Registration Dossier
Registration Dossier
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EC number: 201-058-1 | CAS number: 77-78-1
Endpoint summary
Administrative data
Description of key information
Additional information
Photodegradation:
No valid information are available. However, as stated in the EU RAR (2002) DMS will be subject to gravitational settling and was out by rain as well as reaction with photochemically produced hydroxyl radicals. The calculated (QSAR) half-life time for this indirect photolysis is 84.3 days. The method of calculation is according to the TGD (EC 1996).
Hydrolysis:
Dimethyl sulphate hydrolyses in water. Reaction rate and type of hydrolysis products depend on pH and temperature. In neutral or acid medium methanol and sulphuric acid are formed, whereas under alkaline conditions the reaction products are methanol and monomethyl sulphate (room temperature) or methanol and sulphate (elevated temperature), respectively. Several estimates for the hydrolysis rate are reported in literature. The half-life at room temperature and pH 7 is about 24 hours; at room temperature and pH 10 it is about 86 seconds. Other observed degradation times are: >70 hours at 8°C, 14 hours at 23°C, and 70 min. at 40°C. In another study a half-life of 1.2 hours is reported for the hydrolysis of DMS under neutral conditions at 25°C. The EHC document (1985) mentions additional DT50 values of 4.5 h (temperature unknown) and 40 minutes (at 20°C), at neutral conditions. It should be noticed, that the high hydrolysis rate of the substance would lead to a high removal percentage of DMS in an STP in the present risk assessment. DMS will be regarded as readily biodegradable in industrial STPs.
Biodegradation:
According to a screening test on readily biodegradability performed in 1998 according to OECD 301E, the test substance in the test concentration of 100 mg/L reached the level of 10% (begin of the biodegradation) after 2 days. After 14 days a mean degradation rate of 97% and the plateau was reached. The pass level of a biodegradation > 70% was reached in a 10 [d]-window. Therefore, DMS could be regarded as readily biodegradable.
Distribution:
For the adsorption/desorption of dimethyl sulphate in a soil system a log Koc of 1.2 is calculated using QSAR calculation program EpiSuite v4.00 (KOCWIN v2.00). From this it can be concluded that DMS has a low adsorption potential and thus a high mobility/leaching potential. For the volatility of DMS from water to air a Henry constant of 0.41 Pa m3/mol is noted in the QSAR calculation program EpiSuite v4.00. This value is taken from an experimental database and was measured at a temperature of 25°C. This means that the compound shows no tendency to evaporate from water.
Accumulation:
On the basis of the high water solubility, the hydrolysis rate of DMS and the low calculated log Kow of 0.16, no bioaccumulation of DMS is expected.
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