The design of an environmentally relevant mixture of persistent organic pollutants for use in in vivo and in vitro studies

ABSTRACT

Amongst the substances listed as persistent organic pollutants (POP) under the Stockholm Convention on Persistent Organic Pollutants (SCPOP) are chlorinated, brominated, and fluorinated compounds. Most experimental studies investigating effects of POP employ single compounds. Studies focusing on effects of POP mixtures are limited, and often conducted using extracts from collected specimens. Confounding effects of unmeasured substances in such extracts may bias the estimates of presumed causal relationships being examined. The aim of this investigation was to design a model of an environmentally relevant mixture of POP for use in experimental studies, containing 29 different chlorinated, brominated, and perfluorinated compounds. POP listed under the SCPOP and reported to occur at the highest levels in Scandinavian food, blood, or breast milk prior to 2012 were selected, and two different mixtures representing varying exposure scenarios constructed. The in vivo mixture contained POP concentrations based upon human estimated daily intakes (EDIs), whereas the in vitro mixture was based upon levels in human blood. In addition to total in vitro mixture, 6 submixtures containing the same concentration of chlorinated + brominated, chlorinated + perfluorinated, brominated + perfluorinated, or chlorinated, brominated or perfluorinated compounds only were constructed. Using submixtures enables investigating the effect of adding or removing one or more chemical groups. Concentrations of compounds included in feed and in vitro mixtures were verified by chemical analysis. It is suggested that this method may be utilized to construct realistic mixtures of environmental contaminants for toxicity studies based upon the relative levels of POP to which individuals are exposed.

Acknowledgements

The authors acknowledge the Research Council of Norway for funding the project. We further wish to thank Anuschka Polder and Georg Becher for helpful advice when planning the design and preparation of the mixtures, and Nina Hårdnes Tremoen for participating in the initial part of the literature review. We also thank Per Ola Darnerud and Arvid Fromberg for providing additional information regarding their studies when contacted, acting as personal references, and for helpful discussions on levels of different compounds and their relevance for inclusion in the mixtures. We are also grateful for the help provided by Ellen Dahl during preparation of the mixtures, as well as Jan Lyche for willingness to help with analyses of chemical levels in the in vitro mixture and feed. Finally, we thank Christopher Friis Berntsen for critically reviewing and copyediting the document.

Declaration of interest

The authors declare that there are no conflicting interests.

Funding

All parts of this project were funded by the Research Council of Norway [grant numbers 204361/H10 and 213076/H10].

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Additional information

Funding

All parts of this project were funded by the Research Council of Norway [grant numbers 204361/H10 and 213076/H10].