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Henderson, R. G., Verougstraete, V., Anderson, K., Arbildua, J. J., Brock, T. O., Brouwers, T., et al. (2014). Inter-laboratory validation of bioaccessibility testing for metals. Regul. Toxicol. Pharmacol., 70(1), 170–181.
Abstract: Bioelution assays are fast, simple alternatives to in vivo testing. In this study, the intra- and inter-laboratory variability in bioaccessibility data generated by bioelution tests were evaluated in synthetic fluids relevant to oral, inhalation, and dermal exposure. Using one defined protocol, five laboratories measured metal release from cobalt oxide, cobalt powder, copper concentrate, Inconel alloy, leaded brass alloy, and nickel sulfate hexahydrate. Standard deviations of repeatability (S-r) and reproducibility (S-R) were used to evaluate the intra- and inter-laboratory variability, respectively. Examination of the s(R):s(r) ratios demonstrated that, while gastric and lysosomal fluids had reasonably good reproducibility, other fluids did not show as good concordance between laboratories. Relative standard deviation (RSD) analysis showed more favorable reproducibility outcomes for some data sets; overall results varied more between- than within-laboratories. RSD analysis of s(r) showed good within-laboratory variability for all conditions except some metals in interstitial fluid. In general, these findings indicate that absolute bioaccessibility results in some biological fluids may vary between different laboratories. However, for most applications, measures of relative bioaccessibility are needed, diminishing the requirement for high inter-laboratory reproducibility in absolute metal releases. The inter-laboratory exercise suggests that the degrees of freedom within the protocol need to be addressed. (C) 2014 Elsevier Inc. All rights reserved.
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Santore, R. C., Ryan, A. C., Kroglund, F., Rodriguez, P. H., Stubblefield, W. A., Cardwell, A. S., et al. (2018). Development and Application of a Biotic Ligand Model for Predicting the Chronic Toxicity of Dissolved and Precipitated Aluminum to Aquatic Organisms. Environ. Toxicol. Chem., 37(1), 70–79.
Abstract: Aluminum (Al) toxicity to aquatic organisms is strongly affected by water chemistry. Toxicity-modifying factors such as pH, dissolved organic carbon (DOC), hardness, and temperature have a large impact on the bioavailability and toxicity of Al to aquatic organisms. The importance of water chemistry on the bioavailability and toxicity of Al suggests that interactions between Al and chemical constituents in exposures to aquatic organisms can affect the form and reactivity of Al, thereby altering the extent to which it interacts with biological membranes. These types of interactions have previously been observed in the toxicity data for other metals, which have been well described by the biotic ligand model (BLM) framework. In BLM applications to other metals (including cadmium, cobalt, copper, lead, nickel, silver, and zinc), these interactions have focused on dissolved metal. A review of Al toxicity data shows that concentrations of Al that cause toxicity are frequently in excess of solubility limitations. Aluminum solubility is strongly pH dependent, with a solubility minimum near pH 6 and increasing at both lower and higher pH values. For the Al BLM, the mechanistic framework has been extended to consider toxicity resulting from a combination of dissolved and precipitated Al to recognize the solubility limitation. The resulting model can effectively predict toxicity to fish, invertebrates, and algae over a wide range of conditions. (C) 2017 SETAC
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Urrestarazu, P., Villavicencio, G., Opazo, M., Arbildua, J., Boreiko, C., Delbeke, K., et al. (2014). Migration protocol to estimate metal exposure from mouthing copper and tin alloy objects. Environ. Health, 13, 9 pp.
Abstract: Background: Low blood lead levels previously thought to pose no health risks may have an adverse impact on the cognitive development of children. This concern has given rise to new regulatory restrictions upon lead metal containing products intended for child use. However few reliable experimental testing methods to estimate exposure levels from these materials are available. Methods: The present work describes a migration test using a mimetic saliva fluid to estimate the chronic exposure of children to metals such as lead while mouthing metallic objects. The surrogate saliva medium was composed of: 150 mM NaCl, 0.16% porcine Mucin and 5 mM buffer MOPS, adjusted to pH 7.2. Alloys samples, in the form of polished metallic disc of known surface area, were subjected to an eight hours test. Results: Two whitemetal alloys Sn/Pb/Sb/Cu and three brass alloys Cu/Zn/Pb were tested using the saliva migration protocol. In the case of the whitemetal alloys, first order release kinetics resulting in the release of 0.03 and 0.51 μg lead/cm(2) after 8 hours of tests were observed, for lead contents of 0.05-0.07% and 5.5%, respectively. Brasses exhibited linear incremental release rates of 0.043, 0.175 and 0.243 μg lead/cm(2)h for lead contents of 0.1-0.2%, 1.7-2.2% and 3.1-3.5%, respectively. The linear regression analysis of lead release rates relative to Pb content in brasses yielded a slope of 0.08 μg lead/cm(2)h% Pb (r(2) = 0.92). Lead release rates were used to estimate the mean daily mouthing exposure of a child to lead, according to age-specific estimates of mouthing time behavior. Calculated daily intakes were used as oral inputs for the IEUBK toxicokinetic model, predicting only marginal changes in blood lead levels (0.2 μg lead/dL or less) for children aged 0.5 to 1 years old exposed to either class of alloy. Conclusions: The results of this study as a whole support the use of migration data of metal ions, rather than total metal content, to estimate health risk from exposure to metals and metal alloys substances in children.
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