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 emissions of NaOH mainly apply to (waste)water. Furthermore, the high water solubility and very low vapour pressure indicate that NaOH will be found predominantly in water. In water (including soil or sediment pore water), NaOH is present as the sodium ion (Na+) and hydroxyl ion (OH-), as solid NaOH rapidly dissolves and subsequently dissociates in water (EU RAR 2007of sodium hydroxide, section 3.1.3, page 24).

If emitted to the air as an aerosol in water, NaOH will be rapidly neutralized as a result of its reaction with CO2 (or other acids), as follows (EU RAR 2007, section 3.1.3.4, page 26):

NaOH + CO2 -> HCO3- + Na+

Subsequently, the salts (e.g. sodium(bi)carbonate) will be washed out from the air (US EPA, 1989; OECD, 2002 ). Thus, atmospheric emissions of neutralized NaOH will largely end up in soil and water.

If emitted to soil, sorption to soil particles will be negligible (EU RAR 2007, section 3.1.3.3, page 26). Depending on the buffer capacity of the soil, OH- will be neutralized in the soil pore water or the pH may increase.