted that the test substance was pestled to a powder for the purpose of the water solubility study. The resulting solubility value thus represents an absolute worst case compared to the water solubility of the substance in its normal resin form.

Release of UMA 121 to surface waters is unlikely, as it will be removed in sewage treatment plants to a high extent. As stated in the “Guidance on information requirements and chemical safety assessment Chapter R.7b: Endpoint specific guidance”, insoluble chemicals will be removed in the primary settling tank or fat trap of sewage treatment plants (ECHA, 2012). Possible remaining amounts would be adsorbed to the activated sludge. However, as discussed above HPMA is far more soluble than the rest of the constituents. It might thus dissolve into the water phase, but due to its ready biodegradability it would most likely be removed though biodegradation by the activated sludge (ECHA website, Registered substances).

If UMA 121 were to be released into the aquatic environment, HPMA might dissolve into the aqueous phase. As HPMA is readily biodegradable and has a low log Kow value of 0.72 (KOWWIN v1.68), rapid removal from the aquatic environment is also assumed in natural waters. The UMA homologues (n = 0, 1, 2, 3, etc.) are poorly soluble in water and have high log Kow (> 5; KOWWIN v1.68) and log Koc values (> 5; KOCWIN v2.00). Apart from a possible release of HPMA, UMA 121 is thus expected to remain stable and inert in the aqueous environment. Abiotic or biotic degradation is very unlikely under environmental conditions.

Also in the terrestrial environment UMA 121 will presumably remain stable and inert. Small amounts of HPMA may dissolve into the pore water, but will probably be rapidly biodegraded by soil microorganisms.

In conclusion, UMA 121 is expected to remain stable and inert if released into the environment. HPMA may be released from UMA 121 in small amounts, which will be rapidly removed via biodegradation.