Toxicology of Pesticides

L.1000. Costa , Thou. Aschner , in Reference Module in Biomedical Sciences, 2014

2,4-Dichlorophenoxyacetic Acid

two,4-Dichlorophenoxyacetic acrid (2,iv-D) is the most commonly used chemical compound among chlorophenoxy herbicides. These herbicides are chemic analogues of auxin, a constitute growth hormone, and produce uncontrolled and lethal growth in target plants. Considering auxin is critical to the growth of many wide-leaf plants, but is non used by grasses, chlorophenoxy compounds can suppress the growth of weeds without affecting the grasses. 2,4-D is ane of the most widely used herbicides throughout the world, and is primarily used in agriculture to control weeds in corn and grain, forestry, and backyard care practices. two,4-D has depression to moderate acute toxicity, though ingestion of doses ordinarily above 300 mg kg−1 has caused several cases of acute poisoning in humans. Vomiting, burning of the oral fissure, abdominal pain, hypotension, myotonia, and CNS interest including coma are among the clinical signs observed. Since 2,iv-D is an acid, alkalinization of the urine through intravenous administration of bicarbonate has been suggested to increase its elimination. Several case reports propose an association between exposure to 2,4-D and various neurologic furnishings, though potential underlying mechanisms are unknown. A few epidemiological studies have institute an association betwixt exposure to chlorophenoxy herbicides and non-Hodgkin's lymphoma or soft-tissue sarcoma, withal, an overall evaluation of all cohort and case–control studies available to date does non appear to provide an acceptable evidence to conclude that exposure to 2,4-D is associated with these cancers (Garabrandt and Philbert, 2002).

A related chemical compound of historical involvement is 2,iv,5-trichlorophenoxyacetic acid (2,4,5-T), which has been withdrawn from apply considering of concerns that arose from contagion of some formulations with 2,3,seven,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD tin can be derived from the reaction of 2 molecules of ii,4,5-trichlorophenol during the synthesis of 2,4,5-T. During the Vietnam State of war, a fifty:fifty mixture of the n-butyl esters of 2,iv-D and 2,3,5-T, known as Agent Orange (from the color of the barrels that contained it), was extensively used as a defoliant and found to be contaminated with TCDD to a maximum of 47 μg one thousand−1. Exposure of war machine personnel and Vietnamese population to Agent Orange has raised concerns on possible long-term health effects, specially carcinogenicity and reproductive toxicity, which are ascribed to the presence of TCDD. In dissimilarity, formulations of two,4-D contain extremely low levels of polychlorinated dibenzo-p-dioxins, usually beneath the limit of detection.

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Effect of Ecology Toxins on Spermatogonial Stem Cells

Kara E. McAbee , ... Hooman Sadri-Ardekani , in Bioenvironmental Issues Affecting Men's Reproductive and Sexual Health, 2018

2,4-Dichlorophenoxyacetic Acid

2,4-Dichlorophenoxyacetic acrid, more usually known equally 2,4-D, is a usually used herbicide worldwide. It has been used in the agricultural field for more than fifty   years [16]. The general population may be at risk because of modest amounts of the herbicide that contaminate oils, fats, and sugars in consumer food. It is a known carcinogenic substance in mammals, with some studies showing an increased adventure for non-Hodgkin's lymphoma and other malignant solid tumors [17,18]. Nevertheless, with respect to germ cells, there accept been several contradictory studies nearly its toxic potential [19–21].

Madrigal-Bujaidar et al. in 2001 [22] studied the frequency of SCEs in mouse spermatogonial cells treated with single oral doses of l, 100, or 200   mg/kg of two,iv-D (five mice per grouping). Two and half days afterward exposure, the spermatogonial cells of mice treated with the two higher doses (2.7 and 3.19 SCEs, respectively) showed pregnant increases in SCEs when compared with the negative control (1.53 SCE). Linear regression analysis showed that this chemical consecration was dose-dependent. The high-dose treatment group mice likewise exhibited other systemic signs such every bit motor depression and lower body temperature [22].

Mi et al. also studied the toxic effects of two,4-D on testicular cells but in vitro; they used a germ cell–somatic jail cell coculture model from embryonic chicken testes. They also sought to evaluate the potential attenuation of toxicity with the apply of quercetin, a dietary antioxidant. The cells were incubated in a medium containing two,4-D and assessed 48   h after. They looked at the morphology, jail cell number, and prison cell viability of the spermatogonial cells. At the concentration of 50   μg/mL 2,4-D, many spermatogonial cells showed condensed nuclei and vacuolated cytoplasm, indicating stressed cells. They besides plant a significant reduction in the number of spermatogonial cells equally compared with nontreated controls (500 vs. 750 spermatogonial cells per mmii). Interestingly, when quercetin was added to the medium (0.one–1   μg/mL), the spermatogonial cell morphology remained intact, with like cell numbers as the controls. The same was observed for cell viability, a reduction in cells treated with 2,4-D lone (lxx% viability) but a restored viability in combination with quercetin (100% viability) [23].

Both of these studies [22,23] proved that 2,4-D has a toxic effect on spermatogonial cells. Information technology is likely that it exerts this effect through the formation of costless radicals. Quercetin is a known antioxidant that abolishes NF-kB pathway, which blocks production of mediators involved in oxidative harm [24]. It seems that using quercetin in combination with 2,4-D attenuated the oxidative damage acquired by 2,four-D [23]. However, it is imperative that the herbicide 2,4-D remains regulated to maintain condom levels.

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Transgenic Plants and Found Biotechnology

David P. Clark , Nanette J. Pazdernik , in Biotechnology (2nd Edition), 2016

The compound 2,four-dichlorophenoxyacetic acid, or 2,4-D, is a herbicide used to impale any dicot constitute tissue. The substance is a constructed auxin, which is a type of plant hormone that is absorbed by the leaves of a plant. When a concentrated amount of the hormone is applied to a dicot, the tissues reply with uncontrolled and unsustained growth, which ultimately kills them. Although 2,4-D is very constructive for dicots or broad leaf plants, the substance has no effect on whatever monocots, such as wheat, corn, rice, and grass. That is why it is marketed as a grass herbicide that can kill weeds such equally dandelions but not damage the grass plants.

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T, two,iv,five-

L.P Weber , in Encyclopedia of Toxicology (Third Edition), 2014

Background

A combination of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-T (Agent Orange), was used past the US military during the Vietnam War for confusion. Long-term health consequences from exposure to Agent Orange, likely attributable to contamination of 2,4,5-T preparations with ii,3,seven,8-tetrachlorodibenzo-p-dioxin (TCDD) are suspected. Use of 2,4,five-T as a warfare agent was banned later on the Vietnam War and agricultural uses are suspended.

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Chlorophenoxy Herbicides

S. Karanth , in Encyclopedia of Toxicology (Third Edition), 2014

Background

A mixture of the chlorophenoxy herbicides 2,4-dichlorophenoxy acetic acid (two,4-D) and 2,4,5-trichlorophenoxy acerb acid (2,4,5-T), known equally Agent Orange, was extensively used by the Us military during Vietnam War in order to destroy forest and other vegetation from the premises of US bases. Well-nigh 19 1000000 gallons of Agent Orange was used on approximately three.half-dozen million acres of land in Vietnam and Laos during the catamenia from 1962 to 1971. Some lots of 2,4,5-T were contaminated with dioxins formed during manufacturing. Because dioxins resist deposition and remain in the environment for years, they are considered persistent organic pollutants. The principal dioxin present in Agent Orange, 2,three,vii,8-tetrachlorodibenzo-p-dioxin, or TCDD, is i of the nigh acutely toxic synthetic chemicals known. TCDD levels were found to exist higher amongst veterans serving in Vietnam compared to those serving elsewhere at the same time. Concerns that these and other health problems may accept been associated with exposure to Agent Orange stimulated a serial of scientific studies, wellness care programs, and compensation programs directed in support of veterans.

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Pesticides and Rice Agronomics

Balkrishna Tiwari , ... D.N. Tiwari , in Cyanobacteria, 2019

3.2.6 Synthetic Auxin

Synthetic auxin, that is, 2,4-dichlorophenoxyacetic acid (2,four-D) is the showtime herbicide, which was developed at the commercial scale to utilize as a broadleaf herbicide. It selectively kills dicots without affecting monocots. At lower doses, two,4-D acts as a plant growth promoter while at college doses it induces symptoms in plants like to those induced by higher doses of auxin (IAA). According to the The states Environmental Protection Agency (EPA), 2,four-D kills plants mainly in three ways: (i) altering the cell walls plasticity, (ii) influencing the protein synthesis, and (iii) increasing ethylene production. 2,four-D at the recommended doses causes uncontrolled and unsustainable growth in the plants that leads to the stem curlicue over, leaf withering, and ultimately the found death (Song, 2014).

Similar to the college plants, 2,4-D at the lower doses as well acts as a growth promoter and enhances the growth, while at the higher doses detrimental effects were observed in the blue-green alga. It has been reported that the growth of Synechococcus aeruginosus and synthesis of cellular metabolites were stimulated by 200   μg   mL−   1 of 2,4-D while further increase in its concentration (i.e., 500, 800, and m   μg   mL−   1) resulted to a gradual decrease in the growth (Bhagya Lakshmi, 2016). two,iv-D also promotes the growth and heterocyst frequencies of cyanobacterium N. linckia up to 100   mg   L−   1 concentration (Tiwari et al., 1980).

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Pesticides as Endocrine-Disrupting Chemicalsa

Tammy E. Stoker , Robert J. Kavlock , in Hayes' Handbook of Pesticide Toxicology (Third Edition), 2010

eighteen.4.1 2,4-D

2,4-D (2,4-dichlorophenoxyacetic acid) is a herbicide in the phenoxy or phenoxyacetic acid family that is used postemergence for selective control of broadleaf weeds. Residents and professional person applicators may apply ii,4-D on home lawns. At concentrations that exceed the dose for renal clearance post-obit chronic exposure, it has been shown to crusade hypothyroid state and thyroid tumors in rats. In addition, in that location is a significant suppression of thyroid hormone levels in ewes dosed with this chemical (Rawlings et al., 1998). Similar findings take been reported in rodents, with suppression of thyroid hormone levels, increases in thyroid gland weight, and decreases in weight of the ovaries and testes (Charles et al., 1996). The increases in thyroid gland weight are consistent with the suppression of thyroid hormones since the gland generally hypertrophies in an attempt to recoup for insufficient circulating levels of thyroid hormones. Thyroid hormone is known to play a critical part in the evolution of the brain. Slight thyroid suppression has been shown to adversely touch neurological development in the fetus, resulting in lasting effects on child learning and behavior (Haddow et al., 1999). 2,4-D causes slight decreases in testosterone release and significant increases in estrogen release from testicular cells (Liu et al., 1996). In rodents, this chemical also increases levels of the hormones progesterone and prolactin, and information technology causes abnormalities in the heat cycle (Sturtz et al., 2008). Male subcontract sprayers exposed to 2,4-D had lower sperm counts and more spermatic abnormalities compared to men who were not exposed to this chemical (Lerda and Rizzi, 1991).

2,4-D as well interferes with the neurotransmitters serotonin and dopamine. In young organisms, exposure to two,4-D results in delays in encephalon development and abnormal beliefs patterns, including apathy, decreased social interactions, repetitive movements, tremor, and immobility (Evangelista de Duffard et al., 1995). Females are more severely affected than males. Rodent studies have revealed a region-specific neurotoxic effect on the basal ganglia of the encephalon, resulting in an array of effects on critical neurotransmitters and adverse effects on behavior (Bortolozzi et al., 2001).

In addition, another report showed that two,4-D had an estrogen response in breast cancer cells (Lin and Garry, 2000). These investigators too evaluated the cellular and molecular developmental toxicity of two,4-D and other pesticides normally used in Cherry-red River Valley, Minnesota (Lin and Garry, 2000). In improver, a report from The Netherlands showed that ii,iv-D has the ability to readapt sexual activity hormones from the protein that usually transports these hormones in the claret (Meulenberg, 2002).

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Safety Assessment including Current and Emerging Bug in Toxicologic Pathology

Ramesh C. Gupta , James Due west. Crissman , in Haschek and Rousseaux's Handbook of Toxicologic Pathology (Third Edition), 2013

Source

This potent group of constructed phenoxy herbicides includes 2,4-dichlorophenoxyacetic acid (ii,4-D), which was released for commercial use in 1946 and is now 1 of the most commonly used herbicides in the world. During the Vietnam War era, it was mixed with a similar chlorophenoxy compound, 2,4,5-trichlorophenoxyacetic acid (2,iv,5-T), to make the defoliant Amanuensis Orangish. The chlorophenoxy herbicides are synthetic auxins, institute hormones that kill broadleaf plants (dicots) by stimulating uncontrolled growth; therefore, they are used for weed control in grass cereal grains (monocots), like rice and wheat. Dying plants may accumulate toxic levels of nitrate and cyanide. Genetic resistance to 2,four-D has been transferred to genetically engineered soybeans to provide an herbicidal alternative to glyphosate (discussed below).

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Plasmapheresis in Acute Intoxication and Poisoning

François Madore , Josée Bouchard , in Disquisitional Care Nephrology (3rd Edition), 2019

2,4-Dichlorophenoxyacetic Acid and Sodium Chlorate

The use of plasmapheresis has been reported in poisoning with 2,4-dichlorophenoxyacetic acrid 35 and sodium chlorate, 36 toxic components included in herbicides. Still, these substances are dialyzable because neither is highly protein jump. The beneficial upshot of plasmapheresis is thought to exist due to removal of cherry-red claret cell devastation products and hemoglobin, because these agents cause severe hemolysis. 4 Therefore plasmapheresis is not intended to clear the toxic compound, just it may be useful in removing free hemoglobin and claret jail cell droppings from the circulation. iv Most contempo reports or recommendations mention the use of hemodialysis for 2,4-dichlorophenoxyacetic acid or sodium chlorate poisoning only do not include any recommendation on plasmapheresis. 37–39

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Chlorophenoxy Herbicides*

Subramanya Karanth , in Encyclopedia of Toxicology (Second Edition), 2005

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Representative Chemicals: 2,iv-D (2,4-dichlorophenoxy acetic acid); ii,4-DP (2-(2,4-Dichlorophenoxy)propionic acid); 2,four,5-T (ii,4,5-Trichlorophenoxy acetic acrid); Dicamba (3,6-Dichloro-o-anisic acid); MCPA (four-Chloro-2-methyl-phenoxy acetic acid); MCPP (2-(four-Chloro-2-methylphenoxy)propionic acid); Silvex (two-(2,4,5-Trichlorophenoxy)propionic acid)

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Chemical Abstracts Service Registry Numbers: CAS 94-75-7 (2,4-D); CAS 120-36-five (ii,4-DP); CAS 93-76-5 (ii,4,v-T); CAS 94-76-iv (MCPA); CAS 93-65-two (MCPP); CAS 93-72-1 (Silvex); CAS 1918-00-ix (Dicamba)

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Chemical/Pharmaceutical/Other Form: Herbicides

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Chemical Structure (General):

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