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Lookup NU author(s): Dr Philippa Holder
This is the authors' accepted manuscript of an article that has been published in its final definitive form by National Academy of Sciences, 2018.
For re-use rights please refer to the publisher's terms and conditions.
© 2018 National Academy of Sciences. All rights reserved. Mass mortalities of honey bees occurred in France in the 1990s coincident with the introduction of two agricultural insecticides, imidacloprid and fipronil. Imidacloprid, a neonicotinoid, was widely blamed, but the differential potency of imidacloprid and fipronil has been unclear because of uncertainty over their capacity to bioaccumulate during sustained exposure to trace dietary residues and, thereby, cause time-reinforced toxicity (TRT). We experimentally quantified the toxicity of fipronil and imidacloprid to honey bees and incorporated the observed mortality rates into a demographic simulation of a honey bee colony in an environmentally realistic scenario. Additionally, we evaluated two bioassays from new international guidance for agrochemical regulation, which aim to detect TRT. Finally, we used analytical chemistry (GC-MS) to test for bioaccumulation of fipronil. We found in demographic simulations that only fipronil produced mass mortality in honey bees. In the bioassays, only fipronil caused TRT. GC-MS analysis revealed that virtually all of the fipronil ingested by a honey bee in a single meal was present 6 d later, which suggests that bioaccumulation is the basis of TRT in sustained dietary exposures. We therefore postulate that fipronil, not imidacloprid, caused the mass mortalities of honey bees in France during the 1990s because it is lethal to honey bees in even trace doses due to its capacity to bioaccumulate and generate TRT. Our results provide evidence that recently proposed laboratory bioassays can discriminate harmful bioaccumulative substances and, thereby, address evident shortcomings in a regulatory system that had formerly approved fipronil for agricultural use.
Author(s): Holder PJ, Jones A, Tyler CR, Cresswell JE
Publication type: Article
Publication status: Published
Journal: Proceedings of the National Academy of Sciences of the United States of America
Print publication date: 18/12/2018
Online publication date: 03/12/2018
Acceptance date: 05/11/2018
Date deposited: 07/01/2019
ISSN (print): 0027-8424
ISSN (electronic): 1091-6490
Publisher: National Academy of Sciences
PubMed id: 30509996
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