Germanium dioxide

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Remarks:

Test according to state-of-the-art operating procedures for testing of metal bioelution.

Objective of study:

bioaccessibility (or bioavailability)

Qualifier:

according to guideline

Guideline:

other: ASTM D5517-07: Standard Test Method for determining the extractability of metals from art materials - ASTM, 2007 (American Society for Testing and Materials).

Principles of method if other than guideline:

The release/dissolution of germanium from germanium(IV) oxide in simulated gastric fluid was measured. The resulting value is termed bio-accessibility, and is defined as the fraction of a substance that is soluble under physiological conditions and therefore potentially available for absorption into systemic circulation. The simulated gastric fluid represents an exposure-relevant exposure route (oral exposure). The compound was introduced as powder in a test item / solution ratio of 200 mg/L during 2 hours.

GLP compliance:

yes

Preliminary studies:

not applicable

Type:

other: bioaccessibility

Results:

gastric fluid (0hours): as %Ge released of total Ge content: 0.09

Type:

other: bioaccessibility

Results:

gastric fluid (1hours): as %Ge released of total Ge content: 10.5

Type:

other: bioaccessibility

Results:

gastric fluid (2hours): as %Ge released of total Ge content: 23.3

Details on absorption:

not applicable

Details on distribution in tissues:

not applicable

Details on excretion:

not applicable

Metabolites identified:

not measured

Details on metabolites:

not applicable

Bioaccessibility (or Bioavailability) testing results:

gastric fluid (0hours): as %Ge released of total Ge content: 0.09
gastric fluid (1hours): as %Ge released of total Ge content: 10.5
gastric fluid (2hours): as %Ge released of total Ge content: 23.3

Germanium dioxide, loading 0.2 g/L (= 5.90 m²/L surface loading)
		2-h gastric at pH 1.2
Analyte		xavg± sbetween	CV
germanium (Ge)	dissolution	32.3 ±1.3 mg/L	4%
	absolute Ge release	162 ± 7 mg/g	4%
	% of total availableGeeluted	23.3%
	Ge release/surface	27.4 mg/m²

x_avg= average of 3 test vessels (blank corrected, if theblankvalue is > reporting limit, otherwise blank assumed as 0)

s_between= standard deviation

CV= Coefficient of Variation (%)

Conclusions:

The dissolution in gastric fluid is used to estimate bioavailability after oral exposure. Bio-elution test according to state-of-the-art procedures, useful for determining dissolution capacity of In in gastric fluid.
Interpretation of results: low bioaccessibility of Ge from germanium(III) oxide.

Executive summary:

During this study on Germanium dioxide at a loading of 0.2 g/L in simulated gastric fluid (pH 1.2), it was shown that a significant amount of germanium (average dissolved germanium concentration of 32.3 ± 1.3 mg/L Ge or 162mg/g Ge with a between-vessel variation of 4% (CV=4%)) was measured after 2 hours of extraction. Based on the specific surface area of Germanium dioxide (i.e. 5.90 m²/g test item), a germanium release per surface 27.4 mg/m² was calculated. Based on the germanium content in the test item (69.4%) and the average dissolved germanium concentration, a germanium release of 23.3% could be calculated.

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

absorption

distribution

toxicokinetics

Qualifier:

no guideline followed

Principles of method if other than guideline:

Absorption, transport, distribution, storage and excretion of inorganic germanium in albino rats.
GeO2: Gastrointestinal absorption and transport and elimination of GeO2 by the blood after oral administration

GLP compliance:

not specified

Radiolabelling:

no

Species:

rat

Strain:

other: albino

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: no information
- Age at study initiation: no information
- Weight at study initiation: no information
- Fasting period before study: 36hrs
- Housing: well ventilated cages
- Individual metabolism cages: no information
- Diet (e.g. ad libitum): no information
- Water (e.g. ad libitum): no information
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS : no information
- Temperature (°C):
- Humidity (%):
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light):

Route of administration:

oral: gavage

Vehicle:

water

Duration and frequency of treatment / exposure:

single dose

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Remarks:

rats of 200g are fed 10 mg GeO2 by stomach tube

Control animals:

not specified

Type:

absorption

Results:

rapid absorption after gavage (73.6% after 4h and 96.4% after 8h)

Type:

distribution

Results:

uniformly distributed between erythrocytes and plasma (2:3) and not bound to plasma proteins. Not deposited selectively but widely distributed among all the organs.

Metabolites identified:

not measured

Details on metabolites:

not applicable

Conclusions:

Germanium is relatively inert metabolically and are consonant with its remarkably low toxicity
Interpretation of results : low bioaccumulation potential based on study results

Executive summary:

Metabolic studies have been conducted of the absorption, transport, distribution, storage and excretion of inorganic germanium (GeO2 and sodium germanate) in albino rats.

The analytical data demonstrate that germanium is rapidly absorbed after oral, subcutaneous, intramuscular or intraperitoneal administration.

When injected directly into the systemic circulation or absorbed following oral or parenteral administration, it is transported unbound by plasma proteins and is rapidly eliminated from the blood stream.

Germanium (sodium germanate) is not deposited selectively but is widely distributed among all the organs. It is not retained or stored by any tissue even after many weekly doses, but is rapidly excreted via the urine and feces, the kidney bein the main excretory organ.

Reference 3

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

distribution

toxicokinetics

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Principle of test: investigation of the kinetics of germanium dioxide (GeO2) after single dose exposure; investigation of tissue distribution in a repeated exposure study (4wk)

GLP compliance:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
Germanium dioxide [germanium (IV) oxide, 99.999% pure, Showa Chemicals, Tokyo, Japan]

Radiolabelling:

no

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: no information
- Age at study initiation: no information
- Weight at study initiation: 300-350 gr
- Housing: in non-restrained cages
- Diet: normal diet containing no germanium free of access
- Water: fresh water containing no germanium free of access
- Acclimation period: no information

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22
- Humidity (%): no information
- Air changes (per hr): no information
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: double-distilled water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:

GeO2 was dissolved in double-distilled water

Duration and frequency of treatment / exposure:

singe dose exposure and repeated dose exposure study for 4 weeks

Dose / conc.:

100 mg/kg bw/day

Remarks:

in a single dose exposure study and in a 4 weeks repeated dose exposure study

No. of animals per sex per dose / concentration:

total of 36 rats used in the whole study: 6 rats assigned to the single dose exposure study and 30 rats for the repeated dose exposure study (15 exposed and 15 controls)

Control animals:

yes, concurrent vehicle

Positive control reference chemical:

no

Details on study design:

- Dose selection rationale: Based on data of published data Matsumuro et al 1993 showing germanium neuropathy could be induced in rats by supplying 100mg/kg BW GeO2, 100 mg/kg BW was selected to study the kinetics of GeO2

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled : blood, tissues: brain cortex, lung, heart, liver, kidney, sciatic nerve, and gastrocnemius muscle
- Time and frequency of sampling:
single dose exposure group study: Blood samples of 1 ml were collected from rat’s tail artery, respectively before feeding and at 0.25, 0.5, 1, 2, 4, 8, 12, and 24 h after GeO2 administration
repeated exposure group and control group study: Blood samples of 1 ml were also collected from rat’s tail artery under ether anesthesia, both at the moments of pre-exposure and just before sacrifice 4 weeks later.

Statistics:

The statistical analysis of results was performed with student’s t-test.

Type:

distribution

Results:

GeO2 accumulated especially in the peripheral nerves and kidneys

Test no.:

#1

Toxicokinetic parameters:

Cmax: 15.5 µg/ml

Remarks:

mean maximum concentration in serum

Test no.:

#1

Toxicokinetic parameters:

half-life 1st: 2.3 hours

Remarks:

mean elimination half-time

Test no.:

#1

Toxicokinetic parameters:

half-life 1st: 0.7 hours

Remarks:

mean absorption half time

Metabolites identified:

not measured

Conclusions:

Lin et al (1999) reported the kinetics of GeO2 in male Wistar rats after the oral administration of a single dose (100mg/kg) and found that maximal mean serum concentration was achieved in 0.7 hour and the mean elimination half-time was 2.3 hours. Lin et al, also conducted a multiple dose for 4 weeks and found highest concentrations of Ge in peripheral nerves and kidneys.

Executive summary:

The kinetics of germanium dioxide (GeO2) in single dose and repeated exposures were investigated in male Wistar rats. In the single dose GeO2 (100 mg:kg BW, p.o.) exposure study, values of several kinetic parameters were shown as follows, a maximum concentration in serum of 15.5 +/- 0.7 µg:/ml (mean +/-S.E.M.), an absorption half-life of 0.7 +/- 0.1 h (mean +/- S.E.M.), an elimination half-life of 2.3 +/-0.5 h (mean+/-S.E.M.), a distribution of the central compartment Vp (3.1 +/- 0.3 l, mean +/- S.E.M.), and the apparent volume of distribution of the tissue compartment Vt (8.5 +/- 2.9 l, mean +/-S.E.M.). In the repeated exposure study, 730 +/- 92 mg GeO2 in 1 l double-distilled H2O (100 mg:kg:day) was given daily to rats for 4 weeks (p.o.). After sacrificing the rats, the analysis of tissue distribution showed that GeO2 was accumulated in some important organs or tissues in the body, especially the peripheral nerves and kidney. These results indicate that GeO2 could be absorbed rapidly but had a longer elimination half-life in rats. In addition, GeO2 was accumulated especially in the nerves and kidney following long-term exposure.

Reference 4

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Principle of test: Three groups of rats were treated with a 3-h topical application of hydrophilic ointment containing graded level of neutralized GeO2 (pH 7.4): 0,
0.21 and 0.42 mg GeO2/g. Germanium concentration in blood and tissues sampled from rats after topical application of inorganic germanium was measured by inductively coupled plasma-mass spectrometry

GLP compliance:

yes

Species:

rat

Strain:

Fischer 344

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Japan SLC Inc., Shizuoka, Japan.
- Age at study initiation: 4-week-old
- Weight at study initiation: 50–70 g (mean 56.8 g, standard deviation 3.5 g
- Fasting period before study: no
- Housing: kept individually in stainless steel cages with raised wire bottoms
- Individual metabolism cages: yes
- Diet: free access to AIN-93G diet
- Water: free access to deionized water
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS: no information

Type of coverage:

not specified

Vehicle:

other:

Duration of exposure:

3h

Doses:

0, 0.21 mg/g and 0.42 mg/g

No. of animals per group:

6

Control animals:

yes

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions:
Preparation of inorganic germanium ointment:
Hydrophilic ointment containing neutralized GeO2 (inorganic germanium ointment) was prepared as follows. GeO2 of 2.5 g was stirred with excess amount of sodium hydroxide in deionized water (MilliQ, Millipore Co.) for hydrolysis. The alkaline solution
containing hydrolyzed GeO2 was neutralized with hydrochloric acid to give a solution with pH 7.4. Purified water was added to obtain 2.5 g/L neutralized GeO2 solution (1.735 g of elemental germanium/L). To prepare inorganic germanium ointment containing 0.42 mg GeO2/g, 3 mL of 2.5 g/L neutralized GeO2 solution was added to 15 g of hydrophilic ointment (Yoshida Pharmaceutical Co., Saitama, Japan) concordant to Japan Pharmacopoeia that contains 250 g white petrolatum, 200 g stearylalcohol, 120 g propyleneglycol, 40 g polyoxyethylene (60) hydrogenated castor oil, 10 g monostearylglycerine, 1 g methyl p-hydroxybenzoate, 1 g propyl p-hydroxybenzoate, and 378 g purified water per 1000 g. They were thoroughly mixed with a Teflon-coated ointment spatula on a 30 cm x 30 cm square polyvinyl chloride board. Similarly, 1.5 mL of 2.5 g/L neutralized GeO2 solution, 1.5 mL purified water, and 15 g hydrophilic ointment was mixed to obtain inorganic germanium ointment containing 0.21 mg GeO2/g.

APPLICATION OF DOSE: topical; Polyvinylidene chloride food wrap (Saran Wrap, Asahi Kasei Home Products Co., Tokyo, Japan) was cut into 2 cm x 2 cm square sheets and attached on cotton gauze by adhesives (Alonalpha, Toa Gosei Chemical Industry, Tokyo, Japan). 2 g of inorganic germanium ointment or blank ointment were spread on the polyvinylidene chloride sheet attached on cotton gauze for applying to the hair-removed skin.

VEHICLE
negative control: 3 mL purified water was mixed with 15 g hydrophilic ointment to prepare blank ointment.


TEST SITE:
A patch of hair approximately 3 x 4 cm from the dorsal abdominal surface along the spinal axis was clipped with an animal hair clipper. The remaining hair was removed with a depilatory cream (Epilat, Kanebo, Tokyo, Japan). The animals were
washed by warm tap water, and their fur was wiped by a towel and dried by a hair dryer. After overnight withdrawal of diets, the hydrophilic ointment containing neutralized GeO2 (inorganic germanium ointment) spread on the polyvinylidene chloride
sheet attached on cotton gauze was applied to the rat skin re-covered with short hair (approximately 1 mm length) after hair removal.

ANALYSIS
- Method type(s) for identification : Germanium concentration in the sample solution was measured by inductively coupled argon plasma-mass spectrometry (ICPM-8500, Shimadzu, Co., Kyoto, Japan).

Signs and symptoms of toxicity:

not examined

Dermal irritation:

not examined

Time point:

3 h

Dose:

0.21 mg/g

Parameter:

amount

Remarks:

in plasma

Absorption:

ca. 5.5 other: ng/g

Remarks on result:

other: average value in plasma based on reported graphs

Time point:

3 h

Dose:

0.21 mg/g

Parameter:

amount

Remarks:

in liver

Absorption:

ca. 6.4 other: ng/g

Remarks on result:

other: average value in liver based on reported graphs

Time point:

3 h

Dose:

0.21 mg/g

Parameter:

amount

Remarks:

in blood

Absorption:

ca. 3.8 other: ng/g

Remarks on result:

other: average value in blood based on reported graphs

Time point:

3 h

Dose:

0.21 mg/g

Parameter:

amount

Remarks:

in kidney

Absorption:

ca. 18 other: ng/g

Remarks on result:

other: average value in kidney based on reported graphs

Time point:

3 h

Dose:

0.42 mg/g

Parameter:

amount

Remarks:

in plasma

Absorption:

ca. 8.8 other: ng/g

Remarks on result:

other: average value in plasma based on reported graphs

Time point:

3 h

Dose:

0.42 mg/g

Parameter:

amount

Remarks:

in liver

Absorption:

ca. 15 other: ng/g

Remarks on result:

other: average value in liver based on reported graphs

Time point:

3 h

Dose:

0.42 mg/g

Parameter:

amount

Remarks:

in blood

Absorption:

ca. 5.3 other: ng/g

Remarks on result:

other: average value in blood based on reported graphs

Time point:

3 h

Dose:

0.42 mg/g

Parameter:

amount

Remarks:

in kidney

Absorption:

ca. 37 other: ng/g

Remarks on result:

other: average value in kidney based on reported graphs

Conclusions:

After 3-hour dermal exposure (depilated dorsal skin) of male F344 / N rats to a neutralized solution of sodium germanate (GeO2 dissolved in NaOH) in a hydrophilic ointment base (2 g ointment containing 0, 0.21 or 0.42 mg GeO2 / g ), the germanium content in whole blood, plasma, liver and kidney increased in a dose-dependent manner. The kidney content was about three times higher than that in the liver

Executive summary:

In this study the dermal absorption of neutralized GeO2 or germanate using male F344/N rats was investigated. Three groups of rats were treated with a 3-h topical application of hydrophilic ointment containing graded level of neutralized GeO2 (pH 7.4): 0, 0.21 and 0.42 mg GeO2/g. Germanium concentration in blood and tissues sampled from rats after topical application of inorganic germanium was measured by inductively coupled plasma-mass spectrometry. Animals topically applied 0.42 mg GeO2/g ointment had significantly higher germanium concentrations in plasma, liver, and kidney than those of rats that received no topical germanium. The results indicate that skin is permeable to inorganic germanium ion or germanate and recurrent exposure of germanium compounds may pose a potential health hazard.

Description of key information

In vitro studies have evaluated the dissolution rates of germanium dioxide. Data on the bioaccessibility of germanium dioxide in biological fluid (gastric medium pH 1.5) as a surrogate for bioavailability are reported within section 7.1.1 of IUCLID (Brouwers et al, ECTX, 2015). Gastric medium mimics the release of Ge from GeO2 after oral exposure.

For Germanium and its compounds, systemic toxicity is attributed to the germanium ion and differences in toxicity are principally linked to bioavailability. The bioelution data (for details see IUCLID section 7.1.1) are summarized below and have been incorporated into read-across assessments for Ge and Ge compounds. Further details related to the specific endpoints for which read-across approach was used, is summarized in section 13 of IUCLID (read across justification report).

Table- Bio-elution data on germanium and germanium compounds (germanium dioxide) measured in gastric fluids

Test Substance	Bioaccessibility in Gastric fluid (2 hours, loading 0.2g/L) as (% In released of total In-content)	Reference
GeO2	23.3	Brouwers T, 2015
Ge	5.83	Brouwers T, 2015

Animal studies:

Absorption, Distribution, Excretion:

Oral:

The study of Rosenfeld (1954) on rats after gavage to GeO2, demonstrates that germanium is rapidly absorbed after oral administration (73.6% in 4 hours; 96.4% in 8 hours).

When absorbed following oral administration, germanium is transported unbound by plasma proteins and is rapidly eliminated from the blood stream.

The biological half-life of germanium is relatively short, on the order of 1 -2 days in the liver and whole body and 4.5 days in the kidneys of rats (Rosenfeld, 1954).

Lin et al (1999) reported the kinetics of GeO2 in male Wistar rats after the oral administration of a single dose (100mg/kg) and found that maximal mean serum concentration was achieved in 0.7 hour and the mean elimination half-time was 2.3 hours. Lin et al, also conducted a multiple dose for 4 weeks and found highest concentrations of Ge in peripheral nerves and kidneys.

Inhalation:

The rate of clearance of deposited elemental germanium particles (mean size 1.7 µm) from the lungs of rats was found to be exponential (52% in 24 hours, 82% at 7th day after exposure). Radiochemical examination of the tissues showed that part of the material entered the circulation and reappeared in the kidney and liver 1 hour after exposure. The clearance of germanium dioxide particles (mean size 0.4 µm) was more rapid than that of elemental Ge particles (79% within 24 hours and nearly 100% at 4th day) (Dudley, 1953)

Dermal:

After 3-hour dermal exposure (depilated dorsal skin) of male F344/N rats to a neutralized solution of sodium germanate (GeO2 dissolved in NaOH) in a hydrophilic ointment base (2g ointment containing 0, 0.21 or 0.42 mg GeO2/g) the germanium content in whole blood, plasma, liver and kidney increased in a dose-dependent manner. The Ge content in the kidney was about three times higher than that in the liver (Yokoi et al, 2008). The results indicate that skin is permeable to inorganic germanium ion or germanate.

Human information:

Inhalation:

Roels and Buchet (2001) collected urine samples at the beginning and at the end of the day shift from workers occupationally exposed to Ge or GeO2 by inhalation. The urinary elimination rate of germanium was studied in seven workers, and the urinary elimination rates (half-times) ranged from 8.2 -18.1 hours. The study did not allow discrimination between the germanium species to which the workers were exposed but it showed fast urinary urinary elimination kinetics for inhalation exposure to dust of metallic Ge and GeO2.

References (in extra to study records):

- Dudley HC 1953: Pharmacological studies of radiogermanium (Ge71). II. Inhalation of dusts, AMA Arch Ind Hyg Occup Med. 8(6): 528 -530

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

73.6