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EC number: 231-633-2
CAS number: 7664-38-2
Literature data are available to assess the effects of phosphoric acid on fish. Studies are not performed to an OECD guideline but are considered ot be reliable for assessment (Klimisch 2) as part of a weight of evidence in accordance with Annex XI of Regulation (EC) No. 1907/2006 (REACH). These studies indicate that mortality as a result of phosphoric acid exposure is linked to the pH and not as a result of systemic toxicity.
A Median lethal pH (96h) of 3-3.25 for
Lepomis macrochirus (no guideline followed) has been derived.
All available studies show that mortality is
caused by low pH values. When adjusted to environmentally relevant pH
values, phosphoric acid does not cause acute adverse effects.
The study from Ellgaard and Gilmore 1982,
focuses on the pH effects caused by phosphoric acid. Different pH levels
have been tested in bluegill sunfish.
The pH induced by phosphoric acid which
caused 50% mortality was between 3.0 and 3.25, while no mortality was
observed at pH 3.5 or above after 96h exposure. At neutral pH 7.5 no
Similar results were obtained in the Alkahem
study: a median lethal pH of 3.58 in Aphanius dispar. The Korean study
showed a 96h-LC50 of phosphoric acid in Oryzias latipes of 75.1 mg/L,
but the pH was not adjusted to relevant environmental values. No
mortality was observed at 100 mg/L when the pH was adjusted.
The studies show that a pH caused by adding
phosphoric acid roughly between pH 3 (or lower) and 4 is critical for
fish. The Gueylard and Duval study showed that survival times increased
with increasing pH, and that this increase was more rapid at pH values
above 3.5. It can thus be concluded that it is the low pH which is
causing the toxic effects. Wallen et al. cited by Von Burg as well
described a study in which fish (Gambusia affinis) were exposed to both
phosphoric acid and turbidity (600 ppm of clay particles), and in which
phosphoric acid precipitated turbidity to levels below 25 ppm. The
median tolerance limit after 24, 48 and 96h exposure was 138 ppm (i.e.
about 138 mg/L). Townsend and Cheyne (1944) showed that exposure of
Oncorhynchus kisutch fingerlings to 20 ppm of phosphoric acid (i.e. pH
6.75) induced no mortality at relatively normal dissolved oxygen
concentrations (4.95 -8.15 ppm). However, when the dissolved oxygen
concentration was lowered to 1.50 ppm, phosphoric acid at 12.0 and 20.0
ppm induced 100% mortality, which is obviously caused by the combination
of the low dissolved oxygen concentration and the presence of increased
hydrogen ion concentrations.
As regulatory ecotoxicity tests need to be
conducted at pH 6-9, it can be expected that phosphoric acid will not
cause adverse effects to fish when in this pH range.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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