Selected neonicotinoids and associated risk for aquatic organisms

Abstract

Neonicotinoids are one of the newest groups of systemic pesticides, effective on a wide range of invertebrate pests. The success of neonicotinoids can be assessed according to the amount used, for example, in the Czech Republic, which now accounts for 1/3 of the insecticide market. The European Union (EU) has a relatively interesting attitude towards neonicotinoids. Three neonicotinoid substances (imidacloprid, clothianidin and thiamethoxam) were severely restricted in 2013. In 2019, imidacloprid and clothianidin were banned, while thiamethoxam and thiacloprid were banned in 2020. In 2022, another substance, sulfoxaflor, was banned. Therefore, only two neonicotinoid substances (acetamiprid and flupyradifurone) are approved for outdoor use in the EU. Neonicotinoids enter aquatic ecosystems in many ways. In European rivers, neonicotinoids usually occur in nanograms per litre. Due to the low toxicity of neonicotinoids to standard test species, they were not expected to significantly impact the aquatic ecosystem until later studies showed that aquatic invertebrates, especially insects, are much more sensitive to neonicotinoids. In addition to the lethal effects, many studies point to sublethal impacts -reduced reproductive capacity, initiation of downstream drift of organisms, reduced ability to eat, or a change in feeding strategies. Neonicotinoids can affect individuals, populations, and entire ecosystems.

Those That Remain Caught in the “Organic Matter Trap”: Sorption/Desorption Study for Levelling the Fate of Selected Neonicotinoids

“…Modern farmers can thus get caught on the “pesticide treadmill”, being forced to continuously and in increasing concentrations apply neonicotinoids with augmented toxicities [ 35 ]. Assessing both wildlife and human exposure risk from neonicotinoids requires comprehensive data collection about their fate, behavior, and ecotoxicological effects, but these data are either insufficient or of insufficient quality [ 30 , 36 ].…”

“…Only a proportion of active neonicotinoid substance applied is taken up by a plant, and in variable amounts (from 1.6 to 20%) [ 14 ], leaving residues that may undergo migration in soil (to other environmental media or non-target organisms), degradation (abiotic or biotic), or sorption/desorption processes, in which insecticide molecules become associated with the soil solid phase and retained in the soil matrix [ 37 ]. In fact, neonicotinoids are frequently detected in surface and groundwater across the world at average concentrations in surface water of tens to hundreds ng/L [ 10 , 36 , 37 , 38 ], and some of them occur in a variety of surface water at concentrations above the EU environmental quality standards of 0.1 μg/L [ 39 ]. Moreover, neonicotinoids are not readily biodegradable by soil microbial activity [ 38 , 40 ] and can persist in soils for months to years [ 41 ].…”