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Methoxychlor
Published in Philip H. Howard, Edward M. Michalenko, William F. Jarvis, Dipak K. Basu, Gloria W. Sage, William M. Meylan, Julie A. Beauman, D. Anthony Gray, Handbook of Environmental FATE and EXPOSURE DATA, 2017
Philip H. Howard, Edward M. Michalenko, William F. Jarvis, Dipak K. Basu, Gloria W. Sage, William M. Meylan, Julie A. Beauman, D. Anthony Gray
Summary: Release of methoxychlor to the environment is expected to occur primarily due to its use as an insecticide. Other sources of release may include loss during manufacturing, formulation, packaging, and disposal of methoxychlor. If released to soil, methoxychlor is expected to remain primarily in the upper layer of soil. Field studies have shown that methoxychlor does not leach significantly in soil. Degradation studies have shown that methoxychlor degrades more rapidly under flooded/anaerobic conditions than under nonflooded/aerobic conditions. Major degradation products are dechlorinated methoxychlor (DMDD) and mono- and di-hydroxy derivatives of methoxychlor and DMDD. Residual levels of methoxychlor have been detected in field studies 12-14 months after applications. Although the percentage of methoxychlor removed from fields by runoff losses may be small, it may be an important transport process since methoxychlor has been detected in many receiving waters. Methoxychlor volatilizes from terrestrial surfaces at a slow rate, but this process may contribute to an environmental cycling of the compound. If released to water, methoxychlor may be removed or transported by several different mechanisms. Methoxychlor may adsorb to suspended solids and sediments or it may bioaccumulate in certain aquatic organisms, although fish are reported to metabolize methoxychlor fairly rapidly. Rapid partitioning from water to sediments has been observed during laboratory studies. Although direct photolysis in water is not environmentally important, photosensitized photolysis may occur relatively rapidly (half-life of several hours) in various natural waters. Volatilization from water is unlikely to be important if strong adsorption to sediment occurs. Methoxychlor can biodegrade in water under anaerobic conditions (half-life < 28 days in sediments) or aerobic conditions (half-life >100 days in sediments). The rate of biodegradation increases with a decrease in oxygen availability. Aquatic hydrolysis is relatively slow as estimated half-lives range from 270 to 367 days at 27 °C If released to the atmosphere, methoxychlor may exist in either vapor or particulate form. Vapor-phase methoxychlor is expected to degrade relatively rapidly by reaction with photochemically produced hydroxyl radicals (estimated half-life of 6.75 hr); however, atmospheric methoxychlor may occur primarily in either a particulate or a water-bom phase. Monitoring data indicate that removal from air via precipitation is important. The detection of methoxychlor in remote Canadian rainwater and snow suggest that it is persistent in air and can be transported long distances. Methoxychlor may undergo an environmental cycling process that begins by its volatilization into air, followed by removal via precipitation, followed re-volatilization. The most probable route of exposure to methoxychlor would be inhalation or dermal contact during home or occupational use of this insecticide, inhalation of airborne particulate matter containing methoxychlor or ingestion of food or drinking water contaminated with methoxychlor. The US Food and Drug Administration (FDA) estimated average daily intake of methoxychlor Fiscal year 1981/1982 0.004 ug/kg body wt/ day.
Photocatalytic degradation of organic pollutants in wastewater by heteropolyacids: a review
Published in Journal of Coordination Chemistry, 2021
Zhang Chengli, Ma Ronghua, We Qi, Yang Mingrui, Cao Rui, Zong Xiaonan
Organochlorine pesticides have been widely used worldwide to control agricultural pests and vector-borne diseases [21]. Among the commonly used organochlorine pesticides, dichlorodiphenyltrichloroethane (DDT) [22], hexachlorocyclohexane (HCH), endosulfan, aldrin, chlordane, dieldrin, and endogenous Heptachlor, Mirex, Hexachlorobenzene (HCB), Toxaphene, Methoxychlor and Alachlor are persistent organic pesticides [23]. Organochlorine pesticides are very stable compounds, and their half-life can range from several months to several years [24]. In some cases, the half-life can be as long as several decades. It is estimated that the degradation time of DDT in the soil is 4 to 30 years, while other organochlorine pesticides may remain stable for many years after use [25]. Since they cannot be decomposed in the environment, their degradation is limited to chemical [26], physical, biological and microbiological means [27]. Organochlorine pesticides are fat-soluble compounds and can bioaccumulate in the fatty parts of the food chain's biota (such as breast milk, blood, and fatty tissues), causing humans to be exposed to these by eating contaminated soil or water in contact with food. The influence of trace pollutants [28] causes serious diseases to humans, but are also highly toxic to most aquatic organisms and soil microflora [29].
The effect of typhoons on POPs in atmospheric particulates over the coastal islands of Fujian, southeast China
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Qibin Lao, Liping Jiao, Liqi Chen, Xia Sun, Fajin Chen, Guoqiang Liu, Chunhua Zhang
The toxicity assessment of OCP was also calculated by the equations described in risk assessment. When the average daily dose (ADD) <10−6 indicated a very low risk, and the values >10−4 indicated a high potential health risk, and the values between 10−6 and 10−4 denoted a potential risk (Ge et al.2013; Ding et al.2015). The calculated ADD of each OCP compound was showed in Table 1. Except for the typhoon Chanchu, the estimated cancer risks for DDT, chlordane, endosulfan, aldrin, dieldrin, endrin, and methoxychlor are <10−6, indicating the potential effect of those OCP compounds could be negligible. But the ADD values of each OCP compounds were between 10−6 and 10−4 during the typhoon Chanchu period, suggesting that a potential risk during the period. In addition, the estimated for total accumulation of OCPs was above the threshold value (10−4) during the typhoon Chanchu period indicated a high potential health risk.
Investigation of associations between exposures to pesticides and testosterone levels in Thai farmers
Published in Archives of Environmental & Occupational Health, 2018
Parinya Panuwet, Chandresh Ladva, Dana Boyd Barr, Tippawan Prapamontol, John D. Meeker, Priya Esilda D'Souza, Héctor Maldonado, P. Barry Ryan, Mark G. Robson
There have been several animal studies that reported links between exposure to other pesticides and testosterone levels.36–40 For these studies, pesticides of interest included methyl-parathion, chlorpyrifos, chlorpyrifos-methyl, diazinon, profenofos, glyphosate, piperophos, methoxychlor, cypermethrin, and malathion. The majority of these studies agreed that exposures to these pesticides contributed to a reduction in testosterone levels in experimental settings. Still, there are other interesting results. For example, exposure to metolachlor, another chlorophenoxy herbicide, has been shown to increase serum testosterone levels in rats.41 Table S2 (supplemental material) summarizes the key findings of animal and in vitro studies. Note that several studies have provided information about plausible mechanisms of testosterone reduction following exposure to some pesticides. For example, Viswanath et al42 were able to demonstrate, using the NIH3T3 cell line, that piperophos and chlorpyrifos inhibited the biosynthesis of testosterone by disrupting CYP11A1, HSD3B, and HSD17 B3 and decreasing StAR protein expression. In addition, they found that chlorpyrifos could decrease LH receptor-stimulated cAMP production. Other pesticides that could inhibit biosynthesis of testosterone by disruption of its associated enzymes included methoxychlor and its bioactive metabolite 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (HPTE).27