Zinc dipropionate

Endpoint summary

Description of key information

Metal carboxylates such as zinc dipropionate are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of zinc dipropionate in water (40.5 g/L at 30 °C), a complete dissociation of zinc dipropionate resulting in zinc ions and propionate ions may be assumed under environmental conditions. Since zinc ions and propionate ions behave differently in respect of biodegradation, a separate assessment of the environmental fate of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity. In brief, propionate, respectively propionic acid is readily biodegradable (according to OECD criteria).

The concept of “biodegradability” has been developed for organic substances and is not applicable to inorganic substances, including zinc. As a surrogate approach for assessing “degradability”, the concept of “removal from the water column” has been developed to assess whether or not a respective metal ion would remain present in the water column upon addition (and thus be able to exert a chronic effect) or would be rapidly removed from the water column. In this concept, “rapid removal” (defined as > 70% removal within 28 days) can be considered equivalent to “rapid degradation”. For zinc in water, information is available on the removal of zinc from the water column. The removal from the water column was modelled referring to the EUSES model parameters and different conditions of pH. Zinc is removed by > 70% under the reference conditions for the EU regional waters (EUSES) (see Mutch Associates, LLC, 2010a,b). Consequently, zinc is considered as equivalent to being ‘rapidly degradable in the context of classification for chronic aquatic effects.