Synthetic Pesticide Residues Research Articles

Contamination levels of organophosphorus and synthetic pyrethroid pesticides in cocoa beans from Ghana

The concentrations of pesticide residues in fermented dried cocoa beans were assessed from sixteen (16) selected cocoa farms in the Dormaa West District in the Brong Ahafo Region of Ghana. The samples were extracted and analysed for 13 organophosphorus and 9 synthetic pyrethroid pesticide residues using a partially modified multi-residue method for agricultural chemicals by a Varian CP-3800 Gas Chromatograph equipped with a pulse flame photometric detector (PFPD) and 63Ni electron capture detector (ECD), respectively. The study revealed the presence of three organophosphorus pesticide residues namely; chlorpyrifos (0.04 mg/kg), pirimiphos-methyl (0.03 mg/kg) and diazinon (0.01 mg/kg), with chlorpyrifos occurring most frequently, and six synthetic pyrethroid pesticide residues namely; allethrin (0.01 mg/kg), lambda-cyhalothrin (0.03 mg/kg), deltamethrin (0.03 mg/kg), cypermethrin (0.04 mg/kg), bifenthrin (0.02 mg/kg) and permethrin (0.02 mg/kg), with cypermethrin occurring most frequently. None of the detected pesticides’ average residues did exceed their European Union Maximum Residue Limits for cocoa beans. Considering levels of pesticide residues in the fermented dried cocoa beans analysed against the European (EU) commissions’ regulations on pesticides residues, cocoa beans from the study area will not pose any significant threat to the cocoa industry in Ghana as far as shipment to Europe is concern. The presence of organophosphorus and synthetic pyrethroid pesticide residues in the cocoa bean samples analysed could be attributed to their usage by cocoa farmers in the study area. The routine monitoring of pesticide residues in the study area is necessary for the prevention, control and reduction of environmental pollution, so as to minimize health risks.

Synthetic Pyrethroids Pesticide Residues in Soils and Drinking Water Sources from Cocoa Farms in Ghana

The contamination of pesticides in 32 soils and 64 drinking water samples was investigated from cocoa farms in the Dormaa West District of Ghana to assess pollution status. A total of nine synthetic pyrethroids pesticides were measured with a high resolution Varian CP-3800 Gas Chromatograph equipped with <sup>63</sup>Ni electron capture detector (ECD). Eight synthetic pyrethroid residues namely fenvalerate, deltamethrin, cypermethrin, bifenthrin, permethrin, lambda-cyhalothrin, allethrin and cyfluthrin were detected with lambda-cyhalothrin and allethrin occurring most frequently in soil and water respectively. The concentrations of synthetic pyrethroids residues in the soil samples were in the ranges of; 0.02-0.03 mg/kg for lambda-cyhalothrin, 0.010-0.02 mg/kg for allethrin, 0.010-0.04 mg/kg for cyfluthrin, <0.01-0.04 mg/kg for cypermethrin, 0.02-0.06 mg/kg for deltamethrin, and <0.01-0.03 mg/kg for bifenthrin. Similarly, the synthetic pyrethroids residues in the water samples were in the ranges of; 0.01-0.05 µg/L for allethrin, 0.01-0.04 µg/L for fenvalerate, 0.01-0.04 µg/L for cypermethrin and 0.01-0.05 µg/L for deltamethrin. The concentrations of synthetic pyrethroids pesticide residues recorded in the soil samples analysed were generally below and within their respective US MRLs for agricultural soils, except the mean concentration values recorded for pesticides such as lambda-cyhalothrin at Diabaa (S2) and Krakrom (S3), allethrin at Diabaa (S2) and deltamethrin at Kwakuanya (S4), which were above their respective US MRLs for agricultural soils. The trends of synthetic pyrethroids pesticide residues in the water samples analysed from the various distances to cocoa farms decreased with an increase of water source to cocoa farm (ranking; 0-15m>16-30m>above 30m). All synthetic pyrethroids pesticide residues recorded in the water samples were below and within their respective WHO MRLs for drinking water except for deltamethrin, which exceeded the WHO MRL at Kwakuanya (S4) at distance 0-15m from a cocoa farm. The presence of synthetic pyrethroids residues in the soil and water samples analysed is an indication of the use of the pesticide by cocoa farmers in the study area. The routine monitoring of pesticide residues in the study area is necessary for the control and reduction of environmental pollution.

Effect of Organic Production Systems on Quality and Postharvest Performance of Horticultural Produce

Organic standards include a well-defined set of practices and a list of technical tools that are permitted by regulation. Organic products are mainly purchased for their safety and absence of synthetic pesticide residues. Furthermore, a diet based on organic products claims to provide health benefits due to the high nutritional value compounds that are more concentrated in organic products compared to conventional ones. As the scientific basis of the differences between organically- and conventionally-grown fruits and vegetables is under debate, some of the published work, together with some recent unpublished results, will be covered in the present review. In addition, the effect of different approaches to organic horticultural production will be described. Many studies have confirmed lower nitrate content, especially in leafy vegetables, and higher antioxidant compounds in organically-grown fruits in comparison to conventional ones. A recent study reported organic kiwifruit as higher in ascorbic acid and total phenol content than conventional kiwifruit. These differences were maintained throughout cold storage. Similarly, in organic grapes, antioxidant-related compounds were significantly higher than in conventionally-grown grapes. Analogous results were obtained with organic strawberries grown in protected conditions. However, conventional products usually result in higher moisture content, and this should be taken into account to confirm the differences on a dry matter basis. Possible explanations for the effects of organic farming practices on nutritional quality and postharvest performance of fresh produce are the following: (i) organic amendments provide a high input of exogenous organic matter and of nutrients for a long period; in contrast, mineral fertilizers, allowed only in conventional farming systems, are highly concentrated in nutrients that are directly available for root uptake in a shorter time period; (ii) the use of synthetic pesticides (only possible in conventional agriculture) slows down defence mechanisms against pathogens, with the consequence of favoring primary metabolism; (iii) cultural practices may result in different plant composition and nutritional quality, which in turn influence cold storage performance of the products as these differences, both in fertility and pest management, affect the allocation of secondary plant metabolites (such as ascorbic acid and phenolic compounds).

Occurrence and spatial distribution of pesticide residues in butter and ghee (clarified butter fat) in Punjab (India).

The present study was undertaken to monitor organochlorine, organophosphate, and synthetic pyrethroid pesticide residues in butter (n = 55) and ghee (n = 56) samples collected from three different regions of Punjab. The estimation of pesticide residues was done by multiple residue analytical technique using gas chromatography equipped with GC-ECD and GC-FTD. The confirmation of residues was done on gas chromatography mass spectrometry in both selective ion monitoring (SIM) and scan mode. Results indicated the presence of hexacholorocyclohexane (HCH) and p,p' DDE as predominant contaminant in both butter and ghee. Residues of HCH were detected in 25 and 23% samples of butter and ghee, respectively, while residues of p,p' DDE were recorded in 29 and 25% of butter and ghee samples, respectively. None of the butter and ghee sample violated the MRL values of 200 ng g(-1) for HCH and 1250 ng g(-1) for dichorodiphenyl tricholorethane (DDT). The presence of endosulfan, cypermethrin, fenvalerate, deltamethrin, and chlorpyrifos were observed in a few butter and ghee samples at traces. The spatial variation for comparative occurrence of pesticide residues indicated higher levels in the south-western region of Punjab. Additionally, the temporal variation indicated the significant reduction of HCH and DDT levels in butter and ghee in Punjab.

Liver Histopathology of Chickens Fed With Aluminium Phosphide-Treated Maize-Based Diets

Pesticides are used in agriculture to protect crops but residues of synthetic pesticides have adversely affected the environment, livestock and man. However, information on toxic effects of these pesticides on livestock in Nigeria is scanty. Therefore, the study was conducted to assess toxicity of insecticides on chickens. Fourteen -week old Nera black hens (n=60) were allotted into three treatments and fed Aluminium phosphide (AlP)-treated maize-based diets. T1 was the control diet. T2, T3, T4 and T5 contained maize grains fumigated with 1.04 g of AlP tablet per 25 kg of maize grains fumigated for 2 weeks, 2.08 g of AlP tablet per 25 kg of maize grains fumigated for 2 weeks, 1.04 g of AlP tablet per 25 kg of maize grains fumigated for 4 weeks, and 2.08 g of AlP tablet per 25 kg of maize grains fumigated for 4 weeks respectively. Each diet was fed for 10 weeks. The study lasted for ten weeks. The experimental design was a completely randomized design. Each treatment had three replicates with 20 birds per treatment. Slide preparation and microscopy of the tissues were carried out at the Department of Clinical Pathology, University of Ibadan, Nigeria. Liver histopathology showed mild, moderate and severe congestion of blood vessels.

Residues of organochlorine and synthetic pyrethroid pesticides in honey, an indicator of ambient environment, a pilot study

Samples of honey were screened to monitor residues of organochlorine and pyrethroid pesticides. The study meant to examine the quality of honey, and to use honey as a bioindicator of environmental contamination. Residue levels were determined by gas chromatography (GC-μECD). Samples had a wide spectrum of organochlorine and synthetic pyrethroids pesticides, with hexachlorobenzene (HCB) as the most frequently detected organochlorine, followed by permethrin, heptachlor epoxide. Only one sample had a concentration of γ-HCH higher than maximum residue limit of honey (0.01mgkg−1). Residues of organochlorines detected, indicate the presence of some fresh supplies, despite the ban imposed on their use. The study confirmed that honey bee and beehive matrices could be used as gauge for monitoring environment contamination. From public health point of view, the observed levels of pesticide residues in honey do not pose a serious health risk to the consumers, but raises questions of the source of organochlorines.

Pesticide residues in fruits and vegetables produced in organic, integrated and conventional systems

Presented research concerns the evaluation of residues of synthetic pesticides in crops, depending on the system of production: conventional, integrated and organic. The study was conducted in 2005-2009 on 1134 samples of plant material derived from the four provinces: Lubelskie, Podlaskie, Warminsko-Mazurskie and Mazowieckie. The 123 active substances of pesticides were searched in the plant material. This research has been shown that in the samples of fruit produced in the integrated system percentage of samples with residues below the maximum residue levels (MRL) is larger (55 %) than in the samples from conventional production (28 %), and less with above MRL (3 %). The pesticide residues were also detected in 8 % in samples of fruits and vegetables from organic production.

Consumers' Perceptions and Willingness to Pay for Organically Grown Vegetables

Vegetable production plays an important role in food security and provides food and raw materials for industries, income from sales, and employment for small households in urban and peri-urban areas in West Africa. However, some significant health hazards may occur due to misuse of chemicals pesticides applied during vegetable production. Reducing health risks by developing alternatives to synthetic pesticides may be beneficial for consumers and producers. This study assesses the potential market for organically grown vegetables and analyzes consumer awareness and perceptions of synthetic pesticide residues in vegetables. Price levels that consumers are willing to pay for chemical-free vegetable products were evaluated. A hedonic-pricing model (preferences choice) was used to identify determinants of consumer willingness to pay for organically grown vegetables. Data were collected with a questionnaire on consumer perceptions of produce quality problems, awareness of pesticide use on vegetables, and willingness to pay for synthetic pesticide free vegetables. Consumers were aware of heavy use of synthetic pesticides on vegetables. Consumer preferences for quality vegetables included damage free, freshness, size, color, and firmness. Consumers were willing to pay a premium of more than 50% for synthetic pesticide-free vegetables. The most likely factors affecting consumer willingness to pay for organically grown vegetables were awareness of chemical residues and health risks, damage free, reliable availability of products, taste, and income level. There is a potential demand for synthetic pesticide-free vegetables.

Opinion: Improved Food Safety Requires Integration of Pest, Plant and Pesticide Interactions

In the real world, there is an interaction between pest, plant and pesticide that greatly affects the kinds and amounts of potentially toxic and allergenic chemicals that we eat. These interactions are virtually ignored in food safety regulation. Exposure to potentially toxic chemicals from crop foods comes from three principle sources: fungal toxin contamination, natural toxicants and allergens of the plant itself (‘self-defense’ chemistries), and from synthetic pesticide residues. To be effective, these ‘self-defense’ chemistries are often potent toxicants. When tested similarly to synthetic pesticides, plant self-defense chemistries are often toxic to genes, cause cancer, cause reproductive problems, cause birth defects, and the like. Our exposure to self-defense chemicals and allergenic proteins of plants is variable, and depends on growing conditions, which kind of crop, which variety of crop, selection for natural resistance to insects and fungi, the plant’s dynamic response to environmental stressors including insects and fungi, and possible mitigation of insect and fungal stress by use of synthetic or biotechnology pesticides, and post-harvest management. The ratio of self-defense chemistries to synthetic pesticides in our diets has been estimated at greater than 10,000 to 1 (Ames, 1983; Beier and Nigg, 2001). Almost the entire focus of society and regulatory agencies is to manage the 1 part in 10000. Obviously, this partitioning of resources is not scientifically rational. The plant world is interactive, and this dynamic must be managed to improve food safety.

Mixtures in the real world: The importance of plant self-defense toxicants, mycotoxins, and the human diet

A perusal of research presented at the Annual Society of Toxicology Meetings, or in nearly any toxicology journal, will show that the overwhelming emphasis of toxicology research is on synthetic chemistries. Because of substantial potency and exposure to natural chemicals, the overwhelming focus on synthetic chemistries cannot lead to a realistic understanding of chemical risk to the general population. Natural chemicals, simply because of their abundance and potency, may be as likely to be a public health concern and to be involved in chemical interactions (natural:natural, natural:pharmaceutical; or natural:synthetic) as are environmental levels of synthetic chemicals. All plants have a mix of natural self-defense chemistries and mycotoxins that, when tested in a manner comparable to synthetic pesticides, cause the entire spectrum of toxic effects. As a further complication, plants also escalate much of their self-defense chemistry when attacked by insects and fungi, and damaged crops often have higher mycotoxins levels. Effective crop protection will typically reduce the plant's levels of self-defense toxicants and mycotoxins, but may add residues of synthetic pesticides or add some other risk variable. In addition, cooking may also alter the food chemistry (e.g., acrylamide). The mixtures toxicologist needs to address the real world mixture of natural and synthetic chemicals. Public policy on crop-food safety cannot be sensibly guided without these data and large voids in our understanding of risks from real-world mixtures cannot be in the public interest.

Toxicity and Repellency of Hot Pepper Extracts to Spider Mite, Tetranychus urticae Koch

Increasing concern about persistence and environmental impact of synthetic pesticide residues require development of biodegradable and environmentally safe alternatives. The potential of using fruit extracts of hot pepper as alternatives to synthetic acaricides for controlling the two-spotted spider mite, Tetranychus urticae Koch, is explored in this study. Twenty-four Capsicum accessions (Solanaceae) were screened for their toxicity and repellency to the spider mites. Crude extracts from fruits of C. chinense, C. frutescens, C. baccatum, C. annuum, and C. pubescens were prepared in methanol and tested for their acaricidal properties. Spider mite mortality was greatest (45%) when fruit extract of accession Grif-9169 (C. annuum) was used. Results from diving board bioassays indicated that mites avoided filter paper strips treated with hot pepper extracts from accessions PI-596057 (C. baccatum), PI-195299 (C. annuum), and Grif- 9270 (C. annuum). This investigation suggests that methanolic extracts of these three accessions may have a great potential for repelling spider mites and should be field-tested on a large-scale to assess their value in managing populations of spider mites, which could reduce reliance on synthetic acaricides. An attempt was made to correlate repellency with chemical constituents of fruit extracts of the most repellent accessions to identify chemical sources of repellency. Capsaicin and dihydrocapsaicin, the pungent components of pepper fruit, were not correlated with toxicity or repellency, indicating that these are not likely related to the toxicity or repellency of the pepper fruit extracts. Other, unidentified chemicals are likely responsible for toxicity and repellency to the two-spotted spider mite

Residues and Half-Lives of Pyrethrins on Field-Grown Pepper and Tomato

The dried flower heads of Tanacetum cinerariifolium Trev. (Family: Compositae) contain insecticidal compounds collectively called “pyrethrins.” Pyrethrins are the subject of intense interest for use in crop protection because their toxicological properties permit control of certain insect species at application rates as low as 5–10 g AI acre−1. Seedlings of sweet pepper, Capsicum annuum L. cv. Bell Boy Hybrid and tomato, Lycopersicon esculentum Mill. cv. Mountain Spring F1 Hybrid were planted and sprayed with a Multi-Purpose Insecticide formulation that contains 0.2% pyrethrins, 1.0% piperonyl butoxide (PBO), 88% diatomaceous earth, and 10.8% inert ingredients. The formulation was sprayed on pepper and tomato foliage when tomato fruits became red ripe and pepper became mature green at the rate of 6 lbs of formulated product per acre (5.4 and 27.2 g AI of pyrethrins and PBO, respectively). Following spraying, pepper and tomato leaves and fruits were collected at different time intervals for residue analysis using a high performance liquid chromatograph (HPLC) equipped with a UV detector. Residues of pyrethrins and PBO were generally higher on the leaves than fruits. Initial deposits (1 h following spraying) of pyrethrins were significantly higher on pepper than tomato fruits. Half-life (T 1/2) values on pepper and tomato fruits did not exceed 2 h. Where concern exists over synthetic pesticide residues on treated crops and in the environment, pyrethrins are suitable alternatives that can be used to reduce the risk of exposure to synthetic pesticide residues.

Residues and Half-Lives of Pyrethrins on Field-Grown Pepper and Tomato

Abstract The dried flower heads of Tanacetum cinerariifolium Trev. (Family: Compositae) contain insecticidal compounds collectively called “pyrethrins.” Pyrethrins are the subject of intense interest for use in crop protection because their toxicological properties permit control of certain insect species at application rates as low as 5–10 g AI acre−1. Seedlings of sweet pepper, Capsicum annuum L. cv. Bell Boy Hybrid and tomato, Lycopersicon esculentum Mill. cv. Mountain Spring F1 Hybrid were planted and sprayed with a Multi-Purpose Insecticide formulation that contains 0.2% pyrethrins, 1.0% piperonyl butoxide (PBO), 88% diatomaceous earth, and 10.8% inert ingredients. The formulation was sprayed on pepper and tomato foliage when tomato fruits became red ripe and pepper became mature green at the rate of 6 lbs of formulated product per acre (5.4 and 27.2 g AI of pyrethrins and PBO, respectively). Following spraying, pepper and tomato leaves and fruits were collected at different time intervals for residue analysis using a high performance liquid chromatograph (HPLC) equipped with a UV detector. Residues of pyrethrins and PBO were generally higher on the leaves than fruits. Initial deposits (1 h following spraying) of pyrethrins were significantly higher on pepper than tomato fruits. Half-life (T 1/2) values on pepper and tomato fruits did not exceed 2 h. Where concern exists over synthetic pesticide residues on treated crops and in the environment, pyrethrins are suitable alternatives that can be used to reduce the risk of exposure to synthetic pesticide residues.

Pesticide residues in food: investigation of disparities in cancer risk estimates.

Much of the public perceives that exposure to synthetic pesticide residues in the diet is a major cause of cancer. The National Research Council (NRC), in a 1987 report, Regulating Pesticides in Food: The Delaney Paradox, evaluated cancer risks for 29 pesticides that are rodent carcinogens and estimated that the risks for 23 were greater than one-in-a-million. In contrast, our group has ranked possible carcinogenic hazards from a variety of human exposures to rodent carcinogens using the HERP (Human Exposure/Rodent Potency) index, and found that dietary residues of synthetic pesticides ranked low. This paper evaluates the disparities in these analyses by examining the two components of risk assessment: carcinogenic potency in rodents and human exposure. Potency estimates based on rodent bioassay data are shown to be similar whether calculated, as in the NRC report, as the regulatory q1* or as TD50. In contrast, estimates of dietary exposure to residues of synthetic pesticides vary enormously, depending on whether they are based on the Theoretical Maximum Residue Contribution (TMRC) calculated by the Environmental Protection Agency vs. the average dietary residues measured by the Food and Drug Administration in the Total Diet Study (TDS). The TMRC is the theoretical maximum human exposure anticipated under the most severe field application conditions, which are far greater than dietary residues measured in the TDS. Several independent exposure studies suggest that the FDA dietary residues are reasonable estimates of average human exposures, whereas TMRC values are large overestimates. Using standard methodology and measured dietary residues in the TDS, the estimate of excess cancer risk from average lifetime exposure to synthetic pesticide residues in the diet appears to be less than one-in-a-million for each of the ten pesticides for which adequate data were available.

Heterocyclic amines formed by cooking food: comparison of bioassay results with other chemicals in the Carcinogenic Potency Database.

Results in the Carcinogenic Potency Database (CPDB) on 11 mutagenic heterocyclic amines (HA) tested for carcinogenicity in rats, mice and cynomolgus monkeys are compared to results for other chemicals. An analysis of strength of evidence of carcinogenicity for HA vs. other mutagenic carcinogens and vs. all rodent carcinogens, indicates strong carcinogenicity of HA in terms of positivity rates and multiplicity of target sites. The liver is the most frequent target site in each species. Despite several target sites in each species, concordance in target sites between rats and mice is restricted to the liver for each HA except one. In cynomolgus monkeys, liver tumors have been induced rapidly by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Human exposures to HA in cooked animal foods are small, in the low ppb range. A comparison of possible carcinogenic hazards from a variety of exposures to rodent carcinogens in the American diet is presented, using an index (Human Exposure/Rodent Potency, HERP) that relates human exposure to carcinogenic potency in rodents. Results indicate that there is a large background of exposures to naturally-occurring rodent carcinogens in typical portions of common foods, and that possible hazards from HA rank below those of most natural pesticides and products of cooking or food preparation; synthetic pesticide residues also rank low.

PUBLIC RISK PERCEPTIONS

One of the major misconceptions in contemporary society is the widespread belief that our food supply is unsafe. The public's perception of risk is quite different than scientific assessment of risk. While scientists see microbial contamination as the key issue (100 to 10,000X greater risk than from exposure to pesticide residues), consumers appear to be most concerned about the effects of synthetic pesticides and fertilizers in the food they buy. Consumers equate “synthetic” with harmful or bad and “natural” with safe or good, yet they ignore the fact that 99.9% of all pesticides humans are exposed to are naturally occurring. Americans eat approximately 1.5 g. of natural pesticides per person per day, or about 10,000 times more than synthetic pesticide residues. Although few plant toxins have been tested for carcinogenicity so far, of those tested about half are rodent carcinogens. Contrary to public perception, environmental pollution accounts for only 2% of all cancers. By contrast, smoking, diet and other personal lifestyle choices account for more than 75%.

Use of low-purity solvents and reagents for analysis of residues of synthetic pyrethroid pesticides by gas chromatography with electron-capture detection

As most of the impurities commonly encountered in solvents and reagents elute from a gas chromatographic column at retention times much smaller then those of synthetic pyrethroids, inexpensive laboratory-grade solvents and reagents can be acceptable for the determination of residues of these pesticides. However, before analysis of the samples, it is desirable to check the suitability of such solvents and reagents by running reagent blanks.

Dietary pesticides (99.99% all natural).

The toxicological significance of exposures to synthetic chemicals is examined in the context of exposures to naturally occurring chemicals. We calculate that 99.99% (by weight) of the pesticides in the American diet are chemicals that plants produce to defend themselves. Only 52 natural pesticides have been tested in high-dose animal cancer tests, and about half (27) are rodent carcinogens; these 27 are shown to be present in many common foods. We conclude that natural and synthetic chemicals are equally likely to be positive in animal cancer tests. We also conclude that at the low doses of most human exposures the comparative hazards of synthetic pesticide residues are insignificant.

Determination of multi-pesticide residues in cereals, cereal products and animal feed using gel-permeation chromatography

Residues of organophosphorus, organochlorine and synthetic pyrethroid pesticides and insect growth regulators were determined in cereals and cereal products. Samples were extracted with acetone-methanol and the extracts cleaned-up by gel-permeation chromatography. The mean recoveries were: 99%, organophosphorus; 94%, organochlorine; 99%, synthetic pyrethroid; and 99%, insect growth regulators.

Multi-residue determination of organochlorine, organophosphorus and synthetic pyrethroid pesticides in grain by gas-liquid and high-performance liquid chromatography.

A multi-residue method for the determination of organochlorine, organophosphorus and synthetic pyrethroid pesticides and carbaryl in grain is presented. After extraction with acetone-methanol, the pesticides are separated from co-extractives by a partition process with dichloromethane and chromatography on an acidic aluminium oxide column. Quantitative determinations are made by packed column gas-liquid chromatography using an electron-capture detector for the organochlorine pesticides and a flame-photometric detector for the organophosphorus pesticides. High-performance liquid chromatography using an ultraviolet spectrophotometric detector is used for the determination of synthetic pyrethroids and carbaryl. Capillary column gas-liquid chromatography is used for confirmation of identity of suspected residues of organochlorine, organophosphorus and synthetic pyrethroid pesticides.