Sorptive physiologically based extraction of contaminated solid matrices: incorporating silicone rod as absorption sink for hydrophobic organic contaminants

The oral bioaccessibility of soil contaminants is increasingly assessed with Physiologically Based Extraction Tests (PBETs) to fine tune human health risk assessment of contaminated land. In these tests the contaminant fraction that is desorbed into simulated digestive fluids is measured and classified as bioaccessible. However, this approach can lead to underestimations if the capacity of the fluids is insufficient to provide infinite bath conditions. To circumvent this artefact, we incorporated a silicone rod as an absorption sink into the PBET to continuously absorb mobilized contaminants and maintain the desorption gradient. Polycyclic aromatic hydrocarbons served as model contaminants and the colon extended PBET (CEPBET) as the extraction model. The inclusion of the silicone rod sink (1) increased the extraction capacity of the test by orders of magnitude, (2) ensured (near) infinite bath conditions and (3) allowed for simple back-extraction of PAHs for their quantification by GC-MS. The silicone rod provided fast enrichment when applied to the stomach and small intestine compartment, but was somewhat slower in the carbohydrate colon compartment. Finally, the sorptive-CEPBET was applied to wood soot and a kindergarten soil. The present article provides the basis for how an absorption sink can be integrated into PBET models

EURL ECVAM strategy for achieving 3Rs impact in the assessment of toxicokinetics and systemic toxicity

Information on human toxicokinetics plays an important role in the safety assessment of chemicals, even though there are few data requirements in the EU regulatory framework. While existing EU test methods and OECD test guidelines are mostly based on animal procedures, there are increasing opportunities to achieve a 3Rs impact in this area by exploiting modern developments. For example, whole-body toxicokinetic information can be obtained by using physiologically-based toxicokinetic (PBTK) models that integrate data generated by in vitro methods for absorption, distribution, metabolism and excretion (ADME). The development of an infrastructure providing access to such models and their underlying data needs to be accompanied by the establishment of standards for human in vitro ADME methods, the development of guidance on the development and application of such models and the creation of regulatory incentives. Taking these needs into account, this report describes the EURL ECVAM strategy to achieve a 3Rs impact in the area of toxicokinetics and systemic toxicity. The proposed activities are expected to lay the foundation for a risk assessment approach that is increasingly based on human data. Implementation of the strategy will rely on the coordinated efforts of multiple stakeholders.JRC.I.5-Systems Toxicolog

How to Determine the Environmental Exposure of PAHs Originating from Biochar

Biochars are obtained by pyrolyzing biomass materials and are increasingly used within the agricultural sector. Owing to the production process, biochars can contain polycyclic aromatic hydrocarbons (PAHs) in the high mg/kg range, which makes the determination of the environmental exposure of PAHs originating from biochars relevant. However, PAH sorption to biochar is characterized by very high (10⁴–10⁶ L/kg) or extreme distribution coefficients (<i>K</i>_D) (>10⁶ L/kg), which makes the determination of exposure scientifically and technically challenging. Cyclodextrin extractions, sorptive bioaccessibility extractions, Tenax extractions, contaminant traps, and equilibrium sampling were assessed and selected methods used for the determination of bioavailability parameters for PAHs in two model biochars. Results showed that: (1) the <i>K</i>_D values of typically 10⁶–10⁹ L/kg made the biochars often act as sinks, rather than sources, of PAHs. (2) Equilibrium sampling yielded freely dissolved concentrations (pg–ng/L range) that were below or near environmental background levels. (3) None of the methods were found to be suitable for the direct measurement of the readily desorbing fractions of PAHs (i.e., bioacessibility) in the two biochars. (4) The contaminant-trap method yielded desorption-resistant PAH fractions of typically 90–100%, implying bioaccessibility in the high μg/kg to low mg/kg range

Alternative methods for regulatory toxicology – a state-of-the-art review

This state-of-the art review is based on the final report of a project carried out by the European Commission’s Joint Research Centre (JRC) for the European Chemicals Agency (ECHA). The aim of the project was to review the state of the science of non-standard methods that are available for assessing the toxicological and ecotoxicological properties of chemicals. Non-standard methods refer to alternatives to animal experiments, such as in vitro tests and computational models, as well as animal methods that are not covered by current regulatory guidelines. This report therefore reviews the current scientific status of non-standard methods for a range of human health and ecotoxicological endpoints, and provides a commentary on the mechanistic basis and regulatory applicability of these methods. For completeness, and to provide context, currently accepted (standard) methods are also summarised. In particular, the following human health endpoints are covered: a) skin irritation and corrosion; b) serious eye damage and eye irritation; c) skin sensitisation; d) acute systemic toxicity; e) repeat dose toxicity; f) genotoxicity and mutagenicity; g) carcinogenicity; h) reproductive toxicity (including effects on development and fertility); i) endocrine disruption relevant to human health; and j) toxicokinetics. In relation to ecotoxicological endpoints, the report focuses on non-standard methods for acute and chronic fish toxicity. While specific reference is made to the information needs of REACH, the Biocidal Products Regulation and the Classification, Labelling and Packaging Regulation, this review is also expected to be informative in relation to the possible use of alternative and non-standard methods in other sectors, such as cosmetics and plant protection products.JRC.I.5-Systems Toxicolog

EURL ECVAM Status Report on the Development, Validation and Regulatory Acceptance of Alternative Methods and Approaches (2015)

The EURL ECVAM status report provides an update on the progress made in the development, validation and regulatory acceptance of alternative methods and approaches and their dissemination since the last report published in June 2014. It is informing on ongoing research and development activities, validation studies, peer reviews, recommendations, strategies and regulatory/international acceptance of alternative methods and approaches and dissemination activities. R&D activities within large European or International consortia continued in toxicity areas where 3Rs solutions are more difficult to find due to the underlying complexity of the area. On the other hand, toxicity areas where promising non-animal approaches have been developed, their validation and regulatory acceptance/international adoption could be progressed. Particular emphasis was given to the best and most intelligent combination and integration of these different non-animal approaches to ultimately obtain the required information without resorting to animal testing.JRC.I.5-Systems Toxicolog

Sorptive Bioaccessibility Extraction (SBE) of Soils: Combining a Mobilization Medium with an Absorption Sink

In principle, soil bioaccessibility extraction methods are simple dissolution experiments, where the fraction of compounds that is transferred to the extraction medium is measured and considered to be bioaccessible. For hydrophobic organic chemicals (HOCs) such techniques can lead to underestimation of bioaccessibility when the capacity of the extraction medium is insufficient to provide infinite sink conditions for the target compounds. A sorptive bioaccessibility extraction (SBE) method was thus developed and validated, which integrates the key processes of desorption from the matrix and subsequent consumption or depletion. Cyclodextrin was used as a diffusive carrier to enhance desorption from the matrix, while a silicone rod was used as a dominating sink that continuously absorbed the HOC molecules from the cyclodextrin solution. The silicone rod was then solvent extracted and the HOCs measured by GC-MS. For wood soot, the SBE method yielded PAH bioaccessibility estimates that were 3–24 times higher compared to a cyclodextrin extraction without a sink. The study demonstrated that the inclusion of an absorption sink into an established bioaccessibility extraction method (1) is rather simple, (2) can have a major impact on the obtained results, especially for the more hydrophobic compounds and (3) can simplify the analytics

Sorptive Physiologically Based Extraction of Contaminated Solid Matrices: Incorporating Silicone Rod As Absorption Sink for Hydrophobic Organic Contaminants

The oral bioaccessibility of soil contaminants is increasingly assessed with physiologically based extraction tests (PBETs): the contaminant fraction that is desorbed into simulated digestive fluids is measured and classified as bioaccessible. However, this approach can lead to underestimations if the capacity of the fluids is insufficient to provide infinite sink conditions. Desorption will then progressively decrease and finally stop when equilibrium between soil and medium is reached. To circumvent this artifact, we incorporated a silicone rod as an absorption sink into the PBET to continuously absorb mobilized contaminants and maintain the desorption gradient. Polycyclic aromatic hydrocarbons served as model contaminants and the colon extended PBET as the extraction model. The inclusion of the silicone rod sink (1) increased the extraction capacity of the test by orders of magnitude, (2) ensured near infinite sink conditions, and (3) allowed for simple back-extraction of PAHs for their quantification by GC-MS. The silicone rod provided fast enrichment when applied to the stomach and small intestine compartment, but was somewhat slower in the richer colon compartment. Finally, the sorptive-PBET was applied to wood soot and a kindergarten soil. The present article provides the basis for how an absorption sink can be integrated into PBET models