2-Propenoic acid, 2-methyl-, monoester with 1,2-propanediol, reaction products with dipropylene glycol and 1,1'-methylenebis[isocyanatobenzene]

Bioaccumulation: aquatic / sediment

Description of key information

The bioaccumulation potential is expected to be low.

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.

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 adsorb 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 homologues were to be present in natural waters, their uptake by organisms is considered unlikely. The smallest homologue HPMA-MDI-HPMA (n=0) has a molecular weight of 538.60 g/mol. For the larger homologues (n≥1) molecular weights are above 900 g/mol. All homologues have log Kow values above 5 (KOWWIN v1.68). These constituents are therefore unlikely to cross biological membranes. According to Lipinski’s “rule of 5”, developed to identify drug candidates with poor oral absorption, a molecular weight > 500 g/mol and a log Kow > 5 indicate a low potential of absorption after oral uptake (Lipinski, 1997). Furthermore, a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test (OECD 422) conducted with UMA 121 did not reveal any test substance-related effect (Takawale, 2013). As stated in the “Guidance on information requirements and chemical safety assessment Chapter R.11: PBT Assessment”, the complete absence of effects in mammalian long-term studies is an indication that the compound is either chronically non-toxic and/or that it is not taken up to a significant extent.

Finally, as UMA 121 is poorly soluble and consists of an unknown amount of different homologues (n = 0, 1, 2, 3, etc.) it would be problematic to obtain meaningful results from a standard bioaccumulation study, due to analytical difficulties.

In conclusion, the exposure of aquatic organisms to UMA 121 is expected to be minimal, due to the low solubility of the UMA homologues. In the unlikely event of exposure, uptake of UMA 121 by organisms is considered unlikely, based on the high molecular weight of the UMA homologues. The HPMA constituent, which might be released, is expected to have low bioaccumulation potential, due to its low log Kow value. Based on the available information, UMA 121 can be assumed to have low bioaccumulation potential.

References:

Lipinski CA, Lombardo F, Dominy BW, and Feeney PJ. 1997. Experimental and computational approaches to estimate solubility and permeability in drug discovery and development settings. Adv.Drug Deliv.Rev. 23: 3-25