Lithium metaborate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Justification for type of information:

A toxicokinetic assessment was performed based on data available for dilithium tetraborate. Based on the physical/chemical properties of dilithium tetraborate, absorption factors for this substance are derived to be 100% (oral), 100% (inhalation of aqueous aerosols) and 0.5% (dermal absorption from aqueous solutions) for risk assessment purposes. The bioaccumulation potential is expected to be low.

As lithium metaborate has similar physicochemical properties ie. low vapour pressure and soluble in water then it is expected that the toxicokinetics assessment would be similar if not identical for lithium metaborate especially since all absorption factors derived were based on evidence for boric compounds such as boric acid. Both the inorganic borates, lithium metaborate and dilithium tetraborate, will be converted to boric acid at physiological pH in the aqueous layer on the surfaces of the mucosa. Boric acid is known to be readily taken up from the gastrointestinal tract in rats and humans, as demonstrated by experimental evidence in both human and animal studies, where more than 90% of the administered dose of borate was excreted as boric acid.

Sufficient evidence therefore exists to propose the same absorption factors for the toxicokinetics assessment. Read-across to dilithium tetraborate is proposed.

Materials and methods

Test material

Test material information

Constituent 1

Reference substance name:

Lithium metaborate

EC Number:

236-631-5

EC Name:

Lithium metaborate

Cas Number:

13453-69-5

Molecular formula:

BHO2.Li

IUPAC Name:

lithium metaborate

Applicant's summary and conclusion

Conclusions:

A toxicokinetics assessment was performed using the available data for diltihium tetraborate. Lithium metaborate is sufficiently similar in terms of physicochemical properties and behaviour upon absorption that the same absorption factors can be used.

Executive summary:

A toxicokinetic assessment was performed based on the available data of dilithium tetraborate. Based on the physical/chemical properties of dilithium tetraborate, absorption factors for this substance are derived to be 100% (oral), 100% (inhalation of aqueous aerosols) and 0.5 % (dermal absorption from aqueous solutions) for risk assessment purposes. The bioaccumulation potential is expected to be low.

As lithium metaborate has similar physicochemical properties ie. low vapour pressure and soluble in water then it is expected that the toxicokinetics assessment would be similar if not identical for lithium metaborate especially since all absorption factors derived were based on evidence for boric compounds such as boric acid.  Both the inorganic borates, lithium metaborate and dilithium tetraborate, will be converted to boric acid at physiological pH in the aqueous layer on the surfaces of the mucosa. Boric acid is known to be readily taken up from the gastrointestinal tract in rats and humans, as demonstrated by experimental evidence in both human and animal studies, where more than 90% of the administered dose of borate was excreted as boric acid.  

Sufficient evidence therefore exists to propose the same absorption factors for lithium metaborate of 100% (oral), 100% (inhalation of aqueous aerosols) and 0.5 % (dermal absorption from aqueous solutions) for risk assessment purposes.