Any of a class of synthetic pesticides based on the chemical structure of nicotine. They were introduced in the early 1990s for use as insecticides and have relatively low toxicity to humans and other mammals compared to alternatives such as organophosphates. They act by binding irreversibly to nicotinic acetylcholine receptors in the insect’s central nervous system, causing paralysis and death. Various neonicotinoid chemicals are used in horticultural, agricultural, and garden pesticides. Since the mid-2000s there has been growing evidence that these chemicals have harmful effects on pollinating insects, particularly bumblebees and honey bees, and may persist in the soil and vegetation adjacent to treated areas. In 2013 the EU introduced a temporary ban on the use of thiamethoxam, clothianidin, and imidacloprid in flowering crops such as oilseed rape and sunflowers on which bees feed, which remained in place as of 2018.