Pesticides chlorinated hydrocarbon insecticides

Pesticides. Chlorinated hydrocarbon pesticides (qv) are often found in feed or water consumed by cows (19,20) subsequently, they may appear in the milk, where they are not permitted. Tests for pesticides are seldom carried out in the dairy plant, but are most often done in regulatory or private specialized laboratories. Examining milk for insecticide residues involves extraction of fat, because the insecticide is contained in the fat, partitioning with acetonitrile, cleanup (FlorisH [26686-77-1] column) and concentration, saponification if necessary, and determination by means of paper, thin-layer, microcoulometric gas, or electron capture gas chromatography (see Trace and residue analysis). 

The relative immobility of the chlorodioxins is expected, based on the very low solubility of these compounds in water (0.6 / g/liter). In contrast, the herbicide, 2,4,5-T, is relatively mobile in sandy soils, but movement decreases as soil organic matter increases. What does this information tell us, and how does it compare with other organic compounds A mobility scale has been devised for a large number of pesticides (3). Higher mobility numbers reflect increased compound mobility in soils. The dioxins would be in Class 1—i.e., they are immobile in soils and would compare with several chlorinated hydrocarbon insecticides. 

Analysis of PDP data from 1994 to 1999 showed that 73% of approximately 27,000 food samples that had no market claim (conventional or organic) showed detectable residues, while 23% of 127 fresh food samples designated as organic had detectable residue levels (Baker et al., 2002). Unavoidable contamination of some of the organic samples was due to the presence of persistent chlorinated hydrocarbon insecticides, which had been banned several years earlier, but 13% of the organic samples showed residues of pesticides other than the chlorinated hydrocarbon insecticides. 

Smith A.G., (1991) Chlorinated hydrocarbon insecticides, in Handbook of Pesticide Toxicology, (eds W.J. Hayes and... 

Smith, A.G., 1991. Chlorinated hydrocarbon insecticides. In Hayes Jr., W.J., Laws Jr., E.R. (Eds.), Handbook of Pesticide Toxicology Volume 2, Classes of Pesticides. Academic press, Inc, Toronto, pp. 731-916. 

Approximately 300 organic pesticide chemicals are being marketed in more than 10,000 different formulations. Last year over 750 million pounds were used in the United States. Insecticides account for nearly half this amount, but herbicides will far surpass them in tonnage within a few years. The chlorinated hydrocarbon insecticides have attracted attention because of their so-called persistence However, unlike some of their inorganic predecessors, organic pesticides are decomposed in the environment by biological and physicochemical processes which influence the amounts that will be found in the environment. Their mere presence in the environment does not necessarily jeopardize the public health. The amounts present, their toxicities, and the rate of detoxification and decomposition must be considered to assess their significance in the environment... 

Of the 750 million pounds of pesticides used in 1964, insecticides accounted for nearly half, with herbicides and fungicides comprising most of the balance (23). The markets for fungicides and chlorinated hydrocarbon insecticides have apparently reached a peak while the markets for organophosphorus insecticides and herbicides are increasing. It is predicted that the domestic use of herbicides will far surpass that of insecticides within a few years. 

These findings are highly significant. The fact that domestic usage of the chlorinated hydrocarbon insecticides has reached a peak and is on the decline can only mean that the maximum amounts of this class of pesticide chemicals in the environment have already been reached and can only decline in the future. It stands to reason, therefore, that the residue levels of these compounds have reached a peak in the fatty tissues of humans, wildlife, and domestic animals that have had access to residues of these pesticide chemicals in the environment and are probably declining. From the standpoint of public health, there is not one shred of evidence that the traces of these compounds in the body fat have any detrimental effect. Of course, it cannot be stated absolutely that some effect will not be discovered in the future. However, by the same token, it cannot be stated absolutely that this effect will not be beneficial ... 

Because of the prowess of the analytical chemist, it is now possible to find residues of the chlorinated hydrocarbon insecticides in the environment at concentrations of a few parts per trillion. He is not so adept at finding nanogram quantities of some of the other classes of compounds for many pesticides, the metabolites are not identified, so he doesn t know what to look for. There is little question, however, that many of the compounds that now escape detection are present in the environment, and it is only a matter of time until the analytical chemist finds them. 

A critical pesticide residue problem today is that of chlorinated hydro-carbon pesticides in milk. The easiest solution to this problem is an across-the-board restriction on the use of chlorinated hydrocarbon pesticides in any environment which might contaminate dairy animals or feeds. This type of restriction would doubtless create hardships on other agricultural enterprises in those areas and may in fact be unnecessary. Detailed examination of the possible sources may well point to solutions which will not sweepingly encompass all chlorinated hydrocarbon insecticides or all uses of them. 

Unlike the nonspecific effects and uncommon occurrence of direct mortality observed in wildlife exposed to chlorinated hydrocarbon pesticides, several studies have documented direct mortality from exposure to OP and carbamate insecticides. The method by which the OPs and carbamate insecticides affect wildlife is quite different from the method by which the chlorinated hydrocarbon insecticides effect wildlife. The OPs and carbamates inhibit cholinesterase, primarily acetylcholinesterase (AChE), which is an enzyme that functions in the breakdown of the neurotransmitter acetylcholine. Acetylcholine functions in the transmission of nerve impulses. Therefore, when AChE is inhibited by an OP or carbamate insecticide, it can no longer breakdown acetylcholine and there is continued transmission of nerve impulses that eventually leads to nerve and muscle exhaustion. The respiratory muscles are a critical muscle group that is affected, often leading to respiratory paralysis as the immediate cause of death. A major difference in the mode of action between OPs and carbamates is that the inhibition of AChE by OPs is, from a biological standpoint, irreversible, while the inhibition from exposure to carbamates is reversible in a biologically relevant time frame. There... 

Hayes WJ (1982) Chlorinated hydrocarbon insecticides. In Pesticides Studied in Man, pp. 172-283. Baltimore, MD Williams and Wilkins. 

The pesticides most frequently responsible for equine poisonings are the organophosphate, carbamate, and chlorinated hydrocarbon insecticides. Both the organo-phosphates and the carbamates are acetylcholinesterase inhibitors and present clinical pictures similar to those seen in food-producing animals. Affected horses salivate and sweat profusely and have muscle incoordination and ataxia. The chlorinated hydrocarbons are strong CNS stimulants affected horses become hyperalert, then excited, and, in severe cases, develop convulsions. In almost all instances, the mode of horses being exposed to pesticides is topical. 

Lotti M, Becker CE, Aminoff MJ, et al Occupational exposure to the cotton defoliants DEF and Merphos. J Occup Med 25 517-522, 1983 Markowitz SB Poisoning of an urban family due to misapplication of household orga-nophosphate and carbamate pesticides. Clin Toxicol 30 295-303,1992 Mayersdorf A, Israeli R, Beer-Sheva I Toxic effects of chlorinated hydrocarbon insecticides on the human electroencephalogram. Arch Environ Health 28 159-163,... 

Joy RM Chlorinated hydrocarbon insecticides, in Pesticides and Neurological Diseases. 

Biotransformation of certain chlorinated hydrocarbon insecticides results in their conversion to metabolites which are less polar than the parent chemical. Heptachlor and aldrin are converted to the more lipophilic compounds heptachlor epoxide and dieldrin, respectively, whereas DDT is converted to DDE. The primary residue of DDT, which persists to the present day in animals and humans after exposure over a decade ago, is DDE. Following biotransformation, these compounds distribute to tissues which are higher in neutral lipid content than are the major organs of metabolism and excretion, the liver and kidney. These lipid-rich tissues are relatively, deficient in the so-called mixed-function oxidase (MFO) enzyme systems necessary for biotransformation of the halogenated hydrocarbons to more polar and thus more easily excreted compounds. As a result, these lipophilic chemicals remain unchanged in adipose tissue with only limited amounts returning to the circulation for possible metabolism and excretion. Paradoxically, aldrin and heptachlor metabolism results in an increased rather than reduced body load. This is opposite of the pattern seen for most other pesticide classes. 

These classes of pesticides are among the most widely used and studied insecticides. They are defined based on their mechanism of activity, which is to inhibit the cholinesterase enzyme found in nerve junctions (synapses). Their major advantage over the chlorinated hydrocarbons insecticides are their much shorter biological and environmental half-lives, which are measured in hours and days rather than months or years. However, the trade-off is that they... 

Table III lists some common pesticides which have been widely reported to be extracted from water. The aqueous solubilities of pesticides vary within wide limits many, including chlorinated hydrocarbon insecticides, probably do not even occur as such in water but are always adsorbed to silt or other particles or dissolved in surface films (24). Overall concentrations, nevertheless, generally do not exceed the parts per trillion range—i.e., nanomolar (lO M). Reagents such as oxygen, hydroxide ion, and even metal ions normally are present in from perhaps 100- to 100,000-fold molar excess over the amounts of pesticides which are to be found in water (Table II).

Water as Reaction Medium. Being transparent to the near-ultraviolet spectrum of sunlight, pure water can serve as an inert medium in which pesticide transformations take place. For example, Henderson and Crosby (28) have shown that suspensions of the chlorinated hydrocarbon insecticide dieldrin (I), although essentially insoluble in water, undergo a photocondensation reaction to give photodieldrin (II) (Equation 2). 

Neurological Effects. A major incident of occupationally-related illness associated with a pesticide involved Kepone. Kepone is a chlorinated hydrocarbon insecticide used domestically as an ant and roach poison. In 1975, after workers at a plant... 

Chlorinated hydrocarbon insecticides (including Toxaphene, Lindane, Chlordane, DDT and Heptachlor) are among the most widely known and studied group of nonionic pesticides [90,101,102]. 

Environmental and health hazards associated with chlorine-based herbicides have impacted the production of these chemicals, and the consumption of chlorinated hydrocarbon insecticides has decreased by more than 95% since 1974. However, as this market segment constitutes < 1 % of the total chlorine consumption, the chlorine industry is unlikely to be affected by the restrictions on the Cl2-based agricultural chemicals, although debates and discussions on the pesticides have created a bad public image for the chemical industry. 

Paraquat Pesticides (includes acaricides, avicides, bactericides, insecticides, molluskicides, nematocides, piscicides, rodenticides) L S Chlorinated hydrocarbons (q.v.) Carbamates (q.v.) Organophosphorus compounds (q.v.) Herbicide... 

---