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Sediment toxicity

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Diphosphorus pentaoxide is hygroscopic forming with water an aqueous solution of phosphorus oxyacids (primary hydrolysis) which are subject to further (secondary) hydrolysis to the end product phosphoric acid, H3PO4. Hydrolysis of P2O5in water under conditions relevant for ecotoxicological studies (100mg/L, 25°C) leads to slightly acidic solutions(pH 3.6) with the main product of tetraphosphoric acid. Further hydrolysis within the time frame of ecotoxicological studies is insignificant.


Under environmental conditions the hydrolysis products are available as different phosphate (Na, K, Ca). Phosphate and phosphorus are an essential nutrient of microorganisms, plants and animals. Phosphoric acid is readily utilizable by aquatic plants and microorganisms. Phosphorus compounds are an important component of living matter and all organisms contain a certain quantity; however, a toxicity on sediment living organisms is very unlikely due to natural metabolic processes for essential nutrients. It can be stated that a sediment toxicity test is not warranted. This statement given above is in line with the specific rule in 1907/2006/EC Annex X, section 9.5.1, column 2: “Long-term toxicity testing need not to be proposed, because the results of the chemical safety assessment indicate no need to investigate in further studies of the effects of the substance and/or the relevant degradation products on sediment organisms.”