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Oral bioaccessibility testing and read-across hazard assessment of nickel compounds.

Regulatory toxicology and pharmacology : RTP (2012-03-01)
Rayetta G Henderson, Danielle Cappellini, Steven K Seilkop, Hudson K Bates, Adriana R Oller
ABSTRACT

In vitro metal ion bioaccessibility, as a measure of bioavailability, can be used to read-across toxicity information from data-rich, source substances to data-poor, target substances. To meet the data requirements for oral systemic toxicity endpoints under the REACH Regulation in Europe, 12 nickel substances underwent bioaccessibility testing in stomach and intestinal fluids. A read-across paradigm was developed based on the correlation between gastric bioaccessibility and in vivo acute oral toxicity. The oral LD₅₀ values were well predicted by nickel release (R² = 0.91). Samples releasing <48% available nickel (mgNi released/mg available Ni × 100) are predicted to have an LD₅₀ > 2000 mg/kg; while samples releasing > 76% available nickel are expected to have an LD₅₀ between 300 and 2000 mg/kg. The hazard classifications (European Regulation on Classification, Labelling and Packaging of Chemical Substances and Mixtures) for all oral systemic endpoints were evaluated based on read-across from three source nickel compounds (sulfate, subsulfide, oxide). Samples releasing < 48% available nickel were read-across from nickel oxides and subsulfide. Samples releasing > 76% Ni were read-across from nickel sulfate. This assessment suggests that nickel chloride and dihydroxide should be less stringently classified and nickel sulfamate should receive a more stringent classification for oral systemic endpoints than currently assigned.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Nickel(II) chloride, 98%
Sigma-Aldrich
Nickel(II) chloride hexahydrate, 99.9% trace metals basis
Sigma-Aldrich
Nickel(II) sulfate hexahydrate, ACS reagent, ≥98%
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Nickel(II) chloride hexahydrate, ReagentPlus®
Sigma-Aldrich
Nickel(II) sulfate, anhydrous, 99.99% trace metals basis
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Nickel(II) sulfate hexahydrate, ReagentPlus®, powder or crystals
Sigma-Aldrich
Nickel(II) chloride, anhydrous, powder, 99.99% trace metals basis
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Nickel(II) chloride hexahydrate, BioReagent, suitable for cell culture
Supelco
Nickel(II) sulfate hexahydrate, ≥99.99% trace metals basis
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Nickel(II) sulfate heptahydrate, purum p.a., crystallized, ≥99.0% (KT)
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Nickel(II) chloride hexahydrate, puriss. p.a., ≥98%
Sigma-Aldrich
Nickel(II) chloride hexahydrate, 99.999% trace metals basis
Sigma-Aldrich
Nickel(II) sulfate heptahydrate, 99.999% trace metals basis
Sigma-Aldrich
Nickel(II) chloride hydrate, 99.95% trace metals basis
Sigma-Aldrich
Nickel(II) sulfate hexa-/ heptahydrate, for nickel plating, DIN 50970 H, ≥20.6% Ni and Co basis