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No reliable studies on toxicity of Na2S or NaHS to soil organisms were identified. According to Column 2 of Annex IX of the REACH regulation, these studies do not need to be conducted if direct and indirect exposure of the soil compartment is unlikely. Because all identified uses are industrial indoor processes, no release of the substances to soil is expected. Further, since Na2S and NaHS are not expected to occur as such in soil because of hydrolysis and/or oxidation and/or precipitation processes, no terrestrial toxicty studies can be conducted using the compounds as such. One may consider toxicity of H2S, but H2S formation will only occur under reducing conditions, such as in waterlogged and/or organic-rich soils. Moreover, the dominant process in such soils will be sulfide precipitation, resulting in depletion of any dissolved sulfides present. Also, it must be kept in mind that the organisms present in such soils are often adapted to living in circumstances of fluctuating H2S concentrations. On the other hand, one may consider toxicity of sulfate, because in most soils, any sulfide released will be oxidized to the much less harmful sulfate, which is an essential nutrient for e.g. plants (reference can be made to the OECD SIDS for Na2SO4). However, it was decided only to present this approach for the aquatic compartment (water column) which is considered the most critical compartment for risk characterization.

Finally, no reliable studies on toxicity of Na2S or NaHS to birds were identified. One may consider the mammalian dataset for this, however, because it was demonstrated that sulfide has no potential for bioconcentration/bioaccumulation, it was considered not useful to evaluate secondary poisoning (for which the bird toxicity data are used) and therefore PNEC derivation based on data for mammals nor a testing proposal for toxicity to birds is needed.

No data on the toxicity of NaOH or Na2CO3 to soil organisms were identified. The alkalinity of the reaction mass (pH 13) may locally have acute ecotoxicological effects, but within soil, reactions with water and organic material should quickly neutralize the bases. Na2CO3 may contribute to the problematic alkalinity of soil, but the effect of an accidental local release is unlikely to be significant.