Chlorinated pesticides environmental concerns

In this volume of Issues we address the sources, environmental cycles, uptake, consequences and control of many of the more important chlorinated organic micropollutants. Under this heading we have included a range of semi-volatile persistent compounds, notably polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) as well as a number of chlorinated pesticides. We have not sought to include volatile species such as CFCs which cause environmental problems of an entirely different nature. The compounds included in this volume cause no threat to the stratospheric ozone layer, but have given widespread cause for concern in relation to their environmental persistence and high toxicity, and their potential for adverse effects on humans and wildlife. 

The QuEChERS method was invented and described for the first time in 2003 by Anastassiades et al. [98] as a fast, simple, inexpensive, and convenient preparation procedure for fruit and vegetable samples used for pesticide multiresidue analysis. Currently, this methodology is used for determinations of pesticides, pesticide residues, and other compounds of environmental concern such as phenol derivatives, perfluorinated compounds, and chlorinated hydrocarbons pharmaceutical compounds in food and agricultural matrices and environmental samples such as soil, sediments, and water (see for example [99-102]). 

Simultaneous exposure of rats to Aroclor 1254 or 1260 and chemicals of environmental concern such as the pesticides mirex, photomirex, and/or kepone in the diet resulted in increased severity of the liver lesions attributed to exposure to chlorinated biphenyls alone (Chu et al. 1980). Induction of hepatic AHH activity by Aroclor 1254 in the diet of lactating rats was increased in an additive manner by simultaneous dietary exposure to polybrominated biphenyls such as Firemaster BP-6 (McCormack et al. 1979). 

These chemicals are considered in a pollution category because both deliberate and accidental release to the environment of several of these types of compounds, for example the industrial chemicals such as PCBs (polychlorinated biphenyls) and the chlorinated pesticides p,p DDT (dichlorodiphenyl-trichloroethane formal chemical name l,l -(2,2,2-trichloroethylidene)-bis (4-chlorobenzene)), have had unintended adverse environmental effects on diverse plants and animals and on people. Initially, chemicals such as PCBs and DDT were beneficial to human civilization PCBs as industrial chemicals allowing economical, safe delivery of electricity, and DDT as a pesticide eradicating vector pests of human health concern and agricultural crop pests. Only after these chemicals had entered widespread use did it become apparent that there were environmental problems, although in hindsight there was evidence of potential problems early in the history of their manufacture and use. 

The use of chlorinated pesticides is expected to decline because of environmental concerns. The toxic effects associated with pentachlorophenol will impact its production and, in turn, the chlorine consumption in this market. ITie use of chlorine in producing chlorinated isocyanurates, chlorinated paraffins, and ethyleneamines is projected to grow over the next several years. However, the market for cyanuric chloride is expected to decline as a result of the flat demand for its primary derivative, triazine herbicides. 

Of major concern are the health and environmental impacts of the abundant chlorinated and brominated hydrocarbons (ref. 2). These materials have numerous industrial applications as pesticides, solvents, propellants, refrigerants, plastics, fire retardants and extinguishers, disinfectants for drinking water, pharmaceuticals and electronic chemicals. Many chemical manufacturers utilize chlorinated and brominated organics as intermediates. It is estimated, for instance, that almost 85 % of the pharmaceuticals produced in the world require chlorine at some stage of synthesis. 

NOTE Chlorine is widely used in the protection of drinking water, the manufacture of pharmaceuticals, crop pesticides, paper, rubbers, resins and plastics, and thousands of other products. Nevertheless, since the early 1990s, there has been a groundswell of opinion to either ban or severely limit the use of chlorine in all manners of processes. This is based on observations associated with the probable adverse effect to the environment from certain chlorinated organic chemicals, such as polychlorinated biphenyl (PCB) and the insecticide DDT. There is also concern in a number of other areas, for example, that free chlorine may contribute to effluent toxicity due to the formation of chloramines and trihalomethanes (THMs). In the United States in 1993 to 1994, this opinion was fueled by the possibility that the Environmental Protection Agency (EPA) would... 

Ironically, those pressures of the last 13 years or so have generated more information about the environmental toxicology of chlorinated insecticides than we may ever gain about other classes of pesticides or environmental contaminants. As a side-benefit, we now know that some xenobiotics may be transferred into global areas they were never intended to reach and we have developed the methodology needed to measure these low level contaminations It is also doubtful whether the extensive background contamination by PCB would have come to light so quickly without the widespread concern about OC ... 

Chlorinated phenols are common environmental pollutants, introduced as pesticides and herbicides. Studies have been carried out on the potential use of radiation to destroy these compounds as a means of environmental cleanup . While these studies were concerned with mechanisms (and are discussed in the chapter on transient phenoxyl radicals), other studies involved large-scale irradiation to demonstrate the decomposition of phenol in polluted water . Continuous irradiation led to conversion of phenol into various degradation products (formaldehyde, acetaldehyde, glyoxal, formic acid) and then to decomposition of these products. At high phenol concentrations, however, polymeric products were also formed. 

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