Feropur

Endpoint summary

Additional information

When in contact with water, the constituents of Feropur will be degraded within seconds to Na⁺,OH^-and H₂. Consequently, Na₂O and NaH are considered to be too short-living and hence irrelevant for the assessment of environmental and toxicological effects. Based on the very quick and complete degradation of Na₂O and NaH to NaOH, the risk assessments for the environment and humans are based on the properties of NaOH and Na₂CO₃.

This approach was discussed with ECHA (see attached document: "Strategy paper Feropur ECHA 090813.pdf"). ECHA agreed on this approach (see attached document "reply ECHA 090902.pdf").

The hazards of NaOH and Na₂CO₃ for the environment are caused by the hydroxyl ion and carbonate ion, respectively, and hence by an effect on the pH, i.e., both ions will increase the pH. However, the impact on the pH-effect of the carbonate ion is much weaker than the impact of the hydroxyl ion. In the SIDS dossier of sodium carbonate (SIDS dossier for sodium carbonate, 2002, Table 1, page 10, see attached document) it is outlined that 603 mg sodium carbonate/L are needed to increase the pH of distilled water to a pH of 11. To cause the same effect with sodium hydroxide, only 40 mg sodium hydroxide/L is needed (SIDS dossier for sodium hydroxide, 2002, Table 1, page 10, see attached document). Hence, the effects of sodium carbonate are about 15 times weaker than for sodium hydroxide. In addition, the concentration of sodium carbonate is only about 5% in Feropur. When in contact with water, the degradation products consists to about 95 % of sodium hydroxide and about 5% of sodium carbonate (see attached document "Strategy paper Feropur ECHA 090813.pdf"). When multiplying the concentration with the efficiency of sodium carbonate relative to sodium hydroxide (1/15th), i.e., 5%*1/15, the impact of sodium carbonate in Feropur would be about 0.3% when compared to the effect of sodium hydroxide in Feropur. Na₂CO₃ is registered as food additive E500i and may be added quantum satis to food and is therefore considered to be a substance of “low priority".

Based on the same mode of action and the much weaker effect of sodium carbonate in combination with the much lower content of sodium carbonate in Feropur when compared to sodium hydroxide, it can be concluded that the risk of Feropur is sufficiently described by the risk resulting from sodium hydroxide alone.

The available data indicate that NaOH concentrations of 20 to 40 mg/L may be acutely toxic to fish and invertebrates (single species tests). Data on pH increases due to the addition of these amounts of NaOH in the used test waters are lacking. In waters with a relatively low buffering capacity, NaOH concentrations of 20-40 mg/L may result in a pH increase with one to several pH units (EU RAR, 2007;section 3.2.1.1.3, page 30).

The OECD SIDS (2002) assigned a low code of reliability ('invalid' or 'not assignable') to all available tests, as in general the tests were not conducted according to the current test guidelines (EU RAR, 2007; section 3.2.1.1.4, page 30). Furthermore, in many tests reports there were no data on pH, buffer capacity and/or test medium composition, although this is essential information for toxicity tests with NaOH. This is the most important reason why most of the tests were considered 'invalid'. Despite this lack of valid data, there is no need for additional aquatic toxicity testing with NaOH, as all available tests resulted in a rather small range of toxicity values (acute toxicity tests: 20 to 450 mg/L; chronic toxicity test: > or = 25 mg/L) and there are sufficient data on the pH ranges that are tolerated by major taxonomic groups.

Moreover, a generic PNEC cannot be derived from single-species toxicity data for NaOH, as the pH of natural waters as well as the buffer capacity of natural waters show considerable differences and aquatic organisms/ecosystems are adapted to these specific natural conditions, resulting in different pH optima and pH ranges that are tolerated (EU RAR, 2007; section 3.2.1.1.4, page 30). According to the OECD SIDS (2002), a lot of information is available about the relationship between pH and ecosystem structure and also natural variations in pH of aquatic ecosystems have been quantified and reported extensively in ecological publications and handbooks.