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Environmental fate & pathways

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Biodegradation:

Not biodegradable in soil and water under non-adapted conditions. Biodegradable after adaptation and methane enrichment.

Different investigations have been undertaken to study the biodegradability of 1,2-dichloroethane. However, there are no standardized screening studies on ready or inherently biodegradation available. In the various non-guideline studies which were mostly conducted according to generally acceptable principles it could be shown that the material is not biodegradable when non-adapted, non-acclimated conditions were used. In contrast biodegradation occurred when adapted or induced micro-organisms were used. Under abiotic conditions biodegradation of 1,2 -dichloroethane is too slow to be an important environmental fate process.

Based on both the water solubility and high volatility, adsorption to soil and sediments is not expected, which is supported by an experimentally determined KOC-value of 33 for silt loam. The substance rapidly percolates through sandy soil.

Taking into consideration the measured octanol/water partition coefficient of 1.45, no potential for bioaccumulation/bioconcentration can be identified. This is supported by calculated and experimentally determined bioconcentration factors of 2.

1,2-Dichloroethane is predominantly distributed in air (95 %) and only in minor portion into water (<4.8 %) while all other compartments such as soil, sediment, suspended matter and biota make no substantial contributions. The relative high degree of distribution into air is based on the high vapour pressure and the high volatility of the substance from water as indicated from the calculated and experimentally determined Henry’s Law constants of 95.7 Pa *m3/mol and 149 Pa * m3/mol, respectively.

Based on the high vapour pressure and volatility of the substance, 1,2-dichloroethane entering aquatic systems would be transferred to the atmosphere through volatilisation. Results of laboratory experiments yielded half-lives in water ranging from 0.5 – 4 hours. A half-life of 1.4 hours for the removal from running river water was found in outdoor experiments conducted under controlled conditions. These results indicate that 1,2 -dichloroethane is expected to be rapidly removed from aqueous media by volatilisation. Nevertheless the low affinity for soil may pose a risk of groundwater contamination.

 

Due to its chemical structure, the substance will not undergo hydrolysis in water. Photodegradation by direct sun-light: DT50 values for degradation in air are estimated by calculation to be in the range 42 to 73 days. The products arising from photo-oxidation are carbon dioxide and hydrogen chloride. Field measurements confirmed that the photo-degradation in the atmosphere prevents the global distribution and the atmospheric enrichment of emissions, released by industry mainly in the northern hemisphere.