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Names | |
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Preferred IUPAC name Dimethyl 2,3,5,6-tetrachlorobenzene-1,4-dicarboxylate | |
Other names Chlorthal-dimethyl; Dimethyl 2,3,5,6-tetrachloroterephthalate | |
Identifiers | |
3D model (JSmol) | |
ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.015.877 |
EC Number |
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KEGG | |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
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Properties [1] | |
C10H6Cl4O4 | |
Molar mass | 331.95 g·mol−1 |
Appearance | Colourless to grey crystalline powder |
Density | 1.56 |
Melting point | 156 °C (313 °F; 429 K) |
Boiling point | 345 °C (653 °F; 618 K) |
0.21 mg/L (20 °C) | |
log P | 4.28 |
Vapor pressure | 0.21 mPa (2.5 x 10−6 Torr) |
Hazards | |
NFPA 704 (fire diamond) | |
Flash point | Nonflammable |
N/A | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | >10000 mg/kg [2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Dimethyl tetrachloroterephthalate (DCPA, with the main trade name Dacthal) is an organic compound with the formula C6Cl4(CO2CH3)2. It is the dimethyl ester of tetrachloroterephthalic acid, used as a preemergent herbicide with the ISO common name chlorthal-dimethyl. [3] [1] [4] It kills annual grasses and many common weeds without killing sensitive plants such as turf grasses, flowers, fruits, vegetables, and cotton. [5]
DCPA was first registered for use in the United States in 1958, for use on turf grasses, for the control of annual grasses such as crabgrass, and certain annual broad-leaved weeds. [5] [6] Production of DCPA was eventually discontinued by ISK Biosciences in 1998, but the large manufacturing company AMVAC (American Vanguard Corporation) began producing the product in 2001 for use in America. [7] EPA registration for some uses, including on vegetable crops, was voluntarily terminated by the manufacturer in 2005 in response to EPA concerns regarding the contamination of groundwater. [5] [8]
In Australia, DCPA is the active ingredient in agchem company Farmalinx's herbicide called Dynamo 750. [9]
The use of DCPA as a herbicide was first described in a patent filed in 1958. [10] The material was prepared as had been described in 1948 by treating terephthaloyl chloride with chlorine to give 2,3,5,6-tetrachloroterephthaloyl chloride, followed by ester formation with methanol. [11]
DCPA is released directly into the environment during its use as a herbicide. DCPA exists in both the vapor and particulate phases when exposed to the air. In the vapor phase, DCPA should react slowly with hydroxyl radicals with an estimated half-life of 36 days. Particulate-phase DCPA may be physically removed from air by wet and dry deposition. With a high Koc of 3900, DCPA is presumably immobile in soil, and thus may strongly attach to inorganic material in soil and other environments. [8]
In addition, its breakdown products, TPA (Tetrachloroterephthalic acid) and MTP (Monomethyl tetrachloroterephthalic acid), enter the environment after being formed through various processes. Studies have shown that DCPA can partially degrade through volatilization, as well as via photodegradation, but biodegradation is the primary route of DCPA degradation leading to MTP and TPA. Environmental Protection Agency testing in New York showed "measurable residues of DCPA and degradates" on land that had endured five years of treatment with DCPA, followed by three years of no treatment. DCPA is also prevalent in water and bioconcentration is seen in aquatic animals. DCPA accumulation was shown in fish at "several locations" in the United States. [8] Some of these locations included the Apalachicola, Colorado, Mobile, Savannah, and Pee Dee River Basins in both bass and carp. In the study done on these river basin locations, roughly 39% of the fish tested had stored DCPA concentrations that exceeded their limit of detection, and the male fish had higher stored concentrations of DCPA than their female counterparts. [12] Fish collected from different locations throughout the United States are often contaminated by DCPA if they are near agricultural areas that use or have used it as an herbicide. [13]
Humans are exposed to DCPA through drinking well water, eating fish, and eating leafy and root vegetables. In some areas where agriculture is prominent, inhalation of air can be a means of exposure. DCPA is listed as a Group C Possible Human Carcinogen by the National Library of Medicine. [14]
DCPA degrades via successive hydrolysis of the two ester linkages, first forming monomethyl tetrachloroterephthalate (MTP) then further to tetrachloroterephthalic acid (TPA). Following ingestion, MTP is predominantly formed in the gastrointestinal tract and TPA is formed in other tissues during the metabolism of DCPA. [15] [16]
DCPA shows no chemical degradation in water that has a pH between 5.0 and 9.0. However, in the presence of sunlight, the half-life for DCPA on the surface of the water is less than three days. In soil, the half-life in the presence of sunlight ranges from 14 to 100 days. [5]
TPA and MTP are both more water-soluble than DCPA, and readily leach into groundwater wherever DCPA is used, regardless of soil composition. TPA has been observed to cause weight loss and diarrhea in laboratory rats, the same symptoms caused by DCPA, but at lower doses than necessary for DCPA. [8] TPA does not degrade, and infiltrates soil and nearby water sources. The accumulation of TPA and its salts in areas where DCPA is widely used has prompted research on TPA, although no carcinogenicity studies have been conducted yet. [17] There have been no standard toxicity studies identified for MTP. [18]
Studies show that DCPA and TPA may cause detrimental health effects in laboratory animals, mainly weight loss and diarrhea occurring at doses of 2000 mg/kg/day. There were also effects on the lungs, liver, kidney, and thyroid glands of male and female rats. The LD50, or 50% lethal dose of DCPA, is 12,500 mg/kg in spartan rats, and greater than 10,000 mg/kg in beagle dogs. In humans, it seems that DCPA is poorly absorbed, as 6% of a 25-mg dose and 12% of a 50-mg dose were absorbed according to metabolites in urine. Decreased motor activity and poor sight reflexes were also observed in a study on New Zealand white rabbits that were exposed to DCPA. There were no physical developmental effects in the offspring of pregnant rats exposed to DCPA. [8] Rats whose mothers were exposed to DCPA during pregnancy had impaired higher-level learning test scores than those whose mothers were not exposed. [14] Studies regarding the carcinogenicity of DCPA have produced mixed results. A study by ISK Biotech Corp. in 1993 showed DCPA leading to thyroid tumors in male and female rats, and liver tumors in female rats. Alternatively, a 1963 study using pure DCPA did not produce any negative results when administered to albino rats. [8]
Studies have demonstrated that DCPA acts as a chemical disruptor by interfering with microtubule formation in exposed cells. This interference results in abnormal cell division. The abnormal microtubules affect cell wall formation as well as chromosome replication and division. [19] The key difference between DCPA and other mitotic inhibitors is that it often produces multinucleate cells. [20] It essentially kills plants by inhibiting cell division in this manner. [19]
Exposure to DCPA has shown damaging effects in the adrenal glands, kidneys, livers, thyroids, and spleens of laboratory animals. [19] The effects on the rabbits included decreased motor activity and poor reflexes. [8]
In the U.S. The Safe Drinking Water Act of 1996 has the U.S. EPA publish a list of contaminants referred to as the Contaminant Candidate List to assist in research efforts. The Safe Drinking Water Act also calls for the EPA to choose five contaminants from the list and determine whether regulation is necessary. In July 2008, the EPA determined that no regulatory action is necessary for DCPA mono-acid (MTP) degradate and DCPA di-acid (TPA) degradate. After multiple studies, it was determined that degradates of DCPA appear too infrequently to pose a serious health risk so the government does not regulate DCPA or its degradates in drinking water. [21] Public water systems are also not required to monitor DCPA, MTP, or TPA. There are standards set by some states ranging from 0.17 µg/L to 2 µg/L. [18]
Some uses of DCPA, particularly on vegetable crops, were voluntarily terminated by the chemical's registrant in 2005, in response to the EPA's concerns regarding DCPA and TPA contamination of groundwater. [8]
In California, DCPA products are required to be labeled with the information that products with DCPA also contain trace amounts of Hexachlorobenzene (HCB) which is a chemical known to the State of California to cause cancer or birth defects. [22]
Glyphosate is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSP). It is used to kill weeds, especially annual broadleaf weeds and grasses that compete with crops. Its herbicidal effectiveness was discovered by Monsanto chemist John E. Franz in 1970. Monsanto brought it to market for agricultural use in 1974 under the trade name Roundup. Monsanto's last commercially relevant United States patent expired in 2000.
Bifenthrin is a pyrethroid insecticide. It is widely used against ant infestations.
Dicofol is an insecticide, an organochlorine that is chemically related to DDT. Dicofol is a miticide that is very effective against spider mite. Its production and use is banned internationally under the Stockholm Convention.
Alachlor is an herbicide from the chloroacetanilide family. It is an odorless, white solid. The greatest use of alachlor is for control of annual grasses and broadleaf weeds in crops. Use of alachlor is illegal in the European Union and no products containing alachlor are currently registered in the United States.
Atrazine is a chlorinated herbicide of the triazine class. It is used to prevent pre-emergence broadleaf weeds in crops such as maize (corn), soybean and sugarcane and on turf, such as golf courses and residential lawns. Atrazine's primary manufacturer is Syngenta and it is one of the most widely used herbicides in the United States, Canadian, and Australian agriculture. Its use was banned in the European Union in 2004, when the EU found groundwater levels exceeding the limits set by regulators, and Syngenta could not show that this could be prevented nor that these levels were safe.
Benomyl is a fungicide introduced in 1968 by DuPont. It is a systemic benzimidazole fungicide that is selectively toxic to microorganisms and invertebrates, but relatively nontoxic toward mammals.
Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one hydrogen atom by an atom of iodine. It is naturally emitted by rice plantations in small amounts. It is also produced in vast quantities estimated to be greater than 214,000 tons annually by algae and kelp in the world's temperate oceans, and in lesser amounts on land by terrestrial fungi and bacteria. It is used in organic synthesis as a source of methyl groups.
Endrin is an organochlorine compound with the chemical formula C12H8Cl6O that was first produced in 1950 by Shell and Velsicol Chemical Corporation. It was primarily used as an insecticide, as well as a rodenticide and piscicide. It is a colourless, odorless solid, although commercial samples are often off-white. Endrin was manufactured as an emulsifiable solution known commercially as Endrex. The compound became infamous as a persistent organic pollutant and for this reason it is banned in many countries.
Soil contamination, soil pollution, or land pollution as a part of land degradation is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste. The most common chemicals involved are petroleum hydrocarbons, polynuclear aromatic hydrocarbons, solvents, pesticides, lead, and other heavy metals. Contamination is correlated with the degree of industrialization and intensity of chemical substance. The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapour from the contaminants, or from secondary contamination of water supplies within and underlying the soil. Mapping of contaminated soil sites and the resulting clean ups are time-consuming and expensive tasks, and require expertise in geology, hydrology, chemistry, computer modelling, and GIS in Environmental Contamination, as well as an appreciation of the history of industrial chemistry.
Methoxychlor is a synthetic organochloride insecticide, now obsolete. Tradenames for methoxychlor include Chemform, Maralate, Methoxo, Methoxcide, Metox, and Moxie.
Dimethyl phthalate (DMP) is an organic compound and phthalate ester. it is a colourless and oily liquid that is soluble in organic solvents, but which is only poorly soluble in water.
Dinoseb is a common industry name for 6-sec-butyl-2,4-dinitrophenol, a herbicide in the dinitrophenol family. It is a crystalline orange solid which does not readily dissolve in water. Dinoseb is banned as an herbicide in the European Union (EU) and the United States because of its toxicity.
Drinking water quality in the United States is generally safe. In 2016, over 90 percent of the nation's community water systems were in compliance with all published U.S. Environmental Protection Agency standards. Over 286 million Americans get their tap water from a community water system. Eight percent of the community water systems—large municipal water systems—provide water to 82 percent of the US population. The Safe Drinking Water Act requires the US EPA to set standards for drinking water quality in public water systems. Enforcement of the standards is mostly carried out by state health agencies. States may set standards that are more stringent than the federal standards.
1,2,3-Trichloropropane (TCP) is an organic compound with the formula CHCl(CH2Cl)2. It is a colorless liquid that is used as a solvent and in other specialty applications.
2,4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula Cl2C6H3OCH2CO2H. It is usually referred to by its ISO common name 2,4-D. It is a systemic herbicide that kills most broadleaf weeds by causing uncontrolled growth, but most grasses such as cereals, lawn turf, and grassland are relatively unaffected.
Imazaquin is an imidazolinone herbicide, so named because it contains an imidazolinone core. This organic compound is used to control a broad spectrum of weed species. It is a colorless or white solid, although commercial samples can appear brown or tan.
Bentazon is a chemical manufactured by BASF Chemicals for use in herbicides. It is categorized under the thiadiazine group of chemicals. Sodium bentazon is available commercially and appears slightly brown in colour.
Glyphosate-based herbicides are usually made of a glyphosate salt that is combined with other ingredients that are needed to stabilize the herbicide formula and allow penetration into plants. The glyphosate-based herbicide Roundup was first developed by Monsanto in the 1970s. It is used most heavily on corn, soy, and cotton crops that have been genetically modified to be resistant to the herbicide. Some products include two active ingredients, such as Enlist Duo which includes 2,4-D as well as glyphosate. As of 2010, more than 750 glyphosate products were on the market. The names of inert ingredients used in glyphosate formulations are usually not listed on the product labels.
Cyanazine is a herbicide that belongs to the group of triazines. Cyanazine inhibits photosynthesis and is therefore used as a herbicide.
Ohio River Park is a Superfund Site located in Neville Island, Pennsylvania. Between the 1920s-1970s, the Site was used for municipal waste, pesticide manufacturing, coke sludge disposal, cement manufacturing disposal, and pesticide waste. In 1977, Neville Land Company donated the Site to Allegheny County who started developing the Site as a community park. In 1979, Allegheny County found various hazardous contaminants on the Site. On August 30, 1990, the Site was determined to be a Superfund Site due to VOCs, SVOCs, inorganics, and pesticides being present in the surface soil, subsurface soil, surface water, river sediment, and groundwater. Soil remediation began in February 1998 and ended in September 1999. Today, Ohio River Park has the Robert Morris University Island Sports Center and Coraopolis Bridge on top of it. Additionally, benzene continues to be monitored because it is still present in the Site's groundwater.