Orthophosphoric acid

Long-term toxicity to fish

Description of key information

This endpoint is covered by a waiver in accordance with Annex IX, section 9.1.6, column 2 of Regulation (EC) No. 1907/2006 (REACH) and two supporting studies (Jagoe et al., 1984 and Menendez, 1976) on another acid, namely sulfuric acid. These supporting studies provide information regarding the effects of pH on the early life stages of fish.

Additional information

Supporting data:

Jagoe et al. (1984) studied the effects of reduced pH (pH 3-6) induced by sulphuric acid on three life stages (eggs, sac fry and yearlings) of Salvelinus alpinus. Yearlings continuously exposed up to 19 days did not show mortality at pH 4.5 and above. Sac fry continuously exposed for 9 days did not show mortality at pH 5.0 and above. Eggs continuously exposed for 8 days showed significant pH-induced mortality up to pH 5.0. The study showed that yearlings are most resistant to acid stress while eggs are most sensitive.

Menendez (1976) studied the effects of reduced pH (pH 4.5-7.1) induced by sulfuric acid on all developmental stages of Salvelinus fontinalis. Adult fish were exposed for up to 5 months. Embryos from these exposed fish were also exposed and checked for viability and hatchability. Alevins of exposed and non-exposed fish were exposed for 90 days. At pH 4.5 all adult fish died. Total egg production was not affected. At pH 5.0 viability of eggs was significantly decreased compared to controls. Hatchability of embryos was reduced at all pH levels below pH 6.5. The study indicated that continuous exposure to pH levels below 6.5 result in significant reductions in hatchability and growth.

It can be concluded that long-term effects are caused by reduced pH, similar as in the acute ecotoxicity tests. At normal environmental conditions, the pH will be buffered. Moreover, industry is not allowed to release acid wastewater streams to the aquatic environment. Release of phosphoric acid would also negatively influence the conditions in the sewage treatment plant which is not desirable. In the case of phosphoric acid release to the environment, this will be peak exposures due to accidental releases, rather than long-term continuous releases. It is therefore not needed to investigate further the long-term effects of phosphoric acid (or other acids) to fish and other aquatic species. Furthermore, a lot of general studies have been published in the past on long-term and short-term effects to aquatic species induced by pH (hydronium ions) (e.g. the book Acid Toxicity and Aquatic Animals by Morris, Taylor, Brown and Brown, 1989, Cambridge University Press). Many fish species can survive environmental pH values of 4.5 and above, due to calcium reducing the permeability of the gills to other ions (H+ ions). Adaptation may also play a role in surviving low pH levels.