Dilithium tetraborate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics, other

Remarks:

Expert report

Type of information:

other: Expert report

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Data source

Reference

Reference Type:

other: Expert report

Title:

Unnamed

Year:

2017

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Theoretical statement based on literature data.

Test material

Test material information

Constituent 1

Reference substance name:

Dilithium tetraborate

EC Number:

234-514-3

EC Name:

Dilithium tetraborate

Cas Number:

12007-60-2

Molecular formula:

B4Li2O7

IUPAC Name:

dilithium tetraborate

Test material form:

solid: bulk

Specific details on test material used for the study:

Identification: Dilithium tetraborate
Molecular formula: B4Li2O7
Molecular weight: 169.12
Chemical structure
CAS Number: 12007-60-2
EC number 234-514-3
Purity: 99.3%

Test animals

Details on test animals or test system and environmental conditions:

Not applicable.

Administration / exposure

Duration and frequency of treatment / exposure:

Not applicable.

No. of animals per sex per dose / concentration:

Not applicable.

Positive control reference chemical:

Not applicable.

Details on study design:

Not applicable.

Details on dosing and sampling:

Not applicable.

Statistics:

Not applicable.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

ORAL EXPOSURE - Dilithium tetraborate is very soluble in water (141.2 g/L) and is therefore expected to readily dissolve into the gastrointestinal fluids. Upon solution, the substance is expected to dissociate into lithium ions and a tetraborate ion. Before being absorbed, inorganic borates can 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. Taking all aspects into account, for risk assessment purposes, oral absorption of dilithium tetraborate is set at 100%.Absorbed lithium ions are expected to be excreted unchanged via urine.
DERMAL EXPOSURE - Based on existing evidence related to the very low uptake through intact skin of boric compounds, dermal absorption rate of 0.5% has been put forward for risk assessment purposes. However, it has been suggested that for borates, the absorption could be lower than 0.5%. Furthermore, since the substance is not corrosive or irritating to the skin, it is likely that skin integrity will remain intact upon exposure. The dermal absorption of dilithium tetraborate for risk assessment purposes is therefore set at 0.5%.
INHALATION EXPOSURE -It is possible that aerosols are formed which can enter the lungs. The deposition pattern in the lung can be determined based on its distribution, although shape and electrostatic properties can influence this as well. Since aerosols are expected to be very small, they may reach the thoracic region and the alveolar region of the respiratory tract. Overall it is expected that the exposure via inhalation will be very limited. However, if an aqueous aerosol of the substance reaches the lung regions, dilithium tetraborate is likely to dissolve in the mucus lining the respiratory tract and to get absorbed due to its high water solubility and moderate molecular weight. Based on the above data, for risk assessment purposes the inhalation absorption of aqueous dilithium tetraborate aerosols is set at 100%.

Details on distribution in tissues:

Based on the fact that the boron will be present uncharged and as a small molecule, even distribution of the ions throughout the soft tissues of the body is expected. Due to its water solubility, small size and inorganic nature, significant accumulation in adipose tissue is not expected.

Details on excretion:

Absorbed lithium ions are expected to be excreted unchanged via urine.

Metabolite characterisation studies

Metabolites identified:

not measured

Details on metabolites:

Not applicable.

Bioaccessibility (or Bioavailability)

Bioaccessibility (or Bioavailability) testing results:

Not applicable.

Applicant's summary and conclusion

Conclusions:

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.

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.