Sodium hydrogendifluoride

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification for Persistence

Sodium hydrogendifluoride is an inorganic substance and so the issue of biodegradation does not apply. The substance dissociates rapidly to its constituent ions in the aqueous environment, forming Na+, H+ and F- ions which are naturally ubiquitous in the terrestrial and aquatic compartments of the environment. As such sodium hydrogenfluoride does not satisfy the criteria for classification as persistent.

Classification for Bioaccumulation

No data is available for bioaccumulation of sodium hydrogendifluoride. However, the substance is considered to have a low potential for crossing biological membranes and dissociates fully to its constituent ions (Na+, H+ and F-) in aqueous environments. Data available for sodium and fluoride indicates that bioaccumulation will not occur and as the behaviour of these species is well characterised, no further information is required. As such sodium hydrogendifluoride is not considered to satisfy the criteria for classification as bioaccumulative.

Classification for Toxicity

The toxic effects of sodium hydrogendifluoride are considered to be primarily due to fluoride ions from dissociation of the substance. Tests carried out with an appropriate read-across substance found that no classification for acute or chronic toxicity is triggered based on the criteria set out in EU regulation 1272/2008 (CLP) or under Annex XII of REACH. As such, the substance is not considered toxic.

Likely routes of exposure:

No significant exposure is expected in the air compartment or through secondary poisoning. Background levels of fluoride in the marine compartment are expected to be greater than those arising from sodium hydrogendifluoride. Exposure to all other compartments is considered.