Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability

The phototransformation in air of 2,4,6-triisopropyl-m-phenylene diisocyanate was predicted with the help of the computer program AOPWIN v1.92 (EPIWIN software) by US-EPA , resulting in an atmospheric half-life of 0.280 days (around 3.40 hours) (Chemservice S.A., 2011).

Concerning hydrolysis, HYDROWIN v2.00 (EPIWIN software) by US-EPA detected ISOCYANATES as hydrolysable substance class (Chemservice S.A., 2012). The hydrolysis half-life will be less than 10 minutes at 25 °C and even at low pHs.

Biodegradation

Regarding biodegradation in water, one experimental result as well as two QSAR predictions are available for 2,4,6-triisopropyl-m-phenylene diisocyanate. The substance was not found as bacteriotoxic and no degradation had been occurred after 28 days (Müller, 1997). This result is supported by the prediction of BIOWIN v4.10 (EPIWIN software), which concludes that the substance is not readily biodegradable (Chemservice S.A., 2011). The START plug-in in Toxtree (v.2.1.0) assigns the chemical as "class III - unknown" (Chemservice S.A., 2011).

Regarding biodegradation in soil, Martens (1981) reported about the possibilities of the liberation of toxic aromatic amines under different conditions of disposal. It can be assumed that the polyether based polyurethane foams are largely resistant to microbial as well as chemical attack under all practical conditions of disposal. As overall result, no indication of any degradation of the isocyanate based polyureas was found.

Bioaccumulation

No experimental results are available for 2,4,6-triisopropyl-m-phenylene diisocyanate. The aquatic bioconcentration factor (BCF) was determined by the computer program BCFBAFWIN v3.00 (EPIWIN software) by US-EPA (Chemservice S.A., 2011). The potential to accumulate in organisms cannot be completely excluded, since the regression-based estimate results in a BCF of 7065 L/kg wet-wt and the Arnot-Gobas method in a value of 5970 L/kg wet-wt. A terrestrial bioaccumulation study is not triggered for a registration of a tonnage band of 100 - 1000 tons/year according to REACH Regulation (EC) 1907/2006.

Transport and distribution

Regarding the soil adsorption potential for 2,4,6-triisopropyl-m-phenylene diisocyanate only a QSAR prediction is reported which was performed by the computer program KOCWIN v2.00 (Chemservice S.A., 2011). A Koc value of 539300 L/kg (5.393 E+005 L/kg) was estimated by the Salbjic molecular connectivity (MCI) method, which is taken more seriously into account, due to the fact that it includes improved correction factors. The traditional method gives a value of 3639000 L/kg (3.639 E+006 L/kg).

Henry´s law states that the solubility of a gas in a liquid solution at a constant temperature will be proportional to the partial pressure of the gas which is above the solution (Henry, 1803). This information is not mandatory for a registration under REACH Regulation (EC) 1907/2006 in a tonnage band of 100 - 1000 tons/year. However, the Henry´s Law Constant can be predicted with the help of HENRYWIN v3.20 (Chemservice S.A., 2011). A constant of 7.49 Pa*m³/mol was predicted at 25 °C for the substance 2,4,6-triisopropyl-m-phenylene diisocyanate.

Monitoring data

Monitoring data are only available for the read across substance toluene diisocyanate. Atmospheric emissions are low, typical emission losses for TDI are 25 g/t (Tury, 2004). Laboratory studies show that the substance does not react with water in the gas phase at a significant rate. The primary degradation reaction of these aromatic diisocyanates in the atmosphere is expected to be oxidized by OH radicals with an estimated half-life of one day. Laboratory studies also show that this reaction is not expected to result in increased ground-level ozone accumulation. It is indicated that degradation by photolytically generated radicals, rather than by direct photolysis will occur. In a vapour phase no hydrolysis was detected. The reaction rate of TDI with OH radicals, measured relative to that of toluene, was estimated as >= 7.4 x 10E12 cm³/molecule/ sec. Both isomers of TDI were found to inhibit ozone formation and radical levels in all experiments. This atmospheric degradation of TDI by OH radicals raises concerns that the process might lead to ozone or smog formation. Smog chamber studies have shown that this is not the case. Furthermore, TDI should not be considered an ozone precursor. Overall, it can be concluded that no significant long-term or wide-ranging environmental effects would be expected from current emissions of TDI to air.