In risk assessment, metals are evaluated conservatively, as if they exist in the environment as a pure metal or a specific chemical, such as a soluble salt; however, bioavailability and toxicity are well recognized to vary relative to the solubility of the metal ion in biological fluids (e.g., gastric fluid, lung fluid). In many matrices, including alloys and slags and mine tailings, metal ions are not readily released into biological fluids and are determined to have limited bioaccessibility and bioavailability. In vitro bioaccessibility (IVBA) is a test method based on simulated biological fluids, that is used to estimate in vivo conditions. It has been used by US regulators for risk assessment and is also under consideration by the European Chemicals Agency (ECHA) for read-across.
ToxStrategies’ Relevant Published Work:
- Oral bioaccessibility testing and in vivo validation for read-across of nickel compounds.
- Interlaboratory validation study of IVBA test methods for various metals and matrices for gastric, dermal, and inhalation pathways.
- In vivo relative bioavailability study for nickel and cobalt in dust and soil using a juvenile swine model.
ToxStrategies’ Test Method Development:
- ToxStrategies participated in the Bioelution Working Group of the EURL ECVAM (European Union Reference Laboratory for Alternatives to Animal Testing) Scientific Advisory Committee in 2019, to review the scientific validity of a proposed bioelution test method to assess the relative IVBA of metals and metalloids in inorganic metal compounds and materials (published in 2020).
- ToxStrategies is participating in the OECD panel of international experts from Europe, the United States, Canada, and Japan to develop a new Test Guideline to determine relative metal release using a simulated gastric fluid.
|Source||Metals Evaluated||Environmental Media1||IVBA Exposure Pathway Evaluated|
|Titanium & steel forge||CrVI, total Cr, Co, Mo, Ni, V||Soil and dust||Oral|
|Specialty steel foundry||As, CrVI, total Cr, Co, Ni||Baghouse dust, soil||Oral, Inhalation|
|Steel mill||As, Cd, CrVI, total Cr, Co, Pb, Mn, Ni||EAF and LF slags, furnace dust||Oral, Inhalation|
|Specialty steel forge||Co, Ni||Soil and dust||Oral, Inhalation|
|Steel slag processors||Al, Sb, As, Ba, Be, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Hg, Mo, Ni, P, Se, Si, Ag, T, Sn, V, Zn||EAF, BOF, and BF slags||Oral|
|Steel slag processor||CrVI, total Cr, Mn||Aged and fresh EAF slag mixed with soil||Oral|
1 EAF = electric arc furnace, LF = ladle furnace, BOF = basic oxygen furnace, BF = blast furnace