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Potential Applications of Clay-Based Therapy for the Reduction of Pesticide Exposures in Humans and Animals

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Potential Applications of Clay-Based Therapy for the Reduction of Pesticide Exposures in Humans and Animals applied sciences Article Potential Applications of Clay-Based Therapy for the Reduction of Pesticide Exposures in Humans and Animals Meichen Wang and Timothy D. Phillips * Veterinary Integrative Biosciences Department, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-979-845-6414 Received: 4 November 2019; Accepted: 4 December 2019; Published: 6 December 2019 Featured Application: Novel, clay-based sorbents, developed from montmorillonites that have been shown to be safe for human and animal consumption, can significantly decrease hazardous pesticide exposures when included in food, drinking water and feed. Abstract: The risk of pesticide exposure in humans and animals may be magnified following natural and man-made disasters such as hurricanes and floods that can result in mobilization and redistribution of contaminated sediments. To develop broad-acting sorbents for mixtures of diverse toxins, we have processed calcium and sodium montmorillonite clays with high concentrations of sulfuric acid. These acid-processed montmorillonite clays (APMs) have shown limited hydration and swelling in water, higher surface areas, and lower trace metal levels than the parent clays, prior to processing. Isothermal analyses have indicated that newly developed APMs are highly active sorbents, with significantly increased binding capacities for a wide range of pesticides, including pentachlorophenol (PCP), 2,4,6-trichlorophenol (2,4,6-TCP), lindane, diazinon, linuron, trifluralin and paraquat. The safety and protective effects of APMs, against pesticide design mixtures, were confirmed in a living organism (Hydra vulgaris). Further work is planned to confirm the safety of the APMs in long-term rodent studies. This is the first report of a sorbent material (other than carbon) with high binding efficacy for mixtures of these pesticides. Based on our results, APMs (and similar clays), may be able to decrease human and animal pesticide exposures during disasters and emergencies. Keywords: pesticides; acid activation; adsorption; isotherms; hydra; montmorillonite; clay; enterosorbent 1. Introduction More than 1 billion pounds of pesticides are used in the United States each year and nearly 6 billion pounds are used worldwide [1]. The use of pesticides is of major importance to agriculture, but their widespread occurrence and persistence in the environment can be hazardous to living organisms. It was reported that less than 1% of the total of applied pesticides reach the targets, so a high percentage of these chemicals may move off-target [2,3]. The residues of pesticides are frequently detected in various environmental matrixes, such as soil, water, air, and organism bodies [4]. Moreover, natural and man-made disasters (such as hurricanes and floods) can significantly mobilize these environmental contaminants, exposing humans and animals to contaminated soil and sediment and threatening the safety of municipal drinking water and food sources. Highly toxic and widely distributed pesticides that are on a watch list due to a potentially severe and/or cumulative risk to human health and/or the environment, or have been banned for use as Appl. Sci. 2019, 9, 5325; doi:10.3390/app9245325 www.mdpi.com/journal/applsci Appl. Sci. 2019, 9, 5325 2 of 15 suggested by the United Nations and the Food and Agriculture Organization [5,6], were chosen for this study. These include: the organochlorines: pentachlorophenol (PCP), 2,4,6-trichorophenol (2,4,6-TCP) and lindane;Appl. Sci. 2019 an, organophosphate:9, x FOR PEER REVIEW diazinon; a urea-type pesticide: linuron; a dinitroaniline:2 trifluralin; of 15 and a bipyridyl pesticide: paraquat [7]. this study. These include: the organochlorines: pentachlorophenol (PCP), 2,4,6-trichorophenol (2,4,6- PCPTCP) isand widespread, lindane; an persistentorganophosphate: in the environmentdiazinon; a urea-type and highly pesticide: toxic linuron; to humans a dinitroaniline: and animals [8]. It hastrifluralin; been classified and a bipyridyl as a possible pesticide: carcinogen paraquat [7]. by the International Agency for Research on Cancer (IARC) [9PCP]. PCP is widespread, has been persistent banned for in the purchase environment and useand byhighly the toxic general to humans public, and but animals it is still [8]. used frequentlyIt has been for industrial classified as applications. a possible carcinogen 2,4,6-TCP by has the beenInternational commonly Agency used for as Research a pesticide on Cancer and wood preservative(IARC) [9]. [10 PCP]. It hashas beenbeen reportedbanned for that purchase exposure andto use 2,4,6-TCP by the general may increase public, but the it risk is still of behavioral used impairmentfrequently in childrenfor industrial and applications. carcinogenicity 2,4,6-TCP in humans. has been These commonly chlorophenol used as compoundsa pesticide and are wood persistent in thepreservative environment [10]. andIt has can been be reported commonly that exposure detected to in2,4,6- rivers,TCP may ponds increase and the soils risk [11 of]. behavioral Lindane is a impairment in children and carcinogenicity in humans. These chlorophenol compounds are hexachlorocyclohexane that is widely used to treat scabies and pediculosis. It is persistent and persistent in the environment and can be commonly detected in rivers, ponds and soils [11]. Lindane undegradable, and thus tends to bioaccumulate in the food chain [12]. is a hexachlorocyclohexane that is widely used to treat scabies and pediculosis. It is persistent and Diazinonundegradable, is an and organophosphorus thus tends to bioaccumulate insecticide, in the which food chain has been [12]. effectively used throughout the world withDiazinon applications is an organophosphorus in agriculture and insecticide, horticulture which for has controlling been effectively insects. used Its toxicity throughout is due the to the inhibitionworld ofwith the applications enzyme acetylcholine in agriculture esterase and horticulture [13]. for controlling insects. Its toxicity is due to Linuronthe inhibition is a phenylurea of the enzyme herbicide acetylcholine usedwidely esterase to [13]. selectively control weeds and grasses by inhibiting photosynthesis.Linuron It is has a phenylurea been shown herbicide to act as used an androgen widely to receptor selectively ligand control that weeds can competitively and grasses by inhibit the bindinginhibiting of androgensphotosynthesis. and It produce has been reproductive shown to act malformations as an androgen [14, 15receptor]. ligand that can Trifluralincompetitively is inhibit dinitroaniline the binding herbicide of androgens which and controls produce areproductive wide variety malformations of grasses [14,15]. and broadleaf Trifluralin is dinitroaniline herbicide which controls a wide variety of grasses and broadleaf weeds by interrupting mitosis, controlling weeds as they germinate. It is one of the most widely used weeds by interrupting mitosis, controlling weeds as they germinate. It is one of the most widely used herbicides [16]. Trifluralin has been banned in the European Union since 2008, primarily due to its herbicides [16]. Trifluralin has been banned in the European Union since 2008, primarily due to its highhigh toxicity toxicity to aquatic to aquatic life life [17 [17].]. ParaquatParaquat is one is one of theof the most most widely widely used used herbicidesherbicides due due to to its its rapid, rapid, contact-dependent contact-dependent killing killing of of weedsweeds and and plants plants [18 ].[18]. It isIt theis the leading leading cause cause ofof deathdeath from from pesticide pesticide self-poisoning self-poisoning and and murder. murder. ExposureExposure to theseto these pesticides pesticides can can stimulate stimulate lipid peroxidation, peroxidation, paralyze paralyze the therespiratory respiratory system, system, causecause endocrine endocrine disruption disruption and aandffect affect the nervous the nervou ands reproductive and reproductive system, system, etc. [ 19etc.–21 [19–21].]. The molecularThe modelsmolecular of each models pesticide, of each derived pesticide, from derived a computational from a computational quantum quantum mechanical mechanical AM1 methodAM1 in HyperChem,method in are HyperChem, shown in are Figure shown1. in Figure 1. (a) (b) (c) (d) (e) (f) (g) FigureFigure 1. Molecular 1. Molecular models models of:of: ( a)) pentachlorophenol pentachlorophenol (PCP); (PCP); (b) 2,4,6-trichorophenol (b) 2,4,6-trichorophenol (2,4,6-TCP); (2,4,6-TCP); (c) (c) lindane;lindane; ( d(d)) diazinon; diazinon; ((ee)) linuron;linuron; ( (ff)) trifluralin; trifluralin; (g ()g paraquat,) paraquat, illustrating illustrating the thespatial spatial orientation orientation and and size ofsize the of functionalthe functional groups. groups. Previously,Previously, our our laboratory laboratory has has conductedconducted a series series of of intervention intervention studies studies showing showing that that montmorillonite clay is safe for short-term human and animal consumption [22]. The idea of montmorillonite clay is safe for short-term human and animal consumption [22]. The idea of including clay-based sorbents in the diet has been fueled by the historical perspective that clay includingminerals clay-based and other sorbents sorbent inmaterials the diet have has been been co fueledmmonly by used the historical as ancient perspective medicine for that humans clay and minerals and otheranimals
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