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PubMedDate not supplied

Organophosphorus pesticides: do they all have the same mechanism of toxicity?

Organophosphorus (OP) pesticides are used extensively to control agricultural, household and structural pests. These pesticides constitute a diverse group of chemical structures exhibiting a wide range of physicochemical properties, with their primary toxicological action arising from inhibition of the enzyme acetylcholinesterase (AChE, EC 3.1.1.7). Historically, risk characterizations for these toxicants have been based on hazard and exposure data pertaining to individual chemicals. The Food Quality Protection Act of 1996 now requires, however, that combined risk assessments be performed with pesticides having a common mechanism of toxicity. It is therefore critical to consider whether OP pesticides all exert toxicity through a common mechanism. This brief review evaluates the comparative toxicity of the 38 OP AChE inhibitors currently registered for use as pesticides in the United States and examines the data which suggest that some OP pesticides have toxicologically relevant sites of action in addition to AChE. It is concluded that all OP anticholinesterases potentially have a mechanism of toxicity in common, that is, phosphorylation of AChE causing accumulation of acetylcholine, overstimulation of cholinergic receptors, and consequent clinical signs of cholinergic toxicity. Additional macromolecular targets for some OP pesticides, however, may alter the cascade of events following AChE phosphorylation and thereby modify that common mechanism. Furthermore, other macromolecular targets of some OP pesticides appear capable of altering noncholinergic neurochemical processes. These additional actions may contribute to qualitative and quantitative differences in toxicity sometimes noted in the presence of similar levels of AChE inhibition induced by different OP pesticides. Further investigation of these additional sites of action may allow subclassification and influence the decision to perform combined risk assessments on this class of pesticides based on common mechanism of toxicity.

Acetylcholinesterase↗
PubMed2003

Sources of exposure to and public health implications of organophosphate pesticides.

OBJECTIVE: To review the public health significance of organophosphate pesticide exposure in the United States of America. Since the situation of high organophosphate pesticide exposure and the concomitant health risks in the developing countries of the world is well known, this article seeks to highlight the public health significance of organophosphate exposure in the United States, where it is less common than in many other nations. Looking at the situation in the United States would serve to further emphasize the seriousness of organophosphate pesticide-related health issues in developing countries. METHODS: A search for journal articles on organophosphate pesticides and organophosphate exposure was done on the PubMed electronic bibliographic database system of the National Library of Medicine of the United States. To supplement that search, information on organophosphate toxicity, biological monitoring, and regulation of pesticides was obtained from other published articles, textbooks, and relevant Internet sites. RESULTS: Organophosphate pesticides are a group of chemicals that are mainly used in agriculture. Organophosphates inhibit the activity of both the cholinesterase (ChE) enzymes-red blood cell (RBC) ChE and serum ChE-resulting in the cholinergic features of organophosphate toxicity. A 50% reduction in serum ChE activity from the baseline is an indication of acute organophosphate toxicity. The RBC ChE activity, which is less rapidly depressed than the serum ChE activity, is a measure of chronic exposure to organophosphates. Exposures to organophosphates are broadly classified into two categories: occupational and environmental. Occupational exposures occur among agricultural workers (including migrant farmworkers), industrial workers, pest control exterminators, and other workers. Nonoccupational exposure affects a large segment of the general population in the United States. Residential exposures come from organophosphate pesticide use by exterminators and by household residents as well as from dietary and accidental exposures. Other environmental exposures occur in public places and areas close to farms, and exposures could also happen from organophosphate use in chemical warfare or terrorism. In the United States some organophosphate pesticides are restricted by the Environmental Protection Agency in order to protect humans, animals, and the environment. In addition, the Food Quality Protection Act regulates dietary exposure to pesticides, particularly for infants and children. CONCLUSIONS: Organophosphate pesticides continue to pose a risk to human health in the United States. Biological monitoring should be used to strictly regulate occupational exposures to organophosphates and thus protect the health and safety of workers. Among the public there should be an increased awareness of environmental exposure to organophosphates as well as of the threat of chemical warfare or terrorism.

Cholinesterases↗
PubMed1993

Decontaminating pesticide protective clothing.

The review of recent work on the mechanisms of soil removal from textiles assists in understanding decontamination of pesticide protective clothing. The current work provides explanatory conclusions about residue retention as a basis of making recommendations for the most effective decontamination procedures. A caution about generalizations: Some pesticides produce very idiosyncratic responses to decontamination. An example is the paraquat/salt response. Other pesticides exhibit noticeable and unique responses to a highly alkaline medium (carbaryl), or to bleach (chlorpyrifos), or are quickly volatilized (methyl parathion). Responses such as these do not apply to other pesticides undergoing decontamination. Given this caution, there are soil, substrate, and solvent responses that do maximize residue removal. Residue removal is less complete as the concentration of pesticide increases. The concentration of pesticide in fabric builds with successive exposures, and the more concentrated the pesticide, the more difficult the removal. Use a prewash product and/or presoak. The surfactant and/or solvent in a prewash product is a booster in residue removal. Residues transfer from contaminated clothing to other clothing during the washing cycle. Use a full washer of water for a limited number of garments to increase residue removal. The hotter the washing temperature, the better. Generally, this means a water temperature of at least 49 degrees C, and preferably 60 degrees C. Select the detergent shown to be more effective for the formulation: heavy-duty liquid detergents for emulsifiable concentrate formulations and powdered phosphate detergents for wettable powder formulations. If the fabric has a soil-repellent finish, use 1.25 times the amount recommended on the detergent label. For water hardness above 300 ppm, an additional amount of powdered phosphate detergent is needed to obtain the same level of residue removal as obtained with the heavy-duty liquid detergent when laundering fabrics with the soil-repellent finish. The mechanical action of agitation increases dislodgement of particulate material. Too many items in the washing apparatus or too low water volume, or both, decrease agitation and soil removal. Bleach can be used if desired. Fabric softener does not affect pesticide absorption or residue removal in laundering. Dry cleaning is not recommended because the solvents used in dry cleaning may be recycled through dilution, filtration, activated charcoal adsorption, or distillation. Pesticides still may be present in recycled solvents and can be transferred from one item to another, or from one load to subsequent loads of dry cleaning.

Decontamination↗
PubMed2005

Allium cepa derived EROD as a potential biomarker for the presence of certain pesticides in water.

Allium cepa root length inhibition test is a well recommended bioassay for the evaluation of the toxicity of various polluted waters. The utility of EROD (7-ethoxy resorufin O-deethylase) as a potential biomarker of pesticide pollution was investigated using the Allium cepa system. Onion bulbs exposed to model water samples containing any of the six pesticides viz. 2,4-D, HCB, malathion, carbaryl, DDT and endosulphan were analyzed for EROD activity. The pesticide treatment resulted in the enhanced activity of the enzyme, with carbaryl and HCB causing 63- and 53-fold induction respectively with respect to the control at a dose of 1.2 ppb. The industrial wastewater samples from Ghaziabad city of Northern India resulted in about a 68-fold rise in the EROD activity, whereas the Aligarh samples did not exhibit any change within the statistical limit. These results suggest the presence of the test pesticides in the Ghaziabad sample and their absence in the Aligarh sample. Pesticide analysis in the test water samples by HPLC supported this to a large extent. Presence of cycloheximide in the test system brought down the EROD activity, equal to that of control, suggesting the de novo synthesis of the enzyme following the exposure of Allium cepa to pesticides. These studies suggest that the Allium cepa derived EROD can act as a potential biomarker of certain pesticides since even 1ppb of total/individual pesticides brought about >10-fold induction of EROD. We recommend the assay of EROD in the Allium cepa system as a presumptive test for the detection of these pesticides before using analytical techniques like HPLC.

Biomarkers↗
PubMed2006

Pesticides and their metabolites in the homes and urine of farmworker children living in the Salinas Valley, CA.

In support of planning efforts for the National Children's Study, we conducted a study to test field methods for characterizing pesticide exposures to 20 farmworker children aged 5-27 months old living in the Salinas Valley of Monterey County, California. We tested methods for collecting house dust, indoor and outdoor air, dislodgeable residues from surfaces and toys, residues on clothing (sock and union suits), food, as well as spot and overnight diaper urine samples. We measured 29 common agricultural and home use pesticides in multiple exposure media samples. A subset of organophosphorus (OP), organochlorine (OC) and pyrethroid pesticides were measured in food. We also analyzed urine samples for OP pesticide metabolites. Finally, we administered four field-based exposure assessment instruments: a questionnaire; food diary; home inspection; and a self-administered child activity timeline. Pesticides were detected more frequently in house dust, surface wipes, and clothing than other media, with chlorpyrifos, diazinon, chlorthal-dimethyl, and cis- and trans-permethrin detected in 90% to 100% of samples. Levels of four of these five pesticides were positively correlated among the house dust, sock, and union suit samples (Spearman's rho=0.18-0.76). Pesticide loading on socks and union suits was higher for the group of 10 toddlers compared to the 10 younger crawling children. Several OP pesticides, as well as 4,4'-DDE, atrazine, and dieldrin were detected in the food samples. The child activity timeline, a novel, low-literacy instrument based on pictures, was successfully used by our participants. Future uses of these data include the development of pesticide exposure models and risk assessment.

Agriculture↗
PubMed2002

Effects of addition of straw, chitin and manure to new or recycled biofilters on their pesticides retention and degradation properties.

Pollution of surface and groundwater by pesticides is an increasing problem that needs to be addressed by the authorities as well as by the farmers themselves. Nowadays, some researchers are considering the numerous small spillages at the farm sites as a relevant entry route to be taken into account for predicting surface and groundwater pollution. In order to tackle this problem, several solutions exist for limiting the disposal of pesticide wastes into the environment. One such system is biopurification of farm wastes by biobed, biofilter or phytobac. In this study, the results of pesticides retention by biofilters under outdoor conditions are presented. The biofilters were filled with a mixture of a soil + peat constituent (25% by volume for each of them) and the rest (50%) with straw or with composted manure ot with chitin (in this later case at the rate of 5 g chitin per liter of substrate). The soil + peat constituent was made either of a material already challenged by pesticides (= recycled biofilters) or of untreated material (new biofilters). Selected pesticides (atrazine, carbofuran, chloridazon, chlortoluron, cyanazine, isoproturon and lenacil) were applied onto biofilters and the eluates were collected and analyzed. Two successive injections of pesticides into the biofilters were conducted. After the first pesticides application, the recycled biofilters made of soil + peat previously treated with pesticides had better retention and degradation rates than the new biofilters. Adding manure also improved these properties of biofilters. Columns made of unchallenged soil + peat and straw (new biofilters) were the least satisfactory: up to 25% of carbofuran were lost. Biofilters made of unchallenged soil + peat and chitin retained the least lenacil. Atrazine was the most retained by biofilters (either new or recycled) with added chitin. Cyanazine was almost absent in the percolates of all biofilters. After the second application of carbofuran and isoproturon, all biofilters improved to the point where (with the exception the new biofilters made of chitin) they retained the totality of the pesticides.

Biodegradation, Environmental↗
PubMed1996

An estimate of the incidence of pesticide poisoning in Hong Kong.

The exact incidence of vegetable-borne and other types of acute pesticide poisoning among the 6.2 million population of Hong Kong is difficult to determine. Vegetable-borne pesticide poisoning is notifiable and, in 1992, 47 outbreaks of such poisoning (all caused by methamidophos) affected about 329 persons. No similar figures are available for non-vegetable-borne pesticide poisoning, but we calculated it based on our experience at the Prince of Wales Hospital (PWH) and on reports to our territory-wide Drug and Poisons Information Bureau (DPIB). The PWH serves the 1.2 million population in the New Territories East, where much of the remaining farmland in Hong Kong is situated. Extrapolating from our regional data to the whole of Hong Kong, we estimate that, in subjects aged > or = 15 y between 1988 and 1991, the annual incidence of non-vegetable-borne acute pesticide poisoning from parasuicides, non-farming accidents and work-related accidents was 59, 4 and 1, respectively. Between 1988 and 1992, 5 pediatric cases of non-vegetable-borne pesticide poisoning were reported to the DPIB annually. In the New Territories East, 80% of the acute pesticide poisoning deaths were due to 24% paraquat solution. In Hong Kong, acute pesticide poisoning is relatively uncommon. By maintaining a close surveillance of imported vegetables for excessive methamidophos residues, replacing high concentration paraquat with less toxic formulations, and placing pesticides out of reach of children, much of this morbidity and mortality associated with acute pesticide poisoning can be prevented.

Adolescent↗
PubMed1990

Pesticide loss to the atmosphere.

Pesticides may be transformed by chemical and biological processes or transported from the site of application by several processes including runoff, movement through the soil to ground water, volatilization, transport on soil particles, and wind erosion. Contamination of water by pesticide residues is a matter of concern as is contamination of the earth's atmosphere. The form in which a pesticide enters the air and the dimensions of pesticide-containing particulate matter affect movement and deposition. Local transport over distances of several miles may be responsible for adverse effects on nontarget species. Effects of long-range transport are more difficult to assess, but pesticides increase the burden of organic chemicals in the atmosphere. Field measurements of pesticide volatilization and deposition of residues in rainfall, particulate matter, fog, etc., provide information on the relative importance of these processes. Adequate information concerning chemical reactions of pesticides in air is lacking. Because it is desirable to minimize low-level human and environmental exposure resulting from airborne pesticide residues, potential for losses to the air should be taken into account in selecting pesticide formulations and application methods.

Agriculture↗
PubMed2006

Ambient air concentrations of pesticides used in potato cultivation in Prince Edward Island, Canada.

Ambient air concentrations of nine selected pesticides used in potato cultivation were investigated on Prince Edward Island by collecting samples during the summer of 1998 at three potato farm sites and one non-agricultural site. In 1999, air samples were collected at a single potato farm site during local application of pesticides. The fungicide chlorothalonil was the only pesticide detected in every sample in both years, even in samples with a duration as little as 5 h. In 1998, maximum (45-458 ng m(-3)) and mean (22-193 ng m(-3)) concentrations of chlorothalonil from composite 42 h samples were one to two orders of magnitude greater at agricultural sites than at the non-agricultural site (3.9 and 2.5 ng m(-3), respectively). Maximum and mean concentrations of chlorothalonil from combined 24 h samples at the farm site in 1999 were higher than those measured in 1998 (636 and 284 ng m(-3), respectively). The ubiquitous presence in air of relatively high concentrations of chlorothalonil in agricultural areas on Prince Edward Island is likely related to its repeated use on potato farms where fungicides account for 80-90% of pesticides applied. Eight of nine pesticides were detected at farm sites in 1998 and they are ranked by mean concentration from highest to lowest as follows: chlorothalonil, methamidophos, azinphos-methyl, alpha-endosulfan, beta-endosulfan, pirimicarb, metobromuron, metribuzin, metalaxyl and fluazifop-P-butyl. Concentrations of metalaxyl, pirimicarb, metobromuron and fluazifop-P-butyl in air are among the first reported values for these pesticides. Five pesticides were detected at the Summerside farm in 1999, but only two fungicides (chlorothalonil and metalaxyl) were used locally, while the presence of metribuzin, alpha-endosulfan and methamidophos in air was not associated with local application. Evidence of pesticide drift was observed for chlorothalonil, alpha-endosulfan and methamidophos, and these pesticides were identified as being of high concern in terms of potential wildlife exposure on the Island.

Agriculture↗
PubMed2003

Pesticide degradation in a 'biobed' composting substrate.

Pesticides play an important role in the success of modern farming and food production. However, the release of pesticides to the environment arising from non-approved use, poor practice, illegal operations or misuse is increasingly recognised as contributing to water contamination. Biobeds appear to offer a cost-effective method for treating pesticide-contaminated waste. This study was performed to determine whether biobeds can degrade relatively complex pesticide mixtures when applied repeatedly. A pesticide mixture containing isoproturon, pendimethalin, chlorpyrifos, chlorothalonil, epoxiconazole and dimethoate was incubated in biomix and topsoil at concentrations to simulate pesticide disposal. Although the data suggest that interactions between pesticides are possible, the effects were of less significance in biomix than in topsoil. The same mixture was applied on three occasions at 30-day intervals. Degradation was significantly quicker in biomix than in topsoil. The rate of degradation, however, decreased with each additional treatment, possibly due to the toxicity of the pesticide mixture to the microbial community. Incubations with chlorothalonil and pendimethalin carried out in sterile and non-sterile biomix indicated that degradation, rather than irreversible adsorption to the matrix, was the main mechanism responsible for the reduction in recovered residues. Results from these experiments suggest that biobeds offer a viable means of treating pesticide waste.

Biodegradation, Environmental↗
PubMed2004

Understanding the tropospheric transport and fate of agricultural pesticides.

Many field monitoring studies have indicated the substantial role of the troposphere as both a sink and transport medium for pesticides. At the same time, this is the least studied and understood environmental compartment in regards to pesticide fate. Although the fundamental principles behind volatilization and tropospheric reactivity are well understood, it is becoming increasingly apparent that the ability to quantitatively measure flux and reaction rates in the air will continue to pose problems for researchers. To date, most deterministic models that try to simulate real world conditions generally fail to provide tropospherically relevant flux and reaction rates because it is virtually impossible to scale down all possible interactions occurring in a near-infinite reservoir. Better field methods for determining flux are emerging and more ambient air monitoring studies are being conducted. This growing database of information, together with an understanding of physicochemical properties and use of expert systems, has increased the predictive capability for estimating volatilization flux of pesticides. Unfortunately, there are very limited environmental data on the tropospheric reaction rates of pesticides, and more experimental studies using semivolatile to low-volatility pesticides or their more volatile homologues are required to validate existing structure-activity relationship (SAR) model predictions. The development of new analytical strategies using elevated temperatures for assessing semivolatile to low-volatility pesticide reaction rates and products may provide an alternative approach to the need for controlled environmental temperature data. Recent international workshops organized by the Health Council of The Netherlands for developing uniform approaches for assessing exposure risks to pesticides in air exemplify efforts to synchronize flux with environmental fate information for determining human health and ecological risks. When more detailed pesticide information is desired, especially in high-use agricultural areas, where exposure to humans and nontarget ecological communities is a major concern, field flux measurements and downwind monitoring, together with experimental fate studies, should be considered. The integration of models, empirical testing, and real world monitoring will provide the ultimate safety net needed for assessing exposure risks to airborne pesticides.

Atmosphere↗
PubMed1993

Effects of pesticides on isolated rat hepatocytes, mitochondria, and microsomes.

Twenty-seven pesticides, with which people are concerned, especially as residues in food, were examined in vitro for their effects on hepatocytes, mitochondria, and microsomes isolated from male rats. Nineteen pesticides returned non-protein sulfhydryl (NPSH) contents in hepatocytes to less than 80% of control at concentrations from 10(-3) to 10(-5) M after 90 min incubation. Among them, only dichlofluanid was reactive with glutathione non-enzymatically. Lipid peroxidation in hepatocytes was stimulated by five pesticides at 10(-3) M, with edifenphos being the most potent peroxidant. Cell viability was considerably decreased by incubation with chlorobenzilate, edifenphos, dichlofluanid, and chinomethionat at 10(-3) M, and in these cases, depletion of cellular adenosine 5'-triphosphate (ATP) contents proceeded to cell death. With respect to isolated mitochondrial respiration, six pesticides inhibited state 3 and/or state 4 respiration rates at concentrations from 10(-3) to 10(-5) M, whereas three pesticides uncoupled state 4 respiration at 10(-3) M. With respect to isolated microsomal lipid peroxidation, seven pesticides, five of which were organophosphorus compounds, were peroxidative at concentrations from 10(-3) to 10(-5) M, whereas seven pesticides were antioxidative at concentrations from 10(-3) to 10(-7) M. Only three pesticides, aldicarb, maleic hydrazide, and chlormequat chloride had no effect on any parameters tested at 10(-3) M. Pesticides that affected isolated mitochondria or microsomes did not necessarily have any effect on isolated hepatocytes.

Animals↗
PubMed1994

Evaluation of methods for monitoring the potential exposure of small children to pesticides in the residential environment.

A nine-home pilot study was conducted to evaluate monitoring methods in the field that may be used to assess the potential exposures of children aged 6 months to 5 years to pesticides found in the home environment. Several methods, some of which were newly developed in this study, were tested for measuring pesticide residues in indoor air, carpet dust, outdoor soil, and on the children's hands. Information was also collected on household characteristics, pesticides used and stored at the residence, and children's activities. Pesticides were detected at all nine study homes. With the exception of one home, at least one pesticide was detected in all matrices sampled at each house. Of the 30 target pesticides, 23 were detected during the study. The most frequently detected pesticides were chlordane, chlorpyrifos, dieldrin, hepatachlor, and pentachlorophenol. The greatest number of pesticides and highest concentrations were found in carpet dust. The results of these investigations will be discussed in terms of performance of the methods and the distribution of pesticides across the various media sampled.

Child, Preschool↗
PubMed1995

Effects of pesticides on isolated rat hepatocytes, mitochondria, and microsomes II.

Twenty-two pesticides were examined in vitro for their effects on hepatocytes, mitochondria, and microsomes isolated from male rats. Twelve pesticides reduced non-protein sulfhydryl (NPSH) content in hepatocytes to less than 80% of control at a concentration of 10(-3) M. Chlorothalonil and ziram were especially effective, reducing NPSH content at 10(-4) M after 90 min incubation. Among those pesticides, only copper terephthalate and chlorothalonil were reactive with glutathione non-enzymatically and enzymatically, respectively. Lipid peroxidation in hepatocytes was stimulated by four pesticides, namely, chlorothalonil, pretilachlor, ethoprofos, and metribuzin at 10(-3)-10(-4) M. Cell viability was considerably decreased following incubation with chlorothalonil, trichlamide, and ziram. Hepatotoxicity of trichlamide was considered to be associated with its direct adverse effects on mitochondrial energy production, since it uncoupled isolated mitochondrial respiration at 10(-6) M and depleted cellular ATP content prior to cell death. Conversely, chlorothalonil- and ziram-induced hepatotoxicity seemed to be related to their depleting effects on cellular sulfhydryls, since addition of the thiol compound dithiothreitol to the hepatocytes incubation mixture protected cells. With respect to isolated mitochondrial respiration, four pesticides inhibited state 3 and/or state 4 respiration rates at 10(-3)-10(-4) M, whereas seven pesticides uncoupled state 4 respiration at 10(-3)-10(-6) M. With respect to isolated microsomal lipid peroxidation, three pesticides were peroxidative at 10(-3)-10(-4) M, whereas three pesticides were antioxidative at 10(-3)-10(-7) M. Only two pesticides, beta-endosulfan and metalaxyl, had essentially no effects on any parameters tested at 10(-3) M.

Animals↗
PubMed1980

Morbidity and mortality in workers occupationally exposed to pesticides.

Utilizing cause-of-death information and responses to questionnaires addressed to survivors, mortalities and health impairments in a cohort of workers occupationally exposed to pesticides were compared to occurrences in workers not pesticide exposed, over the period 1971-1977. Seventy-two percent of 2,620 pesticide-exposed workers, and 75% of 1,049 "controls", recruited in 1971-73, were accounted for either by returned questionnaire or mortality. Disease incidence rates were studied in relation to broadly defined occupational subclasses, and to serum concentrations of organochlorine pesticides (OCl) measured at the time of recruitment. Death by accidental trauma was unusually frequent among pesticide applicators. Mortalities from cancer and arteriosclerosis were not detectably different from those observed in the controls. Among survivors, dermatitis and skin cancer were unusually common in structural pest-control operators. Internal cancer was no more frequent in the intensively pesticide-exposed workers than in the controls, but it appeared to occur at an unusually high rate in workers characterized as "possibly pesticide-exposed". There were apparent associations between high serum pesticide OCl levels measured in 1971-73 and the subsequent appearance of hypertension, arteriosclerotic cardiovascular disease, and possibly diabetes. This could imply a causal role of any of the pesticidal and other environmental stresses to which these workers were exposed. The limitations of this type of followup study are discussed.

Age Factors↗
PubMed1993

Health effects in man from long-term exposure to pesticides. A review of the 1975-1991 literature.

The scientific literature published over the period 1975-1991 on long-term health effects from prolonged exposure to pesticides has been reviewed, in order to document the state-of-knowledge on the mortality and morbidity of groups of the population exposed to pesticides. Specific aims of the review were to identify (1) which groups of the population have been more broadly surveyed, (2) which adverse effects have been consistently associated with specific pesticide exposures, (3) which are the pesticides of concern and (4) which health effects would require special attention in future research. The literature on acute effects and animal toxicology studies have not been considered at all in this monograph. In the period of interest, 440 papers have been published. Apart from 97 reviews and a small number of case reports, approximately half of the original investigations were of the case-control design (n = 108), while the remaining papers reported results from proportionate mortality (n = 10), cohort (n = 66) or cross-sectional studies (n = 51), carried out on pesticide applicators (n = 48), agricultural workers (n = 26) or people employed in the pesticide manufacturing industry (n = 50). Most of the case-control studies related to cases of cancer from various sites, especially myelolymphoproliferative disorders (MLP) and soft-tissue sarcomas (STS). When compared to the general population total mortality has been found to be consistently lower among pesticide manufacturers as well as among other groups of workers. This observation has been mostly attributed to the 'healthy worker effect' or, in the case of agricultural workers, to the healthier lifestyle of farm families. With the exception of deaths by accidental causes, non-cancer causes of death (mainly represented by cardiovascular diseases), were generally found to be less frequent than expected among manufacturers or users of pesticides, in particular among farmers. No consistent evidence of a global cancer mortality different from that of the general population has been reported among pesticide manufacturers or applicators. On the other hand, the papers examined have been strikingly consistent in reporting a low overall cancer risk among agricultural workers; life-style, clean air, low prevalence of smoking have been hypothesized so as to explain this observation. Numerous studies considered the possible link between exposure to phenoxyherbicides and occurrence of certain types of cancer, especially STS and MLP disorders.(ABSTRACT TRUNCATED AT 400 WORDS)

Humans↗
PubMed2006

Influence of humic substances on the photolysis of aqueous pesticide residues.

The present work investigated the direct and indirect photolysis of pesticide residues (atrazine, imazaquin, iprodione), in aqueous solutions and under UV-visible radiation (280-480nm). Different kinds of humic substances (HS) were added to samples in order to evaluate their behaviour as possible photocatalysts and their effect on the photolysis of pesticides. The fulvic acids were purchased from the International Humic Substances Society, and they were added to samples in concentrations ranging from 1 to 150 mgl(-1). Titanium dioxide was used as the photocatalyst, in concentration ranging from 10 to 150 mgl(-1). Pesticides photolysis were measured by UV-visible absorption spectroscopy and differential pulse polarography with all used pesticides, reaching total degradation after 2h of irradiation, thus indicating a fast direct photolysis. Photocatalysis by TiO(2) could increase the pesticides photolysis rate up to 40%. This effect, however, was not observed for imazaquin photolysis. Again, except for imazaquin, HS presence showed a positive effect in increasing pesticide degradation, but only within specific concentration ranges (below 10mg l(-1) for iprodione and about 30mgl(-1) for atrazine). Above these ranges HS induce a decrease in the pesticides photolysis rate. Spin-trapping measurements by electronic paramagnetic resonance spectroscopy, using the spin-trap DMPO, showed that HS are able to photogenerate hydroxyl radicals, increasing the pesticides molecule degradation. However, the HS also react with the photogenerated hydroxyl radical, influencing the pesticide photolysis, leading to a decrease in the photolysis rate and causing it to be strongly dependent on the nature and concentration of residues in the water to be treated.

Aminoimidazole Carboxamide↗
PubMed2004

Pesticides in shallow groundwater of Bahawalnagar, Muzafargarh, D.G. Khan and Rajan Pur districts of Punjab, Pakistan.

In Pakistan there is little data on environmental contamination of rural water sources by pesticides. This study evaluated pesticide contamination of groundwater in four intensive cotton growing districts. Water samples were collected from 37 rural open wells in the areas of Bahwalnagar, Muzafargarh, D.G. Khan and Rajan Pur districts of Punjab and analysed for eight pesticides which are mostly used. Information on types of pesticide used and distance to nearest pesticide mixing area and application areas was obtained for each site. From the eight pesticides analysed, six pesticides were detected in the water samples. Only cypermethrin and cabosulfan were not detected. The percentage of detection of bifenthrin, lambda-cyhalothrin, carbofuran, endosulfan, methyl parathion and monocrotophos was, respectively 13.5%, 5.4%, 59.4%, 8%, 5.4% and 35.1% in July; 16.2%, 13.55%, 43.2%, 8%, N.D. (not detected) and 24.3% in October. Maximum contamination levels (MCLs) established by the U.S. Environmental Protection Agency for drinking water were not exceeded. The study has shown the need for monitoring pesticide contamination in rural water resources, and the development of drinking water quality standards for specific pesticides in Pakistan. The conclusions and recommendations will be disseminated to senior decision makers in central and local governments, extension agents and farmers.

Agriculture↗