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Environmental fate & pathways

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Phosphoric acid, potassium salt (2:3), dihydrate (CAS No. 66922-99-4) is soluble (water solubility, 750 g/L) and will dissociate completely in water, mainly into PO4-3and K+ ions. Due to the inorganic nature of this substance, the biodegradation concept is not applicable and therefore it is considered not relevant. Potassium and phosphate are essential elements present naturally in the environment and in living organisms. These organisms possess internal mechanisms to regulate them and thus, bioaccumulation of this substance in biota is not expected. As phosphoric acid, potassium salt (2:3), dihydrate will be found in a dissociated form in aqueous solutions, its adsorption potential is assumed to be low. Based on its vapour pressure value (1.9 x 10-8 hPa at 25°C), the substance can be considered as non volatile.

Regarding the products of the dissociation of this substance, certain information needs to be considered. An excess of phosphates in aquatic ecosystems may lead to eutrophication problems. Due to an increase in nutrient content, algae species growth is enhanced. Once those algae die, the decomposition process implies a high consumption of O2, which can be depleted and unavailable for fishes and other aquatic fauna (OECD SIDS, 2007). The European Directive on Integrated Pollution Prevention and Control (96/61/EC) includes phosphates in Annex III, where substances for which fixed emission limits should be considered in industrial wastewater are stated. Directives 1991/271 (Urban Waste Water Treatment Directive) and 2000/60 (EU Water Framework) also establish the need for limiting phosphates in municipal waste water plants.