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Environmental fate & pathways

Phototransformation in air

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Description of key information

Parent compound methyl chloroformate (CAS 79 -22 -1): After evaporation or exposure to air, the substance will be slowly degraded by photochemical processes. This estimate refers to dry air. In mist, rain, droplets and aerosols, hydrolysis will be the major fate process of the chloroformate due to the short half-life in aqueous solution. Therefore this estimate may be of low relevance.

Hydrolysis product methanol (CAS 67 -56 -1): After evaporation or exposure to air, the substance will be slowly degraded by photochemical processes.

Key value for chemical safety assessment

Additional information

Parent compound methyl chloroformate:

Based on an estimated OH radical rate constant of 2.176E-13 cm3/(molecule*sec), the half-life of methyl chlorformate was calculated to be 73.7 days (conditions: sensitiser for indirect photolysis: OH; 0.5 E06 OH/cm3, 24-h d; BASF SE, 2019). Based on the EPI Suite calculation the substance will be slowly degraded by photochemical processes, after evaporation or exposure to air. This estimation refers to dry air. In mist, rain, droplets and aerosols, hydrolysis will be the major fate process of the chloroformate due to the short half-life in aqueous solution. Therefore this estimate may be of low relevance.

Hydrolysis product methanol:

Based on a measured OH-radical rate constant of 9.32E-13 cm3/(molecule*sec), the half-life of methanol was calculated to be 17.2 days (conditions: sensitiser for indirect photolysis: OH; Atkinson, 1989; peer-reviewed data OECD, 2004). Based on the available measured data the substance will be slowly degraded by photochemical processes, after evaporation or exposure to air.

 QSAR-disclaimer:

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met.

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

For the assessment of methyl chloroformate (CAS 79-22-1) (Q)SAR results were used for phototransformation in air.

The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint is sufficiently covered and suitable for risk assessment.

Therefore, further experimental studies on phototransformation in air are not provided.

Conclusion:

Based on the available calculated and experimental data for the parent itself and int metabolite product, it can be concluded, that both substances will be slowly degraded by photochemical processes, after evaporation or exposure to air.