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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

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 2007 of sodium hydroxide, section 3.1.3, page 24).

If emitted to the air as an aerosol in water, NaOH will be rapidly neutralised as a result of its reaction with CO2 (or other acids), as follows (EU RAR 2007, section, 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 neutralised NaOH will largely end up in soil and water.

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