Reaction products of boric acid and calcium dihydroxide and lithium hydroxide

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

The UVCB - Reaction products of boric acid and calcium dihydroxide and lithium hydroxide (EC # 701-453-3) has structural similarities to two already established categories: lithium salts of the oxyacids of boron (B); and calcium salts of the oxyacids of boron (B). Dilithium tetraborate (EC# 234-514-3) (source substance #1) and calcium metaborate (EC# 237-224-5) (source substance #2) will be used to predict the properties for the target substance.


In the environment, all lithium/calcium borate substances in the categories rapidly dissociate and release the same common compound, boric acid as a result of relevant transformation pathways (e.g. hydrolytic, oxidative, digestive or metabolic) at environmentally relevant conditions (i.e., pH and concentration). This boric acid component of the salt is expected to drive the ecotoxicological and environmental fate properties.

Literature evidence is documented in the attached category approach document and states that several lithium and calcium borates are precursors of boric acid.

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]-. Therefore 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 and ecotoxicological 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).

Based on existing information sourced from the scientific and regulatory literature it is concluded that all the lithium/calcium borate substances in these categories are expected to react similarly in the environment, forming boric acid if exposed to water or moist soils in the environment. As a result, read-across to dilithium tetraborate is proposed for this endpoint for the REACH registration of Reaction products of boric acid and calcium dihydroxide and lithium hydroxide.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Conclusions:

In conclusion, the 96h-LC50 for Cyprinus carpio exceeded the analytically confirmed nominal concentration of 100 mg/L when exposed to dilithium tetraborate. Read-across is proposed for Reaction products of boric acid and calcium dihydroxide and lithium hydroxide

Executive summary:

In an OECD 103 study, the 96h-LC50 for Cyprinus carpio exposed to dilithium tetraborate exceeded the analytically confirmed nominal concentration of 100 mg/L. No mortality or other clinical effects were observed in this study.

 Based on existing information sourced from the scientific and regulatory literature it is concluded that all the lithium borate substances in this category are expected to react similarly in the environment, forming boric acid if exposed to water or moist soils in the environment.  As a result, Reaction products of boric acid and calcium dihydroxide and lithium hydroxidewill also cause no mortality or other clinical effects to Cyprinus carpio. A 96h-LC50 of >100 mg/L is also reported for Reaction products of boric acid and calcium dihydroxide and lithium hydroxide.

Description of key information

Based on existing information sourced from the scientific and regulatory literature it is concluded that all the lithium borate substances in this category are expected to react similarly in the environment, forming boric acid if exposed to water or moist soils in the environment.  As a result, Reaction products of boric acid and calcium dihydroxide and lithium hydroxidewill also cause no mortality or other clinical effects to Cyprinus carpio. A 96h-LC50 of >100 mg/L is also reported for Reaction products of boric acid and calcium dihydroxide and lithium hydroxide.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

100 mg/L