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Environmental fate & pathways

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DD-lactide rapidly hydrolyses upon contact with water (hydrolysis half-life at 20 °C is ca. 1.45–3.0 hours), forming lactoyl lactic acid, which is further degraded to lactic acid. Therefore, the environmental fate of lactide can be understood in terms of lactic acid.

Physicochemical properties of enantiomers are essentially identical, except for those dependent on a chiral environment (e.g. optical activity, see e.g. Most if not all environmental fate processes take place in a non-chiral or 'racemic' environment, and thus will not discriminate between enantiomers. Therefore, albeit the above hydrolysis rates were determined for LL-lactide, they are equivalently applicable also to DD-lactide. L- and D-lactic acid are both ubiquitous constituents of biological systems and are produced and metabolised by many bacteria and other micro- and macro-organisms. Consequently, both L- and D-lactic acid are completely biodegradable, but this is also true for DD-lactide itself. Therefore, data for L-lactic acid are fully valid for D-lactic acid, and by proxy for DD-lactide.

Both DD-lactide and its hydrolysis product D-lactic acid will be present predominantly in aqueous compartments, neither of them will bioaccumulate or bioconcentrate, and DD-lactide is rapidly biodegraded, therefore not persistent.

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