Organophosphate Residues Research Articles

Reflectometric Cutinase Assay for Rapid Screening of Contaminants and Residues of Insecticidal Organophosphates and Carbamates

Because of the extensive use of insecticides in agriculture, there is an increasing demand for rapid analytical methods for residues in food and feed control. To meet this need, a completely new application of the reflectometric lipase test (Reflectoquant, Merck) was developed. By using the cutinase-induced reaction of the substrate 5-bromo-4-chloro-3-indoxyl caprylate on the test strips, residues of organophosphates and carbamates can be determined on the basis of enzyme inhibition in a fast and inexpensive way. With this technique, we investigated the inhibition effects of representative insecticides, i.e., chlorpyrifos oxon, paraoxon, and carbaryl. The bimolecular inhibitory rate constants (ki) were found to agree well with those obtained by a previously described spectrophotometric cutinase assay in the microtiter-plate format. Recoveries determined with the strip test from spiked samples compared well with those obtained by both the cutinase microtiter-plate assay and liquid chromatographylmass spectrometry.

Pesticide Residues in Honey Samples from Himachal Pradesh (India)

Honey, being a natural product manufactured by honey bees is considered to be free from any extraneous material. The over-reliance on pesticides caused several environmental problems including pesticide residues in food. This constitutes a potential risk for human health, because of their sub acute and chronic toxicity. Therefore this study was carried out to know the extent of pesticide residue in honey produced in the various parts of Himachal Pradesh. Among different pesticides analysed in honey; HCH and its isomers were the most frequently detected followed by DDT and its isomers. Of the studied synthetic pyrethroids, only cypermethrin was found in honey samples. Residues of organophosphates viz. acephate, chlorpyriphos, ethion and monocrotophos were not detected, however malathion's residue was found exceeding the MRL (5 ppb) proposed by the Ministry of Commerce, Government of India. More over honey from natural vegetation contained lesser residues. It can be concluded that honey from Himachal Pradesh had low pesticide residues.

Better than Eating Worms?: Children’s Dietary Exposure to OP Pesticides

Vol. 116, No. 4 EnvironewsOpen AccessBetter than Eating Worms?: Children’s Dietary Exposure to OP Pesticides Julia R. Barrett Julia R. Barrett Search for more papers by this author Published:1 April 2008https://doi.org/10.1289/ehp.116-a172aAboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit Widespread agricultural use of organophosphate (OP) pesticides frequently leads to low-level exposures in adults and children who eat conventionally grown foods. The frequently used one-time measurement of OP metabolites reveals only short-term exposures, thereby providing little evidence on long-term low-level exposures. A new article presents longitudinal evidence that foods grown in conventional fashion—that is, with the use of pesticides—may be a predominant source of exposure in children [EHP 116:537–542; Lu et al.].The article sprang from the Children’s Pesticide Exposure Study, which focused on two groups of children (3–11 years of age) in the Seattle and Atlanta areas from July 2003 to May 2004. For the present study, the researchers examined 23 children in Seattle (19 of whom completed the study) who normally consumed conventional diets. Parents tracked food consumption during the study and collected urine samples twice daily.During interventions over the course of the study, the children’s conventional diets were replaced with organic diets and the differences in urinary metabolites of OP pesticides were measured. The organic diets substituted conventionally produced grain, fruit, juice, and vegetables with those produced without pesticides; meat and dairy products rarely contain OP pesticides and were not substituted. During the summer and fall 2003 intervention periods (15 and 12 days, respectively), the children consumed their regular diets from days 1 to 3 and organic diets from days 4 to 8. After day 8, the children resumed their regular diets. There was no organic diet intervention during the winter and spring 2004 sampling periods.Urine samples were analyzed for metabolites of malathion, chlorpyrifos, diazinon, coumaphos, and methyl pirimiphos; only chlorpyrifos and malathion metabolites were detected frequently enough for statistical analysis. These metabolite levels fell to nearly or fully nondetectable levels within days of the children beginning an organic diet intervention and rose when the children returned to conventional diets.Given that OP pesticides were reported by parents not to have been used in the home and that urinary metabolites were clearly affected by diet, the researchers conclude that conventionally produced foods were the primary source of OP pesticide exposure for the children in this study. They also attribute higher dietary exposures to imported produce eaten in the winter and spring when domestic produce is not available. This finding is supported by a 2006 Environmental Protection Agency report showing that OP residues on imported produce have risen since 1996 even as residues on domestically grown produce have fallen.The authors caution, however, that their findings do not promote limiting fresh produce or eating only organic items, as it is unknown whether the observed exposures are harmful. Additionally, the study group did not represent the general population. However, the findings do provide a basis for more accurate assessment of exposure and associated efforts to determine the effects of OP pesticides on children’s health.For some families, food is likely the primary source of pesticide exposureFiguresReferencesRelatedDetails Vol. 116, No. 4 April 2008Metrics About Article Metrics Publication History Originally published1 April 2008Published in print1 April 2008 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Fetal effects of environmental exposure of pregnant women to organophosphorus compounds in a rural farming community in Sri Lanka

Background. The possible deleterious effects of low-grade, chronic environmental and occupational exposure to organophosphorus compounds (OPCs) are not well documented. Objective. To investigate the possible effects of low-level, chronic exposure of pregnant mothers to OPCs on the fetus by measuring OPC levels, and using markers of OPC exposure, oxidative stress and oxidative tissue damage. Methods. Toxicity was assessed by measuring (i) OPC levels in breast milk and plasma from maternal and cord blood using gas chromatography, (ii) maternal and fetal butyrylcholinesterase (BChE) activity using inhibition assays, (iii) antioxidant status of the fetus using superoxide dismutase activity assays, (iv) oxidative stress in the fetus by determining malondialdehyde (MDA) concentrations, and (v) examining for fetal DNA fragmentation using electrophoresis. Samples were obtained from consenting mothers living in a farming community in southern Sri Lanka at the end of the pesticide spray season (study group) and just before the commencement of the spray season (in-between spray season; control group). Results. Organophosphate residues were detected in only two subjects (chlorpyrifos in maternal and cord blood of one during the spray season and dimethoate in breast milk of another during the in between spray season), but the test employed was capable of only detecting concentrations above 0.05mg/l. However, cord blood obtained during the spray season showed significant inhibition of BChE activity, increased oxidative stress and more DNA fragmentation when compared with cord blood obtained during the in-between spray season. Conclusions. Inhibition of cord blood BChE activity indicates fetal exposure to organophosphorus compounds during times when there is a high probability of environmental drift. This provides a plausible explanation for the increased oxidative stress and high DNA fragmentation in the fetus. Long-term outcomes of such exposures are unknown.

Organochlorine and organophosphate pesticide residues in wheat varieties from Serbia

A survey was carried out to assess the levels of 20 organochlorine and 15 organophosphate pesticides in wheat grown in two regions of the Vojvodina Province in Serbia. A total of 49 samples of seven wheat varieties were collected during the 2004 harvest. In addition, a composite sample of cultivated wheat varieties was prepared from 36 samples coming from the same regions harvested in 2003 for comparison. Official method of analysis AOAC 970.52 was applied for the determination of pesticide residues. The ranges of mean values for organochlorine residues were 32–47 ng g–1 for β-HCH; 28–41 ng g–1 for γ-HCH; <1–61 ng g–1 for aldrin; 5–132 ng g–1 for dieldrin; 15–111 ng g–1 for endrin ketone; and <1–77 ng g–1 for endrin aldehyde. For organophosphate residues the ranges were: 7–27 ng g–1 for thionazin; <5–35 ng g–1 for disulphoton; 42–79 ng g–1 for parathion methyl; 422–1336 ng g–1 for chlorpyriphos; and <5–281 ng g–1 for parathion. The mean levels of residues were compared with the regulated maximum levels according to the European Commission and Serbian national regulation, and the average intake of residues from wheat-based products was estimated for the Serbian population.

Residues of organophosphorus pesticides in different food commodities in Slovenia, 1997 1998

During the period 1997?1998, a total of 1237 samples of different food commodities were analysed for residues of organophosphorus pesticides in Slovenia. The domestic and imported commodities tested included fruits, vegetables, cereals, alcoholic drinks and food of animal origin such as liver, fish, eggs, milk and honey. Residues of organophosphates were detected in 8.2% of samples (101 samples). Violation rate was 0.5% (6 samples). The most frequently found were pirimiphos-methyl in samples of cereals and wheat flour, chlorpyrifos in imported grape and phosalone in apples. No residues of organophosphates were found in food of animal origin.

Neuropathology of organophosphate poisoning in dairy cattle

The purpose of this study is to investigate pathological changes in brain tissues of Frisien Holstein dairy cattle affected by organophosphate (OP). The study was directed to anticipate spongiform encephalopathy. Samples consisted of animal feeds, sera and brain tissues were collected from Lembang, West Java. Animal feeds (fodders and commercial feed) were collected directly from the dairy farms around Lembang. Sera (31 samples) were from dairy cattle owned by the local farmers and brain tissues were from the local animal slaughter house. Pesticide residues were analysed following a standard procedure using gas chromatography (GC). There was an interaction between pesticide residues in animal feeds, residue level of pesticides in sera and brain tissues to cause encephalopathy in dairy cattle. Pesticide contamination in animal feeds was regarded as the source of encephalopathy in dairy cattle. The total average of OP residues (16.8 ppb) were lower than organochlorines/OC (18.7 ppb) in fodder, showing that pesticides were originated from the contaminated soils. On the other hand, the total average of OP residues in commercial feeds (12.0 ppb), sera (85.6 ppb) and brain tissues (22.7 ppb) were higher than OC (1.8; 16.7; and 5.1 ppb). The OP appears more frequently used for dairy farm activity as insecticides. Histopathological examination for brain tissues of dairy cattle showed that most cattle were diagnosed as encephalopathy with microscopic changes of vacuolation, neuronal necrosis, chromatolysis of neurons and nucleolysis of neurons. The encephalopathy was confirmed in rats intoxicated with chlorpyrifos methyl as severe brain damage with spongiform-like lesions. Key Words: Encephalopathy, Organophosphates, Cattle

Effects of processing on pesticide residues in peaches intended for baby food

Peaches containing added residues of chlorpyrifos-methyl, fenitrothion, procymidone and vinclozolin were used for simulated industrial processing in the manufacture of baby food puree. Residues were determined in raw material, in intermediate products at crucial steps of the processing procedure and in final products. Determination of residues was performed by an analytical method, distinguished by high sensitivity, based on acetone extraction, a two-step clean-up/pre-concentration on graphitized carbon and SAX/PSA sorbent, and GC-ECD. The results of the study were interpreted with respect to enforcement of the stringent Maximum Residue Limit (MRL) of 0.01 mg kg−1 established by the European Commission (EC) for any pesticide in baby food. Peeling was identified as the most effective procedure in reducing residues. Thermal treatment (concentration and sterilisation) substantially reduced organophosphate (chlorpyrifos-methyl, fenitrothion) residues, whereas procymidone and vinclozolin residue levels were increased in peach puree.

Biological monitoring of exposure to organophosphate pesticides in children living in peri-urban areas of the Province of Quebec, Canada

This study was undertaken to assess the exposure to organophosphate (OP) pesticides in children from peri-urban areas of the Province of Quebec, Canada, through measurements of semi-specific alkylphosphate (AP) metabolites. Eighty-nine children aged between 3 and 7 years were recruited via pamphlets sent to day-care centers. A first morning urine void was collected early in the spring of 2003 prior to summertime, which is the usual period of outdoor pesticide use. During summertime, up to five more first morning voids were repeatedly collected, at 72-h intervals, over a 13-day period. The potential determinants of exposure were assessed by a questionnaire at the time of urine collection. Methylphosphate metabolites were detectable in 98.2% of the 442 samples analyzed while ethylphosphates were detected in 86.7% of the samples. The geometric mean concentration (GM) of the total AP metabolites was 61.7 mug/g creatinine (range: 2.7-1967.3 mug/g creatinine). The difference in urinary AP concentrations between samples collected during spring and summer was non-significant (P=0.08). There was also no significant difference in the mean AP concentrations between summer samples of individuals living in municipalities where outdoor pesticide use is or is not restricted (P=0.25). However, the presence of a pet in the house was associated with an increase in AP concentrations during spraying season (P=0.02). Pesticides were seldom used, as reported by the questionnaire. A significant correlation was also observed (P<0.001) between the urinary AP concentrations in samples provided by siblings at the same time period. Mean concentrations of AP were generally higher than those reported in other studies. The observed exposure apparently occurred mainly through the dietary ingestion of OP residues. These data raise questions on the levels of OP residues in Quebec food and the possibility that our participants consumed more fruits and vegetables than those in other studies.

Pesticide residues in brain tissues of dairy cattle in Lembang

The use of pesticides to control plant diseases may cause residual formation in crops, its byproduct and environmental. Furthermore, the use of agriculture byproduct as animal feed may cause poisoning or residual formation in animal products. The purpose of this study is to investigate of pesticide residues in brain tissues of dairy cattle in relation to animal feed as a contamination source. Samples consisted of animal feeds (19 samples of fodder and 6 samples of feed), 31 samples of sera and 25 samples of brain tissues of dairy cattle collected from Lembang, West Java. Feeds and fodders were collected from dairy farms located in Lembang. Sera were directly collected from 31 heads of Frisien Holstein (FH) cattle from the same location, while brain tissues of FH cattle were collected from a local animal slaughtering house. Pesticide residues were analysed using gas chromatography (GC). Both residues of organochlorines and organophosphates were detected from brain tissues with average residue concentration OP was 22.7 ppb and OC was 5.1 ppb and a total residue was 27.8 ppb. The pesticide residues in brain tissues are new information that should be taken into consideration since the Indonesian consumed this tissues as an oval. Although pesticides residue concentration was low, pathological changes were noted microscopically from the brain tissues including extracellular vacuolisation, focal necrosis, haemorrhages, dilatation of basement membrane without cellular infiltration. Both pesticide residues were also detected in sera, where OP (9.0 ppb) was higher than OC (4.9 ppb). These pesticides were also detected in animal feeds consisting fodders and feeds. Residues of OP (12.0 ppb) were higher than OC (1.8 ppb) in feeds, but residues of OP (16.8 ppb) were lower than OC (18.7 ppb) in fodders. Although, pesticide residues in sera and brain tissues were below the maximum residue limits (MRL) of fat, the presence of pesticides in brain tissues should be taken into consideration as their effects in brain lesions. There was a correlation between contaminant found in animal feeds and pesticide residues in sera and brain tissues of dairy cattle. Key Words: Pesticides, Residues, Brain, Dairy Cattle

Monitoring of Butter and Ghee (Clarified Butter Fat) for Pesticidal Contamination from Cotton Belt of Haryana, India

Butter (45) and ghee (55) samples were collected from rural and urban areas of cotton growing belt of Haryana and analysed for detecting the residues of organochlorine, synthetic pyrethroid and organophosphate insecticides. The estimation was carried out by using multi residue analytical technique employing GC-ECD and GC-NPD systems equipped with capillary columns. Butter samples were comparatively more contaminated (97%) than ghee (94%), showing more contamination with organochlorine insecticides from urban samples. About 11% samples of butter showed endosulfan residues above MRL value and 2% samples had residues of synthetic pyrethroids and organophosphates each above their respective MRL values. In ghee, residues of HCH & DDT both and of endosulfan exceeded the MRL values in 5 and 20% samples, respectively. Among organophosphates, only chlorpyriphos was detected with 9% samples showing its residue above MRL value. Irrespective of contamination levels, residues above the MRL values were more in ghee. More extensive study covering other agricultural regions/zones of Haryana has been suggested to know the overall scenario of contamination of milk products.

Assessing dormant season organophosphate use in California almonds

Organophosphate (OP) pesticides were recommended during the dormant season to control overwintering insects such as peach twig borer, San Jose scale, European red mite, and brown mite in California almond and stone fruit orchards. However, since 1990, dormant OP use had fallen under increased scrutiny due to surface water contamination concerns. Studies have shown positive correlation between OP use and residue load in surface water. The purpose of this study is to assess the trends and regional patterns of OP use in almond orchards, and to identify factors that may have influenced those trends, including weather, pest pressure, and use of alternatives to OP such as pyrethroid, dormant oils, and Bacillus thuringiensis (Bt) for the assessment of the impacts to surface water quality. Pesticide use data from the California Department of Pesticide Regulation were analyzed. Regression analyses were used to assess trends from 1992 to 2000, and a geographic information system (GIS) was used to visualize the spatial variation in pesticide use. Results from this study indicated that, statewide, dormant OP use decreased while the use of some alternatives, such as dormant pyrethroid, no dormant insecticides, and in-season pyrethroid, oil alone, and Bt, increased in the last 9 years. The significant decreasing trend of OP use was observed for the measures of kilogram per hectare crop planted, percentage of total planted hectare treated, and numbers of growers who applied dormant OP. The reduction of dormant OP use appeared in all major almond-growing counties. Correlation analyses revealed that more rain was associated with less dormant OP use. A higher percent of almond damage, or rejects, was related to higher OP use in the following dormant season and in-season periods. However, the effects of weather and percent of nut rejects can only explain small portion of the variations in dormant OP use. Therefore, in addition to weather and pest pressures, economic pressures and various outreach and extension programs may also have played a role in encouraging farmers to reduce their use of dormant OP.

Work Characteristics and Pesticide Exposures among Migrant Agricultural Families: A Community-Based Research Approach

There are few data on pesticide exposures of migrant Latino farmworker children, and access to this vulnerable population is often difficult. In this paper we describe a community-based approach to implement culturally appropriate research methods with a migrant Latino farmworker community in Oregon. Assessments were conducted in 96 farmworker homes and 24 grower homes in two agricultural communities in Oregon. Measurements included surveys of pesticide use and work protection practices and analyses of home-dust samples for pesticide residues of major organophosphates used in area crops. Results indicate that migrant farmworker housing is diverse, and the amounts and types of pesticide residues found in homes differ. Azinphos-methyl (AZM) was the pesticide residue found most often in both farmworker and grower homes. The median level of AZM in farmworker homes was 1.45 ppm compared to 1.64 ppm in the entry area of grower homes. The median level of AZM in the play areas of grower homes was 0.71 ppm. The levels of AZM in migrant farmworker homes were most associated with the distance from fields and the number of agricultural workers in the home. Although the levels of AZM in growers and farmworker homes were comparable in certain areas, potential for disproportionate exposures occur in areas of the homes where children are most likely to play. The relationship between home resident density, levels of pesticide residues, and play behaviors of children merit further attention.

Pesticide contamination of Jamaican environment. II. Insecticide residues in the rivers and shrimps of Rio Cobre basin, 1982-1996.

Only organochlorine (OC) residues were monitored by gas chromatographyin water, sediment and shrimp samples collected everymonth between July 1982 and August 1983 from therivers of Rio Cobre basin. In samples collected everyfour months during 1989–1990, and seven times duringJuly 1995–March 1996, OC and OP (organophosphates)residues were monitored. Carbamate and pyrethroidresidues were not monitored. The detection ofresidues in 1982–1983 was 54 to 100% in water andsediment, and 83 to 100% in shrimp samples fromvarious sampling stations in the four rivers. In otheryears, it ranged from about 40 to 100% in the threetypes of samples.In 1982–1983, DDE and dieldrin residues were found tobe much higher than those of lindane and α- andβ-endosulfan in Black River, Rio Pedro, ThomasRiver and Rio Cobre in the watershed. The ranges ofmeans of each residue in water (μg L-1), sediment(ng g-1) and shrimp (ng g-1) samples, respectively, were:DDE, 0.059–102.0, 3.44–13.97, 0.344–14.57;dieldrin, 0.026–173.6, 1.21–2.75, 0.427–5.59;α-endosulfan, bdl, 1.75–4.00, bdl;β-endosulfan, bdl (below detectable limits), 2.51–9.48, bdl;and lindane, (bdl), 0.110–0.319, 2.90.In 1989–1990 and 1995–1996, residues of six OCs and two OPs were detected quite regularly. DDE, dieldrinand Chlorpyrifos residues were much higher than thoseof the other insecticides. The range of their meansin water (μg L-1), sediment and shrimp (ng g-1),respectively, were: DDE, 1.66–19.76, 0.941–5.84,1.11–8.32; dieldrin, 0.077–7.22, 0.425–3.31,0.385–1.59; α-endosulfan, 0.034–1.25, 0.021–1.22, 0.032–3.62; β-endosulfan, 0.665–1.23,0.008–3.60, 0.005–3.97; endosulfan sulphate, 0.959–1.34, 0.035–3.08, 0.012–1.80; lindane, bdl,0.005–0.82, 1.19–1.56; chlorpyrifos, 0.702–4.06,0.005–1.51, 0.156–7.04; and diazinon, bdl, 0–0.150, 0.001–0.006. At the mouth of the river, whereit discharges into the sea, the levels of almost allthe residues were higher than upstream.

INCIDENCE OF PESTICIDE RESIDUES IN ADIPOSE TISSUE OF BEEF, PORK AND POULTRY FROM PLANTS LOCATED IN NORTHWESTERN MEXICO

ABSTRACT This study involved testing of adipose tissue from beef (208 samples), pork (112 samples) and poultry (39 samples) for pesticide residues, including nine different chlorinated hydrocarbons (CHC) and nine organophosphates (OP). Tissues were collected during a two‐year period (1996–1997) from plants located in the Northwestern Mexico, and determinations conducted by gas chromatography under international performance criteria. While none of the pork samples contained CHC residues, 17 (1996) and 11 (1997) beef samples contained either hexacholorobenzene, heptachlor, aldrin or dieldrin. Also, poultry samples (three in one year and four in the other) contained residues of either hexachlorobenzene, heptachlor or dieldrin. None of the tissues tested contained organophosphate residues above the detection limit. CHC incidences and concentrations were lower than those reported for other Mexican and Latin American regions, but higher than reports from the U.S. Based on the Mexican or U.S. tolerances, all concentrations of CHC found were nonviolative.

The Variation of Pesticide Residues in Fruits and Vegetables and the Associated Assessment of Risk

High levels of triazophos residues detected in carrots during routine monitoring led to the discovery of a wide variability between levels in individual roots. Conventional point estimates of consumer exposure were carried out. Due to the assumptions used, these calculations were likely to give rise to gross overestimates. In 1997, data were obtained for individual apples, pears, peaches, nectarines, oranges, bananas, and tomatoes that showed similar levels of variability in a range of organophosphate and carbamate residues. Point estimate models that had previously been used for intake estimates for carrots were not appropriate since it was necessary to take account of not only the variation of residue levels from crop item to crop item but also the variation in eating patterns in individual consumers. Probabilistic modeling was identified as a suitable way to produce multifactorial submodels and address some of the problems of combining distributions of consumption and residues. Consumption data from 1675 toddlers were linked with residue distributions from individual crop items not only to allow combinations of fruit consumed but also to allow for the variability in residue levels that occur between individual crop items. The model was also capable of taking account of the percentages of crops that did not contain any detectable residues; this information was available from initial screens of bulked samples and percentage of crop not treated in the case of carrots. The outputs from the models were given as percentages of consumers that could exceed a toxicological end point; this could be the acute reference dose or a factor of the no-observable-adverse-effect level. Modeling in this way was considered to give a realistic view of the likely short-term exposure and the output was used as an aid to decision making in terms of necessary regulatory action. As a result of high levels of triazophos detected in carrots during routine monitoring, studies were carried out to determine the variability of organophosphate residue levels in individual roots. Results obtained indicated that the highest residue levels could be 25 times the mean level in bulked samples (which were used in routine monitoring). Since sufficient levels of organophosphate compounds can give rise to toxicological effects after a single exposure, it was considered necessary to carry out assessments of short-term or acute consumer risk. At that time, models available worldwide were designed only to carry out point estimates of long-term exposure. From consumption data, it was possible to derive the levels of carrot consumption during a single day and calculations were carried out assuming all carrots contained the highest levels of residues found in trials. This led to a gross overestimate of likely exposure but was considered to give to intakes that eroded margins of safety; these were not a cause for extreme regulatory action. Further studies were carried out on other crops that may be eaten whole, at one sitting, and without processing to consider whether the large variability of organophosphate residues was a phenomenon that was common to other fruits and vegetables.

Modelling pesticide residues on greasy wool: using organophosphate and synthetic pyrethroid survey data

Summary. Several surveys have examined the relationship between organophosphate and synthetic pyrethroid residues in wool and associated treatments. These have been combined and summarised using a model of on-farm survey data. The model estimated the amount of chemical taken up by the wool at application. This was based on experimental breakdown rates of these pesticides on wool determined in controlled trials. For about 10% of survey results the chemical measured on the wool did not match the chemical the producer said was applied. A further 5% of results were excluded because the amount of chemical detected on the wool was inconsistent with the stated time of treatment and shearing. With the remaining results there was a very high variation in residues resulting from the same (stated) treatment. It is clear that many producers do not know what chemicals they have used or how much they applied. The wide variation in results suggests that some producers may apply excessive amounts of pesticides while others use too little to have a useful effect. The model estimated the amount of pesticide taken up by the fleece using the residue left at shearing and the known breakdown rate for a given method and chemical group. When organophosphates were applied by dipping, the amount of chemical taken up by the fleece appeared to increase as the length of the wool increased. This was generally higher than would be anticipated from label dose rates but was consistent with the stripping characteristics of these chemicals. Therefore dipping as soon as possible after shearing left much lower residues (&lt;10 mg/kg wool) than delayed treatment (often 10–30 mg/kg wool). In contrast the survey results suggest that the amount retained by sheep as a result of jetting decreased in longer wool. Jetting treatment rates appear to be lower than recommended, particularly for sheep with more than 6 months wool. Therefore jetting (as used by producers) left much lower residues in wool than dipping (with similar length wool) and was usually only above 10 mg/kg wool if carried out in the last 5 months before shearing, or if the same sheep received repeated treatments. The residue of synthetic pyrethroid retained in the fleece after dipping or long wool backliner application increased as the length of the wool increased at treatment, and appeared generally consistent with label recommendations. Current long wool backline products usually left residues of synthetic pyrethroid above 10 mg/kg on the wool. Short wool dipping left less than 10 mg/kg wool while off-shears backliners usually left average residue concentrations of about 2 mg/kg wool. Although the actual on-farm results vary 4-fold above and below the average, the model can be used to estimate the expected residue concentration and likely range of results from most standard on-farm organophosphate and synthetic pyrethroid treatments. This will allow improved provision of advice so that most producers can meet specified industry standards. It will allow wool buyers to estimate the risk of purchasing high residue wool based on producers’ statements about treatments applied.

Monitoring and Assessment of Swainson's Hawks in Argentina Following Restrictions on Monocrotophos Use, 1996–97

Approximately 6,000 dead Swainson's hawks (Buteo swainsoni) were discovered in the Pampas of Argentina in 1995–96. Subsequent meetings held between Argentine, US, Canadian, and Swiss personnel led to an agreement whereby chemical companies removed the organophosphate (OP) monocrotophos (MCP) from the area where mortalities had occurred in northern La Pampa province. We monitored hawks in the MCP exclusion zone from 28 November 1996 through 25 January 1997. We sampled 133 hawks for exposure to anti-cholinesterase insecticides, 131 of which showed no apparent signs of adverse effects. Two hawks had inhibited ChE that recovered over time. Feather and footwash samples from captured birds were tested for OP residues. One feather sample was positive for dimethoate; no footwash sample was positive for any of the OPs screened. Cholinesterase (ChE) activities from hawks in Argentina were (mean±SE, n=131) 0.674±0.014 total ChE, 0.236±0.006 acetylcholinesterase (AChE), and 0.438±0.013 butyrylcholinesterase (BChE). Mean plasma AChE from Argentine hawks was significantly depressed below North American reference values. Total ChE and BChE activities were not significantly different. Mortality due to OP poisoning was not found in the MCP exclusion zone in northern La Pampa, though it continued outside of the zone where MCP was used, both legally and illegally. Education campaigns and extension efforts, emphasizing the local MCP restrictions, were effective in controlling Swainson's hawk mortalities in the study area where substantial mortality occurred the previous two years.

Neurophysiological function in farm workers exposed to organophosphate pesticides.

To investigate neurophysiological effects of low-level exposure to foliar organophosphate residues during one season among agricultural workers, the authors performed a cross-sectional study of 67 Hispanic farm workers and 68 age-, gender-, ethnicity-, and education-matched reference subjects. The neurophysiological examination included sensory and motor nerve conduction and neuromuscular junction testing. Erythrocyte cholinesterase activity was measured at the time of examination. No statistically significant neurophysiological differences between the exposed and reference groups were observed. Farm workers and reference subjects had similar sensory nerve latency and amplitude (sural), motor nerve conduction velocity (ulnar), and neuromuscular junction function (ulnar). No relationship between duration of exposure during the season and electrophysiological measures of nerve function was found. Exposure of farm workers to the low levels of organophosphate pesticides during one season experienced by farm workers in this study was not associated with impaired peripheral neurophysiological function.

Fate of Summertime Airborne Organophosphate Pesticide Residues in the Sierra Nevada Mountains

AbstractThis study examines the processes of dilution, degradation, and sorption to plant foliage of organophosphate (OP) pesticides during the summertime in an air corridor originating in the southern Central Valley of California and moving into the nearby Sierra Nevada mountains. Residues of chlorpyrifos, methidathion, and their oxons were examined in air and pine needles at three sites in the southern Sierra to delineate the role these processes play in the atmospheric fate of these residues. At the site closest to the Central Valley, we found relatively high levels of parent OPs and oxons in needle and air samples. At higher elevations needles contained lesser amounts of OP residues and at lower frequency, while air primarily contained the oxon form. With increasing elevation the ratio of thion to oxon form of chlorpyrifos in air decreased from 1.85 to 0.46 indicating that atmospheric oxidation was occuring. Based on the amounts of foliar deposition found, we estimate that during summer months nearly 16 kg of chlorpyrifos and its oxon may enter Sequoia National Park plant foliage. We deduce that for airborne OP insecticides, foliar deposition is a significant summertime fate process, along with atmospheric degradation and dilution.