. 2016 Dec 20;6:37655. doi: 10.1038/srep37655

Table 1. Rationale for chemical selection based on mode of action and current concerns about agrochemicals and trace pollutants in the environment.

Chemical	Primary use	Class	Mode of action	Background for selection
Dimethoate	Spray and topical insecticide	Organophosphate	Binds to and irreversibly inactivates acetylcholinesterase. Active ingredient is a serine protease that hydrolyses the neurotransmitter acetylcholine at the synaptic junction.	Used to control a range of pests and the OEC reference toxicant used in routine testing honeybees and other arthropod species)¹⁴. Potential for increased OP use as other pesticides are withdrawn from use
2,4-Dichlorophenoxyacetic acid	Herbicide	Synthetic auxin	Mimics plant growth hormone auxin	A synthetic auxin herbicide, widely used for control of broadleaf weeds
Clothianidin	Systemic insecticide	Chloro-nicotinyl	Binds to nicotinic acetylcholine receptors to trigger activation and nervous overstimulation	A neonicotinoid insecticide which is used as a systemic insecticide and seed dressing against a wide variety of agricultural pests
Tau-fluvalinate	Varroacide and pesticide on oilseed rape	Pyrethroid	Binds to voltage-gated sodium channels in order to depolarise nerves. Relatively low binding to receptor in bees	A synthetic pyrethroid insecticide used against agricultural pests and extensively for Varroa destructor mite control in bee hives (high probability of coexposure). This insecticide is considered relatively non-toxic to bees, but is reported as being highly persistent in bee hives⁵⁹ and has shown evidence of synergism when considering P450-mediated detoxification pathways⁴⁶
Propiconazole	Fungicide	Conazole	Sterol biosynthesis inhibition by blocking the cytochrome P450 14-alpha-demethylase	A sterol inhibiting and commonly used fungicide in rape from a class identified as a potential synergist when part of a co-exposure A sterol inhibiting broad spectrum fungicide from a class of fungicides that have been reported as a potential synergists with other chemicals (Cedergreen 2006)⁶⁰
Cadmium	Environmental contaminant	Heavy metal	Induces genomic instability through complex and multifactorial mechanisms.	A non-essential heavy metal that is a known widespread toxic environmental contaminant with long-term and diverse toxic effects.
Arsenic	Historic use as pesticide	Metalloid	Co-factor substitution in metalloproteins, oxidative stress effect on the structure and functions of plasma membranes and effects on macromolecules including genotoxicity.	Widespread non-essential metal contaminant in soils, water and dust especially in agricultural areas due to past pesticide use and its presence in trace amounts in phosphate fertiliser. Known to be highly toxic and affect the genome. Included in study to provide cross validation for other ecotoxicity tests.