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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Photochemical degradation in the upper atmosphere is expected to occur with a half-life of 19 hours. Therefore, concentration of methomyl in the air compartment and transport through it is not expected to be significant.  In a hydrolysis study, methomyl was unstable at all pH and temperature conditions; however, hydrolysis occurred at a more rapid rate at higher temperatures across the pH range tested. Based on these results, methomyl would be expected to hydrolyze in the environment. Exposure of aqueous test substance solution at concentrations of 10 and 100 ppm to artificial sunlight (peak sensitivity at approximately 365 nm, and intensity equivalent to approximately half that of typical summer sunshine at noon) yielded half-lives of approximately 5.5 and 2 days, respectively. In a photo-transformation study in soil, the test substance decomposed with a half-life of 34 days to form acetonitrile, the only detected radioactive decomposition product.

Methomyl is not ready biodegradable according to a study conducted by OECD 310B and EU Method C.5. In an OECD 309 study, the DT50 was 284 days in surface water, non-sterile and > 1 year in surface water, sterile. In a water/sediment study conducted according to OECD 308, the DT50 in Tilt, sandy loam was 20.5 days while the DT50 in Wabasha loam was 2.5 days. Biodegradation in soils (DT50 values) ranged from 4-11.6 days in aerobic studies and was 14 days in an anaerobic metabolism study. The test substance was weakly adsorbed to all five soils tested.

The test substance that was adsorbed was poorly desorbed with mean totals (DT) of 1-30% of that adsorbed, desorbed. This possibly reflects the potential of the test substance binding preferentially to soil at limited sites through chemical processes. Koc values ranged from 16.4 -50.8 mL/g at 20 degC.

Additional information