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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009-01-28 to 2009-06-01
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
GLP in-vitro bioaccessability study performed according to the "Draft Guidance for RIP 3.6: Bioavailability and Read-Across for Metals and Minerals".
Cross-reference
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009
Report Date:
2009

Materials and methods

Objective of study:
absorption
Test guideline
Qualifier:
according to
Guideline:
other: Draft Guidance for RIP 3.6: Bioavailability and Read-Across for Metals and Minerals
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Tungsten Carbide
- Substance type: Pure active substance
- Physical state: Solid, Gray powder
- Analytical purity: 100 %
- Purity test date: 2006-10-10
- Storage condition of test material: Store dry and away from powerful ignition sources
Radiolabelling:
no

Test animals

Species:
other: Human simulated fluids
Strain:
not specified
Sex:
not specified

Administration / exposure

Route of administration:
other: In vitro study
Details on exposure:
Preparation of Testing Fluids: The simulated fluids used in this study were gastric, lung alveolar, lung interstitial, lysosomal and artificial sweat. All salts and reagents used for the simulated fluid preparation were obtained from Sigma-Aldrich (St. Louis, MO).

Extraction Experiments: Extractions of the test substances in the simulated fluids were performed at pre-set time periods (up to 72 hours) while protected from light, using 0.1 g of sample in 50 ml of simulated fluid, at 37 C and with continuous shaking (for all fluids except sweat, for which only initial shaking was performed). The experiments were carried out as follows:
- Simulated Gastric Fluid: The reactions were sampled for the determination of tungsten at 5 hours.
- Simulated Interstitial, Alveolar and Lysosomal Fluids: 5% CO2 in nitrogen was bubbled into solution at a rate of 50 ml/min. The reactions were sampled for the determination of tungsten at 2, 5, 24, and 72 hours.
- Simulated Sweat: The reactions were sampled for the determination of tungsten after 12 hours. No shaking was performed after the initial set up.

Sample Preparation: The simulated fluid extract samples were filtered immediately after sampling using 50 ml centrifuge tubes equipped with 0.45 microns PVDF filters (Grace Alltech, Deerfield, IL). The filtrates were stored in plastic bottles at 35 C until analysis.

The extracts were then analyzed for tungsten by inductively coupled plasma-mass spectrometry (ICP-MS).
Duration and frequency of treatment / exposure:
Single application of tungsten with fluids. Simulated Gastric Fluid was sampled for the determination of tungsten at 5 hours. Simulated Interstitial, Alveolar and Lysosomal Fluids were sampled for the determination of tungsten at 2, 5, 24, and 72 hours. Simulated Sweat was sampled for the determination of tungsten after 12 hours.
Doses / concentrations
Remarks:
Doses / Concentrations:
0.1 g of test substance in 50 mL of simulated fluid
Control animals:
no
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Simulated gastric fluid, Simulated interstititial fluid, Simulated alveolar fluid, Simulated lysosomal fluid and Simulated sweat
- Time and frequency of sampling: Simulated gastric fluid sampled at 5 hours, Simulated interstititial fluid sampled at 2, 5, 24, and 72 hours, Simulated alveolar fluid sampled at 2, 5, 24, and 72 hours, Simulated lysosomal fluid sampled at 2, 5, 24, and 72 hours and Simulated sweat sampled after 12 hours.

Sample analysis: Samples were diluted (if necessary), spiked with an internal standard [bismuth (Bi) at 1,000 pg/mL, prepared from dilution of a 1,000 ug/mL Certified Standard; Ultra Scientific, North Kingston, RI and analyzed directly on a Perkin Elmer Elan DRC II ICP-MS equipped with a dynamic reaction cell (DRC) and PerkinElmer AS-93 Plus autosampler instrument, according to methods established at IITRI for this study. A standard curve (prepared from dilutions of a 10,000 5%HNO3/6% HF; inorganic Ventures, Lakewood, NJ] was analyzed along with samples on each day of analysis. Instruments calibrators were prepared by diluting Certified Standard with 0.5% nitric acid to concentrations of approximately 200; 400; 800; 1,600; 3,200; 6,400; 13,000; and 25,000 pg/mL.
Statistics:
Calibration curves, regression coefficients and r-squared values were calculated using PerkinElmer ICP-MS software and Microsoft Excel software. Concentration values of tungsten in the study samples were calculated from linear regression coefficients derived from calibration standards that bracketed the expected concentration levels of tungsten in the study samples.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Transfer into organs
Transfer type:
other: not applicable as it is an in vitro study
Toxicokinetic parameters
Toxicokinetic parameters:
other: not applicable as it is an in vitro study

Metabolite characterisation studies

Metabolites identified:
no

Bioaccessibility

Bioaccessibility testing results:
The fluid extracts were diluted 1:250 to 1:2500 for analysis. The average amount of tungsten found in the extracts was in the 0.019 to 0.48% range. The maximum solubility was determined at 72 hours for the simulated alveolar and lysosomal fluids (0.48 and 0.41%, respectively). Percent relative standard deviations (%RSDs) ranged from 2 to 74%.

Gastric Fluid: The percent of available tungsten in simulated gastric fluid sampled at 5 hours was 0.035 +/- 0.00071% (2.0 % relative standard deviation).
Sweat Fluid: The percent of available tungsten in simulated sweat fluid sampled at 12 hours was 0.076 +/-0.0030 % (4.0% relative standard deviation).
Alveolar Fluid: The percent of available tungsten in simulated alveolar fluid sampled at 2, 5, 24, and 72 hours was 0.019 +/- 0.0022%, 0.033 +/- 0.0012%, 0.089 +/- 0.0070%, and 0.48 +/-0.057 %, respectively; with percent relative standard deviations of 12, 3.7, 7.9, and 12 %RSD, respectively.
Lysosomal Fluid: The percent of available tungsten in simulated lysosomal fluid sampled at 2, 5, 24, and 72 hours was 0.078 +/- 0.047%, 0.092 +/- 0.059%, 0.20 +/- 0.15%, and 0.41 +/- 0.28 %, respectively with percent relative standard deviations of 60, 64, 74, and 68 %RSD, respectively.
Interstitial Fluid: The percent of available tungsten in simulated interstitial fluid sampled at 2, 5, 24, and 72 hours was 0.045 +/- 0.020%, 0.037 +/- 0.0089%, 0.065 +/- 0.010%, and 0.13 +/- 0.053 %, respectively with percent relative standard deviations of 44, 24, 15, and 41 %RSD, respectively.

Applicant's summary and conclusion

Conclusions:
The average amount of tungsten found in the extracts was in the 0.019 to 0.48% range. The maximum solubility was determined at 72 hours for the simulated alveolar and lysosomal fluids (0.48 and 0.41%, respectively).

The percent of available tungsten in simulated gastric fluid sampled at 5 hours was 0.035 +/- 0.0071% (2.0 % relative standard deviation). The percent of available tungsten in simulated sweat fluid sampled at 12 hours was 0.076 +/-0.0030 % (4.0% relative standard deviation). The percent of available tungsten in simulated alveolar fluid sampled at 2, 5, 24, and 72 hours was 0.019 +/- 0.0022%, 0.033 +/- 0.0012%, 0.089 +/- 0.0070%, and 0.48 +/-0.057 %, respectively; with percent relative standard deviations of 12, 3.7, 7.9, and 12 %RSD, respectively. The percent of available tungsten in simulated lysosomal fluid sampled at 2, 5, 24, and 72 hours was 0.078 +/- 0.047%, 0.092 +/- 0.059%, 0.20 +/- 0.15%, and 0.41 +/- 0.28 %, respectively with percent relative standard deviations of 60, 64, 74, and 68 %RSD, respectively. The percent of available tungsten in simulated interstitial fluid sampled at 2, 5, 24, and 72 hours was 0.045 +/- 0.020%, 0.037 +/- 0.0089%, 0.065 +/- 0.010%, and 0.13 +/- 0.053 %, respectively with percent relative standard deviations of 44, 24, 15, and 41 %RSD, respectively. Based on the results, the bioavailability of tungsten carbide would be expected to be low for the oral, dermal, and inhalation routes of administration.