Agricultural task and exposure to organophosphate pesticides among farmworkers

Little is known about pesticide exposure among farmworkers, and even less is known about the exposure associated with performing specific farm tasks. Using a random sample of 213 farmworkers in 24 communities and labor camps in eastern Washington State, we examined the association between occupational task and organophosphate (OP) pesticide residues in dust and OP metabolite concentrations in urine samples of adult farmworkers and their children. The data are from a larger study that sought to test a culturally appropriate intervention to break the take-home pathway of pesticide exposure. Commonly reported farm tasks were harvesting or picking (79.2%), thinning (64.2%), loading plants or produce (42.2%), planting or transplanting (37.6%), and pruning (37.2%). Mixing, loading, or applying pesticide formulations was reported by 20% of our sample. Workers who thinned were more likely than those who did not to have detectable levels of azinphos-methyl in their house dust (92.1% vs. 72.7%; p = 0.001) and vehicle dust (92.6% vs. 76.5%; p = 0.002). Thinning was associated with higher urinary pesticide metabolite concentrations in children (91.9% detectable vs. 81.3%; p = 0.02) but not in adults. Contrary to expectation, workers who reported mixing, loading, or applying pesticide formulations had lower detectable levels of pesticide residues in their house or vehicle dust, compared with those who did not perform these job tasks, though the differences were not significant. Future research should evaluate workplace protective practices of fieldworkers and the adequacy of reentry intervals for pesticides used during thinning.     

Farmworker and nonfarmworker Latino immigrant men in North Carolina have high levels of specific pesticide urinary metabolites

This article compares detections and concentrations of specific organophosphate (OP), bis-dithiocarbamate, and pyrethroid pesticide urinary metabolites among Latino male farmworkers and nonfarmworkers in North Carolina. Data are from interviews and urine samples collected in 2012 and 2013. Farmworkers and nonfarmworkers frequently had detections for OP and pyrethroid pesticide urinary metabolites. Detection of bis-dithiocarbamate urinary metabolites was less frequent, but substantial among the nonfarmworkers. The concentrations of organophosphate, bis-dithiocarbamate, and pyrethroid pesticide urinary metabolites were high for farmworkers and nonfarmworkers compared to National Health and Nutrition Examination Survey results. Pesticide urinary metabolite detection was not associated with occupation in nonfarmworkers. Research for reducing pesticide exposure among farmworkers remains important; research is also needed to determine pesticide exposure pathways among Latino nonfarmworkers.     

Organophosphate pesticide exposure and neurobehavioral performance in agricultural and non-agricultural Hispanic workers

Our understanding of the health risks of farmworkers exposed to pesticides in their work and home environments is rapidly increasing, although studies designed to examine the possible neurobehavioral effects of low-level chronic pesticide exposure are limited. We measured dialkyl phosphate urinary metabolite levels, collected environmental dust samples from a subset of homes, obtained information on work practices, and conducted neurobehavioral tests on a sample of farmworkers in Oregon. Significant correlations between urinary methyl metabolite levels and total methyl organophosphate (azinphos-methyl, phosmet, malathion) house dust levels were observed. We found the neurobehavioral performance of Hispanic immigrant farmworkers to be lower than that observed in a nonagricultural Hispanic immigrant population, and within the sample of agricultural workers there was a positive correlation between urinary organophosphate metabolite levels and poorer performance on some neurobehavioral tests. These findings add to an increasing body of evidence of the association between low levels of pesticide exposure and deficits in neurobehavioral performance.     

Para niños saludables: a community intervention trial to reduce organophosphate pesticide exposure in children of farmworkers

BACKGROUND: Exposure to organophosphate (OP) pesticides is an occupational hazard for farmworkers and affects their children through the take-home pathway. OBJECTIVES: We examined the effectiveness of a randomized community intervention to reduce pesticide exposure among farmworkers and their children. METHODS: We conducted a baseline survey of a cross-sectional sample of farmworkers (year 1) in 24 participating communities. Communities were randomized to intervention or control. After 2 years of intervention, a new cross-sectional survey of farmworkers was conducted (year 4). Farmworkers with a child 2-6 years of age were asked to participate in a substudy in which urine was collected from the farmworker and child, and dust was collected from the home and the vehicle driven to work. RESULTS: The median concentration of urinary metabolites was higher in year 4 than in year 1 for dimethylthiophosphate (DMTP) and dimethyldithiophosphate in adults and for DMTP for children. There were significant increases within both the intervention and control communities between year 1 and year 4 (p < 0.005); however, the differences were not significant between study communities after adjusting for year (p = 0.21). The dust residue data showed azinphos-methyl having the highest percentage of detects in vehicles (86% and 84% in years 1 and 4, respectively) and in house dust (85% and 83% in years 1 and 4, respectively). There were no significant differences between intervention and control communities after adjusting for year (p = 0.49). CONCLUSIONS: We found no significant decreases in urinary pesticide metabolite concentrations or in pesticide residue concentrations in house and vehicle dust from intervention community households compared with control community households after adjusting for baseline. These negative findings may have implications for future community-wide interventions.     

Organophosphorus pesticide exposure of urban and suburban preschool children with organic and conventional diets

We assessed organophosphorus (OP) pesticide exposure from diet by biological monitoring among Seattle, Washington, preschool children. Parents kept food diaries for 3 days before urine collection, and they distinguished organic and conventional foods based on label information. Children were then classified as having consumed either organic or conventional diets based on analysis of the diary data. Residential pesticide use was also recorded for each home. We collected 24-hr urine samples from 18 children with organic diets and 21 children with conventional diets and analyzed them for five OP pesticide metabolites. We found significantly higher median concentrations of total dimethyl alkylphosphate metabolites than total diethyl alkylphosphate metabolites (0.06 and 0.02 micro mol/L, respectively; p = 0.0001). The median total dimethyl metabolite concentration was approximately six times higher for children with conventional diets than for children with organic diets (0.17 and 0.03 micro mol/L; p = 0.0003); mean concentrations differed by a factor of nine (0.34 and 0.04 micro mol/L). We calculated dose estimates from urinary dimethyl metabolites and from agricultural pesticide use data, assuming that all exposure came from a single pesticide. The dose estimates suggest that consumption of organic fruits, vegetables, and juice can reduce children's exposure levels from above to below the U.S. Environmental Protection Agency's current guidelines, thereby shifting exposures from a range of uncertain risk to a range of negligible risk. Consumption of organic produce appears to provide a relatively simple way for parents to reduce their children's exposure to OP pesticides.     

Health symptoms and exposure to organophosphate pesticides in farmworkers

BACKGROUND: Few studies have examined the relationship between reported health symptoms and exposure to organophosphate (OP) pesticides. METHODS: Fisher's exact test was used to assess the relationship between self-reported health symptoms and indicators of exposure to OP pesticides in 211 farmworkers in Eastern Washington. RESULTS: The health symptoms most commonly reported included headaches (50%), burning eyes (39%), pain in muscles, joints, or bones (35%), a rash or itchy skin (25%), and blurred vision (23%). Exposure to pesticides was prevalent. The proportion of detectable samples of various pesticide residues in house and vehicle dust was weakly associated with reporting certain health symptoms, particularly burning eyes and shortness of breath. No significant associations were found between reporting health symptoms and the proportion of detectable urinary pesticide metabolites. CONCLUSIONS: Certain self-reported health symptoms in farmworkers may be associated with indicators of exposure to pesticides. Longitudinal studies with more precise health symptom data are needed to explore this relationship further.     

Biological monitoring survey of organophosphorus pesticide exposure among pre-school children in the Seattle metropolitan area

In this study we assessed organophosphorus (OP) pesticide exposure among children living in two Seattle metropolitan area communities by measuring urinary metabolites, and identified possible exposure risk factors through a parental interview. We recruited children in clinic and outpatient waiting rooms. We obtained spot urine samples in the spring and fall of 1998 from 110 children ages 2-5 years, from 96 households. We analyzed urine samples for six dialkylphosphate (DAP) compounds, the common metabolites of the OP pesticides. Through parental interviews we gathered demographic and residential pesticide use data. At least one of the DAP metabolites was measured in 99% of the children, and the two predominant metabolites (DMTP and DETP) were measured in 70-75% of the children. We found no significant differences in DAP concentrations related to season, community, sex, age, family income, or housing type. Median concentrations of dimethyl and diethyl DAPs were 0.11 and 0.04 micromol/L, respectively (all children). Concentrations were significantly higher in children whose parents reported pesticide use in the garden (0.19 vs. 0.09 micromol/L for dimethyl metabolites, p = 0.05; 0.04 vs. 0.03 micromol/L for diethyl metabolites, p = 0.02), but were not different based on reported pet treatment or indoor residential use. Nearly all children in this study had measurable levels of OP pesticide metabolites. Some of this exposure was likely due to diet. Garden pesticide use was associated with elevated metabolite levels. It is unlikely that these exposure levels would cause acute intoxication, but the long-term health effects of such exposures are unknown. We recommend that OP pesticide use be avoided in areas where children are likely to play.     

Organophosphorus pesticide urinary metabolite levels of children in farmworker households in eastern North Carolina

BACKGROUND: Organophosphorus (OP) pesticide urinary metabolite levels in a sample of farmworker children in North Carolina are documented and compared to national reference data. The relative importance of para-occupational, residential, and environment risk factors are delineated. METHODS: Urine samples were collected from 60 farmworker children 1-6 years of age, and interviews were completed by their mothers. Urine samples were analyzed for the dialkylphosphate (DAP) metabolites of OP pesticides. Summed molar concentrations of the diethyl and dimethyl DAP metabolites provided summary measures. RESULTS: The farmworker children had relatively high levels of OP pesticide urinary metabolites compared to national reference data; for example, participating children had higher geometric means for diethylphosphate (DEP), diethylthiophosphate (DETP), and the summed diethyl metabolites. However, analyses found no pattern of significant associations between predictors and metabolite levels. CONCLUSIONS: Future research requires greater precision in sampling and measurement to determine the risk factors for pesticide exposure among farmworker children.     

Biologically based pesticide dose estimates for children in an agricultural community

Current pesticide health risk assessments in the United States require the characterization of aggregate exposure and cumulative risk in the setting of food tolerances. Biologic monitoring can aggregate exposures from all sources and routes, and can integrate exposures for chemicals with a common mechanism of action. Its value was demonstrated in a recent study of organophosphorus (OP) pesticide exposure among 109 children in an agricultural community in Washington State; 91 of the children had parents working in agriculture. We estimated individual OP pesticide doses from urinary metabolite concentrations with a deterministic steady state model, and compared them to toxicologic reference values. We evaluated doses by assuming that metabolites were attributable entirely to either azinphos-methyl or phosmet, the two OP pesticides used most frequently in the region. Creatinine-adjusted average dose estimates during the 6- to 8-week spraying season ranged from 0 to 36 microg/kg/day. For children whose parents worked in agriculture as either orchard applicators or as fieldworkers, 56% of the doses estimated for the spray season exceeded the U.S. Environmental Protection Agency (EPA) chronic dietary reference dose, and 19% exceeded the World Health Organization acceptable daily intake values for azinphos-methyl. The corresponding values for children whose parents did not work in agriculture were 44 and 22%, respectively. The percentage of children exceeding the relevant reference values for phosmet was substantially lower (< 10%). Single-day dose estimates ranged from 0 to 72 microg/kg/day, and 26% of these exceeded the EPA acute reference dose for azinphos-methyl. We also generated dose estimates by adjustment for total daily urine volume, and these estimates were consistently higher than the creatinine-adjusted estimates. None of the dose estimates exceeded the empirically derived no-observable-adverse-effect levels for these compounds. The study took place in an agricultural region during a period of active spraying, so the dose estimates for this population should not be considered representative of exposures in the general population. The findings indicate that children living in agricultural regions represent an important subpopulation for public health evaluation, and that their exposures fall within a range of regulatory concern. They also demonstrate that biologically based exposure measures can provide data for health risk evaluations in such populations.     

Do Workplace and Home Protective Practices Protect Farm Workers? Findings From the "For Healthy Kids" Study

OBJECTIVE:: To assess associations of protective workplace and home practices with pesticide exposure levels. METHODS:: Using data from orchard workers in the Yakima Valley, Washington, we examined associations of workplace and home protective practices with (1) urinary metabolite concentrations of dimethylthiophosphate (DMTP) in adults and children aged 2 to 6 years and (2) azinphos-methyl levels in house and vehicle dust. RESULTS:: Data were collected from 95 orchard workers and 94 children. Contrary to expectation, adult farm workers who wore boots or washed hands using hand sanitizer had higher concentrations of DMTP than those who did not. Children who attended daycare had higher DMTP concentrations than children who did not. CONCLUSIONS:: Few workplace or home practices were associated with pesticide exposure levels; workers who used hand sanitizer had higher concentrations of DMTP, as did children who attended daycare.     

Organophosphorous pesticide exposure increases the frequency of sperm sex null aneuploidy.

It has been estimated that 4 of 1,000 live births and 35% of spontaneous abortions are aneuploid and that an important proportion of embryo and newborn aneuploidy is of paternal origin. Exposure to organophosphorous pesticides (OP) has been associated with sperm hyperploidy/polyploidy. Therefore, we aimed to assess the frequency of sperm aneuploidy (X, Y, and 18) and its relationship with urinary OP metabolites in agricultural workers. We performed multicolor fluorescence in situ hybridization on samples from nine men obtained before and during the pesticide spraying season to assess sperm aneuploidy. We measured urinary OP metabolite levels by gas-liquid chromatography. Aneuploidies were found in 0.67% of total sperm nuclei. The most frequent aneuploidy was the lack of a sexual chromosome or sex null (0.19%), followed by XY18 (0.15%) and XY18-18 (0.06%). OP metabolites detected at higher concentrations were dimethylthiophosphate, dimethyldithiophosphate, and diethylphosphate (DEP). There were no differences in average aneuploidy frequency or urinary metabolite levels between samples collected before and after exposure. However, Poisson regression analysis adjusted for age, alcohol intake, and sperm concentration showed significant associations between OP metabolite concentrations and increased frequency of sperm aneuploidies. The association was more evident between DEP and sex null, and the risk increased further during the spraying season. Thus, OP exposure could interfere with sperm chromosome segregation and increase the risk for genetic syndromes, such as Turner's. Further studies are required to assess the prevalence of spontaneous abortions, birth defects, and genetic syndromes in agricultural communities.     

Evaluation of take-home organophosphorus pesticide exposure among agricultural workers and their children

We analyzed organophosphorus pesticide exposure in 218 farm worker households in agricultural communities in Washington State to investigate the take-home pathway of pesticide exposure and to establish baseline exposure levels for a community intervention project. House dust samples (n = 156) were collected from within the homes, and vehicle dust samples (n = 190) were collected from the vehicles used by the farm workers to commute to and from work. Urine samples were obtained from a farm worker (n = 213) and a young child (n = 211) in each household. Dust samples were analyzed for six pesticides, and urine samples were analyzed for five dialkylphosphate (DAP) metabolites. Azinphosmethyl was detected in higher concentrations (p < 0.0001) than the other pesticides: geometric mean concentrations of azinphosmethyl were 0.53 micro g/g in house dust and 0.75 micro g/g in vehicle dust. Dimethyl DAP metabolite concentrations were higher than diethyl DAP metabolite concentrations in both child and adult urine (p < 0.0001). Geometric mean dimethyl DAP concentrations were 0.13 micro mol/L in adult urine and 0.09 micro mol/L in child urine. Creatinine-adjusted geometric mean dimethyl DAP concentrations were 0.09 micro mol/g in adult urine and 0.14 micro mol/g in child urine. Azinphosmethyl concentrations in house dust and vehicle dust from the same household were significantly associated (r2 = 0.41, p < 0.0001). Dimethyl DAP levels in child and adult urine from the same household were also significantly associated (r2 = 0.18, p < 0.0001), and this association remained when the values were creatinine adjusted. The results of this work support the hypothesis that the take-home exposure pathway contributes to residential pesticide contamination in agricultural homes where young children are present.     

Dietary intake and its contribution to longitudinal organophosphorus pesticide exposure in urban/suburban children

BACKGROUND: The widespread use of organophosphorus (OP) pesticides has led to frequent exposure in adults and children. Because such exposure may cause adverse health effects, particularly in children, the sources and patterns of exposure need to be studied further. OBJECTIVES: We assessed young urban/suburban children's longitudinal exposure to OP pesticides in the Children's Pesticide Exposure Study (CPES) conducted in the greater Seattle, Washington, area, and used a novel study design that allowed us to determine the contribution of dietary intake to the overall OP pesticide exposure. METHODS: Twenty-three children 3-11 years of age who consumed only conventional diets were recruited for this 1-year study conducted in 2003-2004. Children switched to organic diets for 5 consecutive days in the summer and fall sampling seasons. We measured specific urinary metabolites for malathion, chlorpyrifos, and other OP pesticides in urine samples collected twice daily for a period of 7, 12, or 15 consecutive days during each of the four seasons. RESULTS: By substituting organic fresh fruits and vegetables for corresponding conventional food items, the median urinary metabolite concentrations were reduced to nondetected or close to non-detected levels for malathion and chlorpyrifos at the end of the 5-day organic diet intervention period in both summer and fall seasons. We also observed a seasonal effect on the OP urinary metabolite concentrations, and this seasonality corresponds to the consumption of fresh produce throughout the year. CONCLUSIONS: The findings from this study demonstrate that dietary intake of OP pesticides represents the major source of exposure in young children.     

Biologic monitoring to characterize organophosphorus pesticide exposure among children and workers: an analysis of recent studies in Washington State

We examined findings from five organophosphorus pesticide biomonitoring studies conducted in Washington State between 1994 and 1999. We compared urinary dimethylthiophosphate (DMTP) concentrations for all study groups and composite dimethyl alkylphosphate (DMAP) concentrations for selected groups. Children of pesticide applicators had substantially higher metabolite levels than did Seattle children and farmworker children (median DMTP, 25 microg/L; p < 0.0001). Metabolite levels of children living in agricultural communities were elevated during periods of crop spraying. Median DMTP concentrations for Seattle children and farmworker children did not differ significantly (6.1 and 5.8 microg/L DMTP, respectively; p = 0.73); however, the DMAP concentrations were higher for Seattle children than for farmworker children (117 and 87 nmol/L DMAP, respectively; p = 0.007). DMTP concentrations of U.S. children 6-11 years of age (1999-2000 National Health and Nutrition Examination Survey population) were higher than those of Seattle children and farmworker children at the 75th, 90th, and 95th percentiles. DMTP concentrations for workers actively engaged in apple thinning were 50 times higher than DMTP concentrations for farmworkers sampled outside of peak exposure periods. We conclude that workers who have direct contact with pesticides should continue to be the focus of public health interventions and that elevated child exposures in agricultural communities may occur during active crop-spraying periods and from living with a pesticide applicator. Timing of sample collection is critical for the proper interpretation of pesticide biomarkers excreted relatively soon after exposure. We surmise that differences in dietary exposure can explain the similar exposures observed among farmworker children, children living in the Seattle metropolitan area, and children sampled nationally.     

Farmworker exposure to organophosphorus pesticide residues during apple thinning in central Washington State

The purpose of this study was to characterize worker exposure to azinphos-methyl (Guthion) over an entire 4-6 week apple-thinning season. Twenty workers from three work sites in the Chelan-Douglas County region of Washington state were recruited for the study. Exposure potential was estimated by dislodgeable foliar residue measurements, and individual exposures were estimated by biological monitoring through urinary metabolites. Measureable azinphos-methyl residues were found on apple foliage at all sites throughout the six-week sampling period, indicating continuous exposure potential (median residue level of 0.5 microgram/cm2). Measurable levels of the urinary dialkylphosphate metabolite, DMTP, were found in virtually all urine samples (limit of detection = 0.04 microgram/mL). Mean DMTP concentrations differed significantly across sites (0.53, 0.29, and 0.90 microgram/mL for Sites 1-3, respectively; analysis of variance, p < .002), and intraindividual variability was much greater than interindividual differences. Group mean DMTP concentrations at each site fluctuated according to foliar residue levels. Measurable DMTP concentrations were found in 9% of reference workers, ranging from 0.04-0.18 microgram/mL. Cholinesterase activity levels monitored with a field test kit were not considered reliable due to temperature changes of the instrument.     

Cumulative organophosphate pesticide exposure and risk assessment among pregnant women living in an agricultural community: a case study from the CHAMACOS cohort

Approximately 230,000 kg of organophosphate (OP) pesticides are applied annually in California's Salinas Valley. These activities have raised concerns about exposures to area residents. We collected three spot urine samples from pregnant women (between 1999 and 2001) enrolled in CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas), a longitudinal birth cohort study, and analyzed them for six dialkyl phosphate metabolites. We used urine from 446 pregnant women to estimate OP pesticide doses with two deterministic steady-state modeling methods: method 1, which assumed the metabolites were attributable entirely to a single diethyl or dimethyl OP pesticide; and method 2, which adapted U.S. Environmental Protection Agency (U.S. EPA) draft guidelines for cumulative risk assessment to estimate dose from a mixture of OP pesticides that share a common mechanism of toxicity. We used pesticide use reporting data for the Salinas Valley to approximate the mixture to which the women were exposed. Based on average OP pesticide dose estimates that assumed exposure to a single OP pesticide (method 1), between 0% and 36.1% of study participants' doses failed to attain a margin of exposure (MOE) of 100 relative to the U.S. EPA oral benchmark dose(10) (BMD(10)), depending on the assumption made about the parent compound. These BMD(10) values are doses expected to produce a 10% reduction in brain cholinesterase activity compared with background response in rats. Given the participants' average cumulative OP pesticide dose estimates (method 2) and regardless of the index chemical selected, we found that 14.8% of the doses failed to attain an MOE of 100 relative to the BMD(10) of the selected index. An uncertainty analysis of the pesticide mixture parameter, which is extrapolated from pesticide application data for the study area and not directly quantified for each individual, suggests that this point estimate could range from 1 to 34%. In future analyses, we will use pesticide-specific urinary metabolites, when available, to evaluate cumulative OP pesticide exposures.     

Determining the probability of pesticide exposures among migrant farmworkers: results from a feasibility study.

BACKGROUND: Migrant and seasonal farmworkers are exposed to pesticides through their work with crops and livestock. Because workers are usually unaware of the pesticides applied, specific pesticide exposures cannot be determined by interviews. We conducted a study to determine the feasibility of identifying probable pesticide exposures based on work histories. METHODS: The study included 162 farm workers in seven states. Interviewers obtained a lifetime work history including the crops, tasks, months, and locations worked. We investigated the availability of survey data on pesticide use for crops and livestock in the seven pilot states. Probabilities of use for pesticide types (herbicides, insecticides, fungicides, etc.) and specific chemicals were calculated from the available data for two farm workers. The work histories were chosen to illustrate how the quality of the pesticide use information varied across crops, states, and years. RESULTS: For most vegetable and fruit crops there were regional pesticide use data in the late 1970s, no data in the 1980s, and state-specific data every other year in the 1990s. Annual use surveys for cotton and potatoes began in the late 1980s. For a few crops, including asparagus, broccoli, lettuce, strawberries, plums, and Christmas trees, there were no federal data or data from the seven states before the 1990s. CONCLUSIONS: We conclude that identifying probable pesticide exposures is feasible in some locations. However, the lack of pesticide use data before the 1990s for many crops will limit the quality of historic exposure assessment for most workers.     

Urinary organophosphate metabolite levels in Palestinian pregnant women: results of the Middle East Regional Cooperation Project

The purpose of the study was to measure urinary organophosphate (OP) metabolites in Palestinian pregnant women, and to compare levels with those in pregnant women in Jerusalem and women from the general population in Israel. We measured six dialkyl phosphates in urine samples collected from 148 pregnant women from the West Bank area. Median total dimethyl phosphate (DM_total) levels were significantly lower in Palestinian women compared to Jerusalem pregnant women and women in Israel (p = 0.041). In Palestinian women reporting that their place of residence was near an agricultural field, DM_total levels were significantly higher (p = 0.037). Lower urinary excretion of dimethyl phosphate pesticide metabolites in Palestinian women compared to Israeli women may result from lower consumption of fruits and vegetables in the Palestinian population. Our findings highlight differences in OP pesticide exposure in populations with close geographical proximity but with differences in culture, diet, lifestyle, and regulatory oversight of pesticides.     

Dialkylphosphorus metabolites in the urine and activities of esterases in the serum as biochemical indices for human absorption of organophosphorus pesticides

Ninety-seven agricultural workers were monitored for absorption of the organophosphorus pesticides methidathion, vamidothion, and azinphos-methyl, which were sprayed in an orchard during two seasons. Low levels of only one dialkylphosphorus metabolite (dimethyl phosphorothioate) were found in only eight workers in pre-exposure urine samples. More than one dialkylphosphorus metabolite was detected in almost all exposed individuals in after-exposure urine samples. The highest concentrations were measured after exposure to azinphos-methyl; the median concentrations of dimethyl phosphorodithioate and dimethyl phosphorothioate were 0.92 and 0.78 nmol/mg creatinine with a concentration range up to 14.3 and 53.7, respectively. Three diethylphosphorus metabolites were also detected in some samples, but at lower concentrations. Cholinesterase activities were decreased (31–48%) in the serum of 12 workers; four of those workers had no dialkylphosphorus metabolites in the urine. Paraoxonase and arylesterase activities in the serum were unaffected by the absorption of pesticides, and there was no correlation between the activities of these esterases and the metabolite concentrations in the urine. This study confirmed that dialkylphosphorus metabolites in the urine are a more sensitive index of absorption than cholinesterase inhibition in the serum but lack of correlation between cholinesterase inhibition and metabolite concentration indicates that both parameters should be monitored.     

Assessment of organophosphorous pesticide exposures in the diets of preschool children in Washington State

Twenty-four hour duplicate diet sampling was employed to investigate dietary pesticide exposures of children aged 2 to 5 years. Duplicate diets were collected from seven children living in the Seattle metropolitan area and six children living in Chelan and Douglas counties in Central Washington. Diet samples were collected from each child in the summer and again in the fall, and total daily diets were divided into four food categories: fresh fruits and vegetables, beverages, processed foods, and dairy products. A total of 88 individual food category samples were collected and analyzed for 15 organophosphorous (OP) pesticides. Three of the 13 children had no detectable OP pesticides in either of their diet samples, and 14 of the 26 duplicate diets did not contain detectable levels of OP pesticides. Sixteen individual food category samples contained detectable levels of at least one OP pesticide and two of these samples contained detectable levels of two OP pesticides. Of the 15 targeted pesticides, 6 were detected: azinphosmethyl, chlorpyrifos, malathion, methidathion, methyl parathion, and phosmet. Azinphosmethyl was detected most frequently (10% of all samples), particularly in samples containing apples or apple juice. The fresh fruits and vegetable category had the most frequent pesticide determinations, followed by beverages. OP pesticides were not present at detectable levels in any of the dairy samples. Malathion was the only OP pesticide detected in processed food samples, appearing in 4 of the 26 samples (15%). No detections were above the legal tolerances for residues on produce, however the acute population-adjusted reference dose (aPAD) for chlorpyrifos exposure of 1.7 microg/kg/day was exceeded by one subject during one sampling event. This subject's cumulative daily dose of chlorpyrifos equivalents was estimated to be 2.5 microg/kg/day.