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Nitrogen Cycle Bacteria in Agricultural Soils
Published in Vivek Kumar, Rhizomicrobiome Dynamics in Bioremediation, 2021
Guillermo Bravo, Paulina Vega-Celedón, Constanza Macaya, Ingrid-Nicole Vasconez, Michael Seeger
Neonicotinoids Neonicotinoids are the most widely used insecticides despite their toxicity (Skandrani et al. 2006). In 2010, these systemic insecticides’ production was estimated to be 20,000 tonnes, with presence in more than 120 countries (CCM International 2011, Simon-Delso et al. 2015). These compounds disrupt the neuronal transmission in the central nervous system of invertebrates by mimicking the action of neurotransmitters, binding with a high specific affinity to the acetylcholine receptor (nAChR) of insects (Stygar et al. 2013). Important crop pests, such as sap-feeding insects Aphidae (aphids), and Chrysomelidae (among others, western corn rootworm) can be controlled by neonicotinoids (Tomizawa and Casida 2005, Elbert et al. 2008). Regarding the chemical structure, the main commercial neonicotinoids contained three structural components: (i) a N-heterocyclyl-methyl moiety, (ii) a heterocyclic or acyclic spacer, and (iii) a N-nitroimine, nitromethylene, or N-cyanoimine pharmacophore (Casida 2011). These compounds are translocated easily into the xylem of plants and exhibit high translaminar movement (Canadian Council of Ministers of the Environment 2007). The first-generation neonicotinoids, imidacloprid (IMI) and thiacloprid (THI), that belong to the chloronicotinyl subclass, and thiamethoxam (TMX), a second-generation neonicotinoid that belongs to the thianicotinyl subclass, are the most used insecticides in the world (Jeschke et al. 2011, Tomizawa and Casida 2010, Zhou et al. 2013, Ge et al. 2014).
Potency matters: Impacts of embryonic exposure to nAChR agonists thiamethoxam and nicotine on hatching success, growth, and neurobehavior in larval zebrafish
Published in Journal of Toxicology and Environmental Health, Part A, 2022
Shayla Victoria, Megan Hein, Elisabeth Harrahy, Tisha C King-Heiden
Thiamethoxam (TM) is one of the more commonly used neonicotinoid pesticides worldwide, especially in the Midwest region of the United States (WI DATCP 2018; Hladik, Kolpin, and Kuivila 2014; Stephenson and Solomon 2017). These ubiquitous environmental contaminants are of emerging concern as they are found in both drinking water and surface waters of rivers and streams (WI DATCP 2018; Hladik and Kolpin 2016; Hladik, Kolpin, and Kuivila 2014; Stephenson and Solomon 2017). Neurobehavioral functions of zebrafish are altered following embryonic and larval exposure to the neonicotinoid imidacloprid (Crosby et al. 2015), but less is known regarding the potential neurotoxicity of TM in fish. Liu et al. (2018) noted that exposure to 100 µg TM/l altered locomotor activity in zebrafish (Danio rerio), while Zhu et al. (2019) found that TM concentrations as low as 0.5 µg/L induced changes to tissues and gene expression in the HPG (hypothalamic-pituitary-gonad) and HPT (hypothalamic-pituitary-thyroid) axes in adult Chinese rare minnows (Gobiocypris rarus). Fathead minnow larvae (Pimephales promelas) experience decreased survival rates, increased embryonic motor activity, and altered predator escape responses at early life stages following chronic exposure to environmentally relevant concentrations of TM (Victoria et al. 2022). While the US EPA has not finalized a human health risk assessment for TM, recent reviews of epidemiological studies suggest that chronic exposure to neonicotinoid pesticides is also associated with adverse developmental and neurological outcomes in humans (Cimino et al. 2017; Thompson et al. 2020). It is of interest that neurobehavioral abnormalities were a more sensitive indicator than immunotoxicity following sublethal effects of oral exposure to imidacloprid in domestic chickens (Gallus gallus domesticus) (Franzen-Klein et al. 2020).
Treatment of effluent containing thiamethoxam and efficiency evaluation of toxicity reduction
Published in Environmental Technology, 2021
Clarice Fieira, Eduardo Pavan Batistella, Jose Vitor Abilhoa Vincoski, Marcos Paulo Scaglia Rosa, Juan Carlos Pokrywiecki, Eduardo Michel Vieira Gomes, Ana Paula de Oliveira, Ticiane Sauer Pokrywiecki, Elisângela Düsman
The use of pesticides in seed treatments is a widely employed technique that aims to prevent productivity losses due to insect attacks on seeds and seedlings and thus protect the genetic potential of the grain [1,2]. Several active principles are used in seed treatments, including thiamethoxam, which is an effective insecticide for chewing and sucking insects. It has a powerful systemic action because it is slowly metabolized by plants and remains active for several weeks after use [3,4].