Dilithium tetraborate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

other: theoretical statement

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline followed

Principles of method if other than guideline:

Theoretical statement based on literature data.

GLP compliance:

no

Analytical monitoring:

no

Details on sampling:

Not applicable

Buffers:

Not applicable

Estimation method (if used):

Not applicable

Details on test conditions:

Not applicable

Number of replicates:

Not applicable

Preliminary study:

Not applicable

Test performance:

Not applicable

Transformation products:

not measured

Key result

Remarks on result:

not measured/tested

Remarks:

Based on existing information sourced from the scientific and regulatory literature it is concluded that hydrolysis testing is not necessary for dilithium tetraborate. These substances are expected to form boric acid if exposed to water or moist soils in the environment. Boric acid is extremely stable and is not susceptible to hydrolysis in environmental media.

Details on results:

There are many boron substances (e.g. borate salts, boron halides) that release boric acid as a result of relevant transformation pathways (e.g. hydrolytic, oxidative, digestive or metabolic) at environmentally or physiologically relevant conditions (i.e., pH and concentration); which are considered to be precursors of boric acid.

In the Environment and Climate Change Canada (ECCC) Health Canada Draft Screening Assessment of Boric acid, its Salts and its Precursors it was concluded that several lithium and calcium borates are precursors of boric acid (ECCC, 2016; ECCC, 2014).

In the Inventory Multi-Tiered Assessment and Prioritisation (IMAP) Environmental Tier II Assessment for Boric Acid and Precursors to Boric Acid performed by the Australian National Industrial Chemicals Notification and Assessment Scheme (NICNAS), it was concluded that several sodium salts of boric acid are expected to dissociate and/or hydrolyse to release boric acid at neutral pH (NICNAS, 2017). It is reasonable to draw the same conclusion to lithium borate in terms of its expected dissociation/transformation to boric acid in contact with water.

Boric acid, [B(OH)3], is a very weak, monobasic acid that acts as a Lewis acid by accepting a hydroxyl ion to form the borate anion, [B(OH)4]-. At higher concentrations and pH levels greater than 9.2, the borate anion [B(OH)4]- becomes predominant.

B(OH)3 + 2H2O¿[B(OH)4]- + H3O+

Therefore, at the near neutral pH of most environmental systems and at low concentrations (<0.025 mol B/L), the neutral mononuclear species (B(OH)3) will dominate and only a small proportion of boron will exist as the borate monoanion, B(OH)4- (WHO, 1998).

In the Transitional Annex XV dossier for Boric Acid (Boric acid crude natural) submitted by Austria, the following statement is provided for the hydrolysis endpoint: “Boric acid is an inorganic compound and does not have any chemical bonds prone to hydrolysis. Hydrolysis is therefore not a relevant degradation pathway for boric acid under environmentally relevant conditions”. Therefore, once dilithium tetraborate has transformed to boric acid in water, no further hydrolysis is anticipated.

Based on existing information sourced from the scientific and regulatory literature it is concluded that hydrolysis testing is not necessary for dilithium tetraborate. These substances are expected to form boric acid if exposed to water or moist soils in the environment. Boric acid is extremely stable and is not susceptible to hydrolysis in environmental media.

References

Environment and Climate Change Canada (2016). Draft Screening Assessment Boric Acid, its Salts and its Precursors. Available via: http://www.ec.gc.ca/ese-ees/default.asp?lang=En&n=2A581398-1#toc0822

Environment Canada and Health Canada. 2014. Supporting documentation: Scoping Document for Boron-containing substances. Gatineau (QC): Environment Canada. Information in support of the Draft Screening Assessment for Boric acid, its salts and its precursors.

NICNAS 2017. Environment Tier II Assessment for Boric Acid and Precursors to Boric Acid. Available via:
https://www.nicnas.gov.au/chemical-information/imap-assessments/imap-assessments/tier-ii-environment-assessments/boric-acid-and-precursors

WHO (1998). Environmental health criteria 204–Boron. Geneva. Available via: http://www.inchem.org/documents/ehc/ehc/ehc204.htm.

Validity criteria fulfilled:

not applicable

Conclusions:

Based on existing information sourced from the scientific and regulatory literature it is concluded that hydrolysis testing is not necessary for dilithium tetraborate. These substances are expected to form boric acid if exposed to water or moist soils in the environment. Boric acid is extremely stable and is not susceptible to hydrolysis in environmental media. No futher testing is therefore required.

Executive summary:

A theoretical statement was produced in order to satisfy the Annex VIII (Tonnage =10 t/y) REACH requirements relating to hydrolysis testing as a function of pH. The hydrolysis test is designed to provide information on abiotic degradation that can help in classification, persistence testing and in determining the fate of a substance in environmental surface waters.

The hydrolysis testing requirement under EU REACH may be waived only if the substance is readily biodegradable or the substance is highly insoluble in water. However, the test item does not meet either of these waivers. However, based on existing information sourced from the scientific and regulatory literature it is concluded that hydrolysis testing is not necessary for dilithium tetraborate. These substances are expected to form boric acid if exposed to water or moist soils in the environment. Boric acid is extremely stable and is not susceptible to hydrolysis in environmental media.  No futher testing is therefore required.

Description of key information

Based on existing information sourced from the scientific and regulatory literature it is concluded that hydrolysis testing is not necessary for dilithium tetraborate. These substances are expected to form boric acid if exposed to water or moist soils in the environment. Boric acid is extremely stable and is not susceptible to hydrolysis in environmental media.  No further testing is therefore required.