Toxic Mixtures in Time—The Sequence Makes the Poison

Roman Ashauer; Isabel O’Connor; Beate I. Escher

doi:10.1021/acs.est.6b06163

Toxic Mixtures in Time—The Sequence Makes the Poison

Roman Ashauer, Isabel O’Connor, Beate I. Escher

Environment and Geography

Research output: Contribution to journal › Article › peer-review

Abstract

“The dose makes the poison”. This principle assumes that once a chemical is cleared out of the organism (toxicokinetic recovery), it no longer has any effect. However, it overlooks the other process of re-establishing homeostasis, toxicodynamic recovery, which can be fast or slow depending on the chemical. Therefore, when organisms are exposed to two toxicants in sequence, the toxicity can differ if their order is reversed. We test this hypothesis with the freshwater crustacean Gammarus pulex and four toxicants that act on different targets (diazinon, propiconazole, 4,6-dinitro-o-cresol, 4-nitrobenzyl chloride). We found clearly different toxicity when the exposure order of two toxicants was reversed, while maintaining the same dose. Slow toxicodynamic recovery caused carry-over toxicity in subsequent exposures, thereby resulting in a sequence effect–but only when toxicodynamic recovery was slow relative to the interval between exposures. This suggests that carry-over toxicity is a useful proxy for organism fitness and that risk assessment methods should be revised as they currently could underestimate risk. We provide the first evidence that carry-over toxicity occurs among chemicals acting on different targets and when exposure is several days apart. It is therefore not only the dose that makes the poison but also the exposure sequence.

Original language	English
Pages (from-to)	3084-3092
Number of pages	9
Journal	Environmental Science and Technology
Volume	51
Issue number	5
DOIs	https://doi.org/10.1021/acs.est.6b06163
Publication status	Published - 8 Feb 2017

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ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

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10.1021/acs.est.6b06163

51 Toxic mixtures in time - the sequence makes the poison
ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
Final published version, 1.17 MBLicence: Other

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Toxic Mixtures in Time—The Sequence Makes the Poison

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