Pesticide exposures, cholinesterase depression, and symptoms among North Carolina migrant farmworkers

Association of ambient air pollution and pesticide mixtures on respiratory inflammatory markers in agricultural communities

Air pollution exposure is associated with adverse respiratory health outcomes. Evidence from occupational and community-based studies also suggests agricultural pesticides have negative health impacts on respiratory health. Although populations are exposed to multiple inhalation hazards simultaneously, multidomain mixtures (e.g. environmental and chemical pollutants of different classes) are rarely studied. We investigated the association of ambient air pollution-pesticide exposure mixtures with urinary leukotriene E4 (LTE4), a respiratory inflammation biomarker, for 75 participants in four Central California communities over two seasons. Exposures included three criteria air pollutants estimated via the Community Multiscale Air Quality model (fine particulate matter, ozone, and nitrogen dioxide) and urinary metabolites of organophosphate (OP) pesticides (total dialkyl phosphates (DAPs), total diethyl phosphates (DE), and total dimethyl phosphates (DM)). We implemented multiple linear regression models to examine associations in single pollutant models adjusted for age, sex, asthma status, occupational status, household member occupational status, temperature, and relative humidity, and evaluated whether associations changed seasonally. We then implemented Bayesian kernel machine regression (BKMR) to analyse these criteria air pollutants, DE, and DM as a mixture. Our multiple linear regression models indicated an interquartile range (IQR) increase in total DAPs was associated with an increase in urinary LTE4 in winter (β: 0.04, 95% CI: [0.01, 0.07]). Similarly, an IQR increase in total DM was associated with an increase in urinary LTE4 in winter (β:0.03, 95% CI: [0.004, 0.06]). Confidence intervals for all criteria air pollutant effect estimates included the null value. BKMR analysis revealed potential non-linear interactions between exposures in our air pollution-pesticide mixture, but all confidence intervals contained the null value. Our analysis demonstrated a positive association between OP pesticide metabolites and urinary LTE4 in a low asthma prevalence population and adds to the limited research on the joint effects of ambient air pollution and pesticides mixtures on respiratory health.

Mixed-Methods Assessment of Farmworkers' Perceptions of Workplace Compliance with Worker Protection Standards and Implications for Risk Perceptions and Protective Behaviors

INTRODUCTION

The Environmental Protection Agency (EPA)'s Worker Protection Standards is the primary set of legislation aimed at protecting farmworkers from occupational pesticide exposure in the United States. Previous studies suggest that worker adoption of Pesticide Protective Behaviors (PPBs) promoted by WPS is associated with lower urinary pesticide concentrations. However, adoption of PPBs is often outside of the control of individual farmworkers and dependent on workplace factors such as employer provisioning of Personal Protective Equipment (PPE) and access to trainings/resources.

METHODS

We conducted a mixed-method study including urinary pesticide biomonitoring, surveys, and interviews with 62 Latinx farmworkers in southwestern Idaho from April to July 2022. We integrated findings across the various data sources to identify emergent themes relating to farmworkers' perceptions of workplace compliance with WPS and potential implications for their pesticide risk perceptions, protective behaviors, and urinary pesticide concentrations.

RESULTS

Participants reported some indications of poor workplace compliance with WPS regulations, notably inconsistent access to clean handwashing stations and notification of pesticide applications. Some farmworkers, particularly pesticide applicators, viewed herbicides to be categorically safer than other classes of pesticides such as insecticides; these perceptions appeared to influence protective behaviors, such as the relatively low use of PPE while applying herbicides. These findings are underscored by the higher concentrations of biomarkers of herbicides, but not insecticides, among pesticide applicators compared with non-applicators (e.g. median 2,4-D concentrations = 1.40 µg/L among applicators and 0.69 µg/L among non-applicators). Participants further reported concerns regarding the inadequacy of pesticide safety training, pesticide drift, and the lack of communication regarding pesticide applications on and near fields where they are working.

DISCUSSION

Participants' perceptions that herbicides are categorically safer than other pesticide classes is in direct conflict with WPS training, raising concerns about discrepancies between WPS instruction and other on-the-job training, as well as the inadequate provisioning of PPE during the application of certain pesticides. Our findings also suggest that current WPS regulations may not sufficiently address farmworkers' concerns, particularly in regard to pesticide drift.

Examination of urinary pesticide concentrations, protective behaviors, and risk perceptions among Latino and Latina farmworkers in Southwestern Idaho

INTRODUCTION

Studies have documented high levels of pesticide exposure among men farmworkers; however, few have examined exposures or the experiences of women farmworkers. Data gaps also exist regarding farmworkers' perceived risk and control related to pesticides, information that is critical to develop protective interventions.

OBJECTIVE

We aimed to compare urinary pesticide biomarker concentrations between Latino and Latina farmworkers and examine associations with occupational characteristics, risk perceptions, perceived control, and protective behaviors.

METHODS

We enrolled a convenience sample of 62 farmworkers (30 men and 32 women) during the pesticide spray season from April-July 2022 in southwestern Idaho. Participants were asked to complete two visits within a seven-day period; at each visit, we collected a urine sample and administered a questionnaire assessing demographic and occupational information. Urine samples were composited and analyzed for 17 biomarkers of herbicides and of organophosphate (OP) and pyrethroid insecticides.

RESULTS

Ten pesticide biomarkers (TCPy, MDA, PNP, 3-PBA, 4-F-3-PBA, cis- and trans-DCCA, 2,4-D, Glyphosate, AMPA) were detected in >80% of samples. Men and women had similar urinary biomarker concentrations (p = 0.19-0.94); however, women worked significantly fewer hours than men (p = 0.01), wore similar or greater levels of Personal Protective Equipment (PPE), and were slightly more likely to report having experienced an Acute Pesticide Poisoning (26% of women vs. 14% of men; p = 0.25). We observed inconsistencies in risk perceptions, perceived control, and protective behaviors among men.

DISCUSSION

Our study is one the first to examine pesticide exposure and risk perceptions among a cohort of farmworkers balanced on gender. Taken with previous findings, our results suggest that factors such as job tasks, biological susceptibility, or access to trainings and protective equipment might uniquely impact women farmworkers' exposure and/or vulnerability to pesticides. Women represent an increasing proportion of the agricultural workforce, and larger studies are needed to disentangle these findings.

Feasibility of Portable Fingerstick Cholinesterase Testing in Adolescents in South Texas

Adolescents are particularly vulnerable to the impacts of pesticide exposures, which can be assessed using surveys, environmental measurements, and biomonitoring. Biomonitoring of blood cholinesterase can be used to determine if an individual has been exposed to pesticides. A limitation of blood cholinesterase testing can be the use of a laboratory as well as time to receive results. In addition to laboratory tests, there are fingerstick cholinesterase (ChE) tests, which can eliminate the need for laboratory testing. Some populations, such as farmworkers, would benefit through fingerstick ChE tests. The objective of this pilot study is to determine the feasibility (eg, can the testing be used to assess ChE levels) of using fingerstick ChE testing in adolescent populations living along the Texas-Mexico border where adolescents who often engage in farm work live. A sub-objective was to explore differences in ChE levels by sex. The Model 400 Test-Mate ChE kit by EQM Research Inc (Cincinnati, OH) was used to assess for ChE inhibition in the participants, specifically acetylcholinesterase (AChE), which is 1 of the 2 ChE enzymes. During the postassessment, males had a mean AChE value of 3.75 U/mL (95% CI 3.51-3.98); whereas females had a mean AChE value of 2.86 U/mL (95% CI 2.64-3.08), which was statistically significant. Overall, the study supports the use of field ChE testing in adolescent populations with a small percentage (6.90%) refusing to complete ChE testing.

Disseminating Pesticide Exposure Results to Farmworker and Nonfarmworker Families in an Agricultural Community: A Community-Based Participatory Research Approach

OBJECTIVE

The aim of this study was to examine the impact of a dissemination process to provide individual pesticide results to study participants.

METHODS

After working with community members to disseminate data, 37 participants were recontacted via an interview survey to assess the effectiveness of the dissemination process.

RESULTS

Almost all participants (97.3%) recalled a home visit from a health promoter; 29 (78.4%) correctly recalled that the health promoter used a thermometer or graphic to explain the results; 26 (70.3%) correctly interpreted graphics showing high and low exposure levels in adults and 75.7% correctly interpreted results for children.

CONCLUSIONS

The study results support the use of a community-based participatory research approach to decide how to best depict and disseminate study results, especially among participants who are often left out of the dissemination process.

Coping Strategies That Mitigate Against Symptoms of Depression Among Latino Farmworkers

Latino farmworkers have a higher rate of depression when compared with other Latinos and the general adult population in the United States. Researchers have suggested oppressive labor policies, acculturation stressor, anti-immigrant polices and attitudes, and the dangers associated to farm work as culprits to high rates of depression among farmworkers. We examined the traits farmworkers reported that helped them mitigate symptoms of depression. Our sample consisted of 64 adult male and female farmworkers who lived in western Texas and worked in Eastern New Mexico. We used the Center for Epidemiologic Studies Depression Scale Revised (CESD-R) and self-reports of symptoms of depression to assess for depression. We found that, among this sample, the rates of depression were similar to other studies and that farmworkers used cognitive restructuring strategies to mitigate symptoms of depression.

Molecular detection of M. tuberculosis and M. bovis and hematological and biochemical analyses in agricultural sprayers exposed to pesticides: A cross-sectional study in Punjab, Pakistan during 2014-2016

We determined the correlation between a pesticide exposure, physical health and susceptibility toward tuberculosis along with hematological indices and liver enzymes' alterations in sprayers exposed to pesticides. Molecular detection of Mycobacterium tuberculosis and Mycobacterium bovis was detected by targeting histone-like protein (hupB) gene. The WBC (white blood cells) and RBC (red blood cells) levels of male sprayers and non-sprayers were significantly different (P<0.05). In female spray workers, the WBC and neutrophils levels were significantly different as compared with non-sprayers. Overall, in both male and female pesticide-exposed sprayers, mean values of alanine amino transferase and aspartate amino transferase were higher as compared with unexposed workers. M. Tuberculosis were detected in 15% male sprayers and 36% female sprayers while, M. bovis was detected in 5% male sprayers and 10% female sprayers. A χ²-test indicated that there existed a significant different (P<0.05) between positive and negative M. tuberculosis and M. bovis in both male/female spray workers out of total. The susceptibility of pesticide-exposed sprayers to tuberculosis and alterations in hematology and liver enzymes is crucial for health. Toxic effects of pesticides may lead to a weak immune system and increased tuberculosis susceptibility.

Benefits, Facilitators, Barriers, and Strategies to Improve Pesticide Protective Behaviors: Insights from Farmworkers in North Carolina Tobacco Fields

Pesticide exposure is associated with deleterious health effects. Prior studies suggest Latino farmworkers perceive little control over their occupational health. Using the Health Belief Model as a theoretical guide, we explored the perceptions of Latino farmworkers working in tobacco in North Carolina (n = 72) about benefits and facilitators of pesticide protective behaviors as well as barriers, and strategies to overcome barriers to their use. Interviews were conducted with participants at farmworker housing during non-work time. Qualitative data were analyzed using ATLAS.ti. Farmworkers recognized pesticide protective behaviors as helping them to not get sick and stay healthy. Farmworkers perceived work experience as facilitating protective behaviors. Wetness in the field was the most commonly cited barrier to protective behavior use. To overcome this barrier, farmworkers suggested use of water-resistant outerwear, as well as packing a change of clothes for mid-day, with space and time to change provided by employers. Examination of the efficacy and feasibility of farmworkers' suggestions for addressing barriers is warranted. Training and behavior modeling by experienced peers may improve behavior adoption and perceived control.

High-Confidence Qualitative Identification of Organophosphorus Nerve Agent Adducts to Human Butyrylcholinesterase

In this study, a data-dependent, high-resolution tandem mass spectrometry (ddHRMS/MS) method capable of detecting all organophosphorus nerve agent (OPNA) adducts to human butyrylcholinesterase (BChE) was developed. After an exposure event, immunoprecipitation from blood with a BChE-specific antibody and digestion with pepsin produces a nine amino acid peptide containing the OPNA adduct. Signature product ions of this peptic BChE nonapeptide (FGES*AGAAS) offer a route to broadly screen for OPNA exposure. Taking this approach on an HRMS instrument identifies biomarkers, including unknowns, with high mass accuracy. Using a set of pooled human sera exposed to OPNAs as quality control (QC) materials, the developed method successfully identified precursor ions with <1 ppm and tied them to signature product ions with <5 ppm deviation from their chemical formulas. This high mass accuracy data from precursor and product ions, collected over 23 independent immunoprecipitation preparations, established method operating limits. QC data and experiments with 14 synthetic reference peptides indicated that reliable qualitative identification of biomarkers was possible for analytes >15 ng/mL. The developed method was applied to a convenience set of 96 unexposed serum samples and a blinded set of 80 samples treated with OPNAs. OPNA biomarkers were not observed in convenience set samples and no false positive or negative identifications were observed in blinded samples. All biomarkers in the blinded serum set >15 ng/mL were correctly identified. For the first time, this study reports a ddHRMS/MS method capable of complementing existing quantitative methodologies and suitable for identifying exposure to unknown organophosphorus agents.

Pesticides: Perceived Threat and Protective Behaviors Among Latino Farmworkers

OBJECTIVES

The purpose of this study was to assess the knowledge and beliefs of 72 Latino farmworkers in North Carolina about the threat of health effects of pesticides, including cancer. It sought to explore relationships between threat perceptions and pesticide protective behaviors observed in the field.

METHODS/RESULTS

Utilizing stepwise multiple regression, the authors found that years worked in agriculture in the United States was associated with decreased use of protective clothing.

CONCLUSION

Pesticide protective behaviors in the field may be improved by utilizing moderately experienced farmworkers (<10 years) as lay advisors to reinforce training.

Evaluation of oxidative stress and genotoxicity in organophosphorus insecticide formulators

The aim of this study was to evaluate genotoxicity and oxidative stress in workers who formulate organophosphorus (OP) pesticides. In this survey, blood leukocytes and erythrocytes of a group of 21 pesticide formulating workers and an equal number of control subjects were examined for genotoxicity and oxidative stress parameters. The mean comet tail length and mean comet length were used to measure DNA damage. Lipid peroxidation level, catalase, superoxide dismutase (SOD) and glutathione peroxidase activities in erythrocytes were analysed as biomarkers of oxidative stress. In addition, the acetylcholinesterase activity was measured as a biomarker of toxicity. The average duration of employment of workers in the factory was 97 months. Results indicated that chronic exposure (multiple5dose, greater than or equal to 6 months duration) to OP pesticides was associated with increased activities of catalase, SOD and glutathione peroxidase in erythrocytes. The level of lipid peroxidation and acetylcholinesterase activity did not show any significant differences between the two groups. The results also indicated that chronic exposure to OP pesticides was associated with increased DNA damage. It is concluded that human chronic exposure to OP pesticides may result in stimulated antioxidant enzymes and increased DNA damage in the absence of depressed acetylcholinesterase levels. Routine genotoxicity monitoring concomitant to acetylcholinesterase activity in workers occupationally exposed to OP insecticides is suggested.

Reflections on the process of using systematic review techniques to evaluate the literature regarding the neurotoxicity of low level exposure to organophosphate pesticides

We undertook a systematic review (incorporating meta-analysis) of the literature concerning the neurotoxicity of cumulative low level occupational exposure to organophosphate pesticides, which was published online by the journal Critical Reviews in Toxicology in 2012. As far as we are aware, we were the first research team to attempt quantitative evaluation of study findings on this topic, using meta-analysis. We wish to encourage others to apply systematic review techniques in chemical risk assessment to reduce bias, increase transparency and better inform public policy. We thought it would be useful to share our experience of undertaking a systematic review in the hope of dispelling misconceptions about the complexity, time and resource issues involved along with the view that meta-analysis is meaningless when studies are not homogeneous. In this commentary paper we reflect on aspects of the process which were relatively straightforward; aspects which were more challenging; the advantages of using systematic review techniques; and the advantages and limitations of using statistical techniques such as meta-analysis in this context.

Observed and self-reported pesticide protective behaviors of Latino migrant and seasonal farmworkers

Agricultural pesticide exposure has potential adverse health effects for farmworkers that may be reduced by pesticide protective behaviors (PPBs). The Environmental Protection Agency's (EPA) Worker Protection Standard (WPS) requires PPBs be taught to farmworkers prior to field work. Studies to date have not utilized observational methods to evaluate the degree to which PPBs are practiced by Latino migrant and seasonal farmworkers in the United States. The purpose of this study was to describe, compare, and contrast observed and self-reported PPBs used by Latino farmworkers; both PPBs that the WPS requires be taught and other PPBs were included. Observed and self-reported data were collected from 71 Latino farmworkers during the 2014 tobacco growing season in North Carolina. Participants were consistent in reporting and using long pants and closed shoes in the field most of the time. In addition, gloves, hats/bandanas, and water-resistant outerwear were frequently observed, although they are not required to be taught by the WPS. Farmworkers reported more long-sleeve (p=.028) and glove use (p=.000) than what was observed. It was uncommon to observe washing behavior before eating or drinking, even when washing supplies were available. Washing behaviors were significantly overreported for hand (p=.000; p=.000) and face (p=.000; p=.058) washing before eating and drinking in the field. This study documents that protective clothing behaviors that the WPS requires be taught, plus a few others are commonly practiced by Latino migrant and seasonal farmworkers, but washing behaviors in the field are not. Targeted strategies to improve washing behaviors in the field are needed.

The effectiveness of an educational intervention to improve knowledge and perceptions for reducing organophosphate pesticide exposure among Indonesian and South Australian migrant farmworkers

BACKGROUND

Farmworkers are at risk of exposure to organophosphate pesticides (OPs). Improvements of knowledge and perceptions about organophosphate (OP) exposure may be of benefit for the reduction in OP exposure.

PURPOSE

The purpose of this study was to examine the effectiveness of an educational intervention to improve knowledge and perceptions for reducing OP exposure among Indonesian and South Australian (SA) migrant farmworkers.

METHODS

This was a quasi-experimental study. The educational intervention used a method of group communication for 30 Indonesian farmworkers and individual communication for seven SA migrant farmworkers. Knowledge and perceptions about OP exposure were measured pre-intervention and 3 months after the intervention.

RESULTS

Unadjusted intervention effects at follow-up showed statistically significantly improved scores of knowledge (both adverse effects of OPs and self-protection from OP exposure), perceived susceptibility, and perceived barriers among Indonesian farmworkers compared with SA migrant farmworkers. Furthermore, these four significant variables in the unadjusted model and the two other variables (perceived severity and perceived benefits) were statistically significant after being adjusted for the level of education and years working as a farmworker. In contrast, knowledge about adverse effects of OPs was the only variable that was statistically significantly improved among SA migrant farmworkers. The results of this study suggests educational interventions using a method of group communication could be more effective than using individual intervention.

CONCLUSION

These improvements provide starting points to change health behavior of farmworkers, particularly to reduce OP exposure, both at the workplace and at home.

Meta-analysis on occupational exposure to pesticides--neurobehavioral impact and dose-response relationships

While the health impact of high exposures to pesticides is acknowledged, the impact of chronic exposures in the absence of acute poisonings is controversial. A systematic analysis of dose-response relationships is still missing. Its absence may provoke alternative explanations for altered performances. Consequently, opportunities for health prevention in the occupational and environmental field may be missed. Objectives were (1) quantification of the neurotoxic impact of pesticides by an analysis of functional alterations in workers measured by neuropsychological performance tests, (2) estimates of dose-response relationships on the basis of exposure duration, and (3) exploration of susceptible subgroups. The meta-analysis employed a random effects model to obtain overall effects for individual performance tests. Twenty-two studies with a total of 1758 exposed and 1260 reference individuals met the inclusion criteria. At least three independent outcomes were available for twenty-six performance variables. Significant performance effects were shown in adults and referred to both cognitive and motor performances. Effect sizes ranging from dRE=-0.14 to dRE=-0.67 showed consistent outcomes for memory and attention. Relationships between effect sizes and exposure duration were indicated for individual performance variables and the total of measured performances. Studies on adolescents had to be analyzed separately due to numerous outliers. The large variation among outcomes hampered the analysis of the susceptibility in this group, while data on female workers was too scant for the analysis. Relationships exist between the impact of pesticides on performances and exposure duration. A change in test paradigms would help to decipher the impact more specifically. The use of biomarkers appropriate for lower exposures would allow a better prevention of neurotoxic effects due to occupational and environmental exposure. Intervention studies in adolescents seem warranted to specify their risk.

Health symptoms related to pesticide exposure and agricultural tasks among rice farmers from Northern Thailand

PURPOSE

The objective of this cross-sectional study was to investigate health symptoms related to occupational pesticide exposure and agricultural tasks in rice farmers.

METHODS

Data on demographic variables and health symptoms associated with pesticide exposure were collected from 182 rice farmers (exposed subjects) and 122 non-farmers (controlled group) using interviews and measuring whole blood acetylcholinesterase (AChE) activity during August and October 2012.

RESULTS

Rice farmers had a significantly lower median AChE activity than the controls (9,594 vs. 10,530 U/L, respectively) and a significantly higher prevalence of difficulty in breathing and chest pain [odds ratio (OR) 2.8, P < 0.01 and OR 2.5, P < 0.05, respectively]. The prevalence of dry throat and cramp was associated with those farmers who sprayed and mixed pesticides (OR 2.5 and 2.6 for dry throat, OR 2.5 and 2.9 for cramp, respectively; P < 0.01). The prevalence of numbness and diarrhea was associated with those farmers who scattered seed (OR 2.2, P < 0.01 and OR 3.6, P < 0.05, respectively). The prevalence of numbness and increasing anxiety was also associated with those farmers who harvested crops (OR 3.6, P < 0.01 and OR 3.0, P < 0.05, respectively).

CONCLUSIONS

Our findings suggest that occupational pesticide exposure and agricultural tasks in the paddy field may be associated with the increasing prevalence of respiratory tract and muscle symptoms. This possibility warrants further investigation in more detail.

Occupational pesticide exposures and respiratory health

Pesticides have been widely used to control pest and pest-related diseases in agriculture, fishery, forestry and the food industry. In this review, we identify a number of respiratory symptoms and diseases that have been associated with occupational pesticide exposures. Impaired lung function has also been observed among people occupationally exposed to pesticides. There was strong evidence for an association between occupational pesticide exposure and asthma, especially in agricultural occupations. In addition, we found suggestive evidence for a link between occupational pesticide exposure and chronic bronchitis or COPD. There was inconclusive evidence for the association between occupational pesticide exposure and lung cancer. Better control of pesticide uses and enforcement of safety behaviors, such as using personal protection equipment (PPE) in the workplace, are critical for reducing the risk of developing pesticide-related symptoms and diseases. Educational training programs focusing on basic safety precautions and proper uses of personal protection equipment (PPE) are possible interventions that could be used to control the respiratory diseases associated with pesticide exposure in occupational setting.

Adverse Impact of Insecticides on the Health of Palestinian Farm Workers in the Gaza Strip: A Hematologic Biomarker Study

To evaluate the health impact of insecticides on Palestinian farm workers in the Gaza Strip, the study assessed biomarkers in farm workers who used organophosphorus insecticides. Serum cholinesterase and complete blood count were determined before and after spraying of organophosphorus insecticides. Burning sensations in eyes/face (62.5%), itching/skin irritation (37.5%), and chest symptoms (29.2%) were reported. Serum butyrylcholinesterase (SBuChE) was significantly decreased at the end of the work day. Burning sensations in eyes/face and skin rash were significantly associated with inhibition of SBuChE activity (p < 0.05). Younger workers were more affected. Leukocyte and platelet counts were increased and hemoglobin decreased significantly, reflecting acute poisoning. Monitoring of SBuChE and hematologic parameters of farm workers could be useful to predict and prevent health hazards of pesticides.

Does farming have an effect on health status? A comparison study in west Greece

Investigating the health status of agricultural workers is a challenging goal. Contradictory outcomes concerning farmers' health are reported in the literature. In this cross-sectional study, certain clinical and neurobehavioral health outcomes were compared between farmers and non-farmers living in the same rural area. Farmers (328) and non-farmers (347), matched per age and sex, were selected randomly in an agricultural area in West Greece. Both groups underwent haematological and biochemical examinations and were administered two neurobehavioral tests, namely the Mini-Mental State Examination (MMSE) and the Montgomery-Åsberg Depression Rating Scale (MADRS). Sociodemographic, personal medical, nutritional and lifestyle data were recorded. According to personal statements, farmers suffered from hypertension, cardiovascular, orthopaedic and ENT problems in higher frequency. Haematocrit, haemoglobin and serum cholinesterase's activity were found to be lower among farmers. Lower prevalence of hypertension and better performances on MMSE and MADRS tests were recorded in young farmers in relation to young non-farmers, while these findings were reversed in older ages. Odds Ratios were calculated through multivariate logistic regression models. Factors affecting these impairments remain to be clarified.

Ocular toxicity from pesticide exposure: A recent review

Toxic effects on eyes result from exposure to pesticides via inhalation, ingestion, dermal contact and ocular exposure. Exposure of unprotected eyes to pesticides results in the absorption in ocular tissue and potential ocular toxicity. Recent literature on the risks of ocular toxicity from pesticide exposure is limited.Ocular toxicity from pesticide exposure, including the dose-response relationship, has been studied in different animal species. Cholinesterase enzymes have been detected in animal ocular tissue, with evidence of organophosphate-induced inhibition. Pathological effects of pesticides have been observed in conjunctiva, cornea, lens, retina and the optic nerve. Pesticide exposure has been associated with retinopathy in agricultural workers and wives of farmers who used pesticides. Saku disease, an optico-autonomic peripheral neuropathy, has been described in Japan in people living in an area where organophosphates were used. Pesticide exposure is also associated with abnormal ocular movements.Progressive toxic ocular effects leading to defective vision are a serious health concern. Agricultural workers are at high risk of exposure to pesticides and associated ocular toxicity. Primary prevention is the appropriate method of protecting eyes from pesticide-related damage. This includes improved eye safety and care in workplaces, and effective pesticide regulation for maintenance of public eye health.

Determination of acetylcholinesterase activity by the Ellman assay: a versatile tool for in vitro research on medical countermeasures against organophosphate poisoning

Inhibition of acetylcholinesterase (AChE) is the main mechanism of action of organophosphorus compounds (OP), and AChE reactivators (oximes) are at present the only causal therapeutic approach. Being the key target of OP toxicity, AChE may serve as a valuable tool for diagnosis of OP exposure as well as for the investigation of the kinetics of interactions between OP and oximes. At present, the rapid, simple, and cheap spectrophotometric Ellman assay is widely used for diagnosis, therapeutic monitoring and in vitro kinetic investigations. Application of the assay for investigation of the interactions between AChE, inhibitors, and oximes requires the consideration of potential matrix effects (e.g. hemoglobin), side reactions (e.g. oximolysis of substrate) and other determinants (e.g. pH, temperature). By taking these factors into account, the Ellman assay allows the precise and reproducible determination of kinetic constants as a basis for the understanding of toxic OP effects and for the development of improved therapies against poisoning by OP. In addition, advanced applications of the Ellman assay, for example, in a dynamic in vitro model for the real-time activity determination of membrane-bound AChE, enables the proper investigation of relevant tissue, primarily respiratory muscle, and extends the applicability of this method.

Oxidative stress in the blood of farm workers following intensive pesticide exposure

The aim of this study was to evaluate oxidative stress in workers who formulate organophosphate, synthetic pyrethroid and carbamate pesticides. In this survey, blood erythrocytes from a group of 94 pesticide-formulating workers (at least 5-years experience in pest-control in apple and cherry production) and 45 control subjects were examined for oxidative stress parameters. The control group was composed of 45 healthy people living in the same region with no exposure to pesticides. Lipid peroxidation level, catalase, superoxide dismutase and glutathione peroxidase activities in erythrocytes were analysed as biomarkers of oxidative stress. In addition, the acetylcholinesterase activity was measured as a biomarker of toxicity. Results indicated that chronic exposure to organophosphate, synthetic pyrethroid and carbamate pesticides were associated with increased activities of catalase, SOD and lipid peroxidation in erythrocytes (p < 0.05). Acetylcholinesterase activity did not show any significant differences between the two groups (p > 0.05). It is concluded that human chronic exposure to pesticides may result in stimulated antioxidant enzymes.

Prognostic value of long QT interval in acute and severe organophosphate poisoning

INTRODUCTION

Suicidal poisoning with organophosphorus (OP) pesticides is common, particularly from rural areas. This highlights the importance of determining an OP poisoning prognosis to decide how aggressive treatment should be. There are reports suggesting a relationship between prolonged corrected QT (QTC) interval and the severity of poisoning. We aimed to evaluate the prognostic utility of this clinical tool in OP poisoning (OPP) patients.

METHODS

Patients with the primary diagnosis of OPP who were admitted to the intensive care unit (ICU) of Loghman-Hakim Hospital Poison Centre (LHHPC) were the subjects of this prospective study. Cholinesterase (CE) activity and the QTC interval was determined for each patient using the Bazett formula and considering <440 msec as normal. Comparative outcomes of the study were duration of both hospitalization and mechanical ventilation, serum CE activity on admission and its daily level, total amount of atropine administered, analysis of the QT and QTC intervals in the primary ECG on admission and at the end of hospitalization, and rate of mortality.

RESULTS

The study included 42 patients with a diagnosis of OPP. The mean age of the patients was 32, ranged from 12 to 81 years old. The mortality rate was 37.5%. There was no significant difference between two groups (prolonged and normal QTC intervals) according to gender and age (p=.491 and p=.133, respectively). The CE level for long and normal QTC interval groups was 3.90+/-0.33 kU/L vs. 4.41+/-0.23 kU/L, respectively. The mortality rate in the long QTC group was significantly higher than that of the normal QTC group (p=.044). Moreover, the average period of hospitalization in patients with prolonged QTC interval was higher than the other group (p=.02). The average atropine required to control the muscarinic signs and symptoms such as salivation, bronchorrehea, and miosis in patients with prolonged QTC interval was 38.60 mg; in patients with normal QTC interval it was 20.02 mg (p=.013).

CONCLUSION

QTC interval prolongation may have prognostic value in OPP.

Cholinesterase activity, pesticide exposure and health impact in a population exposed to organophosphates

OBJECTIVE

Biological monitoring is an essential component for assessing the exposure of individuals to organophosphate pesticides. The aim of this study was to determine cholinesterase activity, pesticide exposure and health effects in the exposed population.

METHODS

A total of 90 individuals occupationally exposed to OPs and 30 controls were recruited in this study. Erythrocyte acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities were measured in two periods of low- and high-exposure.

RESULTS

There were statistically significant decrease in AChE and BuChE activities in the high-exposure period (20.73 +/- 0.99 U/gHb and 3.73 +/- 0.19 U/mL, respectively, P < 0.001) compared to the low-exposure period (29.81 +/- 1.19 U/gHb and 4.92 +/- 0.19 U/mL, respectively). All enzyme activities in the exposed group were statistically lower than in the control group. Analysis of the relation between cholinesterase activity and symptoms showed significant evidences.

CONCLUSIONS

The results suggested the association between occupational pesticide exposure and inhibition of cholinesterases. Thus, medical monitoring of cholinesterase inhibition and intervention programs regarding safety practices during field work are important issues aimed at minimizing adverse health effects of pesticide.

Trauma in Hispanic farm workers in Eastern North Carolina: 10-year experience at a level I trauma center

CONTEXT

In spite of the attention directed at the problem of occupational injuries within the farm environment and at the general health status of migrant farm workers in the United States, there have been no studies focusing on the risk for traumatic injury in general for this disadvantaged group.

PURPOSE

Trauma affecting Eastern North Carolina Hispanic farm workers was quantified and certain risk factors were found.

METHODS

Through chart review and retrieval of trauma registry information, patient occupational history, injury patterns, treatment variables as well as outcome and hospital charges were determined and compared with data for Hispanic construction workers and other service area males.

FINDINGS

Two hundred fifty-six Hispanic farm workers were admitted to the trauma center from July 1992 to June 2002, which is comparable to the risk (0.1%) of being admitted to the trauma center for an age-matched service area male. Only 5% of injuries occurred during farm work, 21% were penetrating injuries, and in 66% of cases (compared to 51% for other age-matched males) alcohol was involved.

CONCLUSION

Most trauma affecting Hispanic farm workers in Eastern North Carolina is not directly occupational and happens in conjunction with recreational activity, where alcohol is an important risk factor. The human and financial cost resulting from such injuries is of such magnitude that it deserves consideration by everybody who is involved in shaping policies in agriculture, immigration and rural public health.

Effects of occupational exposure in pesticide plant on workers' serum and erythrocyte cholinesterase activity

OBJECTIVES

The determination of cholinesterase activity has been commonly applied in the biomonitoring of exposure to organophosphates and carbamates and in the diagnosis of poisoning with anticholinesterase compounds. One of the groups who are at risk of pesticide intoxication are the workers engaged in the production of these chemicals.

AIMS

The aim of this study was to assess the effect of pesticides on erythrocyte and serum cholinesterase activity in workers occupationally exposed to these chemicals.

METHODS

The subjects were 63 workers at a pesticide plant. Blood samples were collected before they were employed (phase I) and after 3 months of working in the plant (phase II). Cholinesterase level in erythrocytes (EChE) was determined using the modified Ellman method, and serum cholinesterase (SChE) by butyrylthiocholine substrate assay.

RESULTS

The mean EChE levels were 48+/-11 IU/g Hb in phase I and 37+/-17 IU/g Hb in phase II (paired t-test, mean=-29; 95% CI=-43-14), p<0.001). The mean SChE level was 9569+/-2496 IU/l in phase I, and 7970+/-2067 IU/l in phase II (paired t-test, mean=1599; 95% CI=1140-2058, p<0.001). There was a significant increase in ALT level (p < 0.001) and a decrease in serum albumin level (p<0.001).

CONCLUSION

In view of the significant decrease in EChE and SChE levels among pesticide workers, it seems that routine assessment of cholinesterase level in workers employed in such occupations and people handling pesticides should be made obligatory.

Evaluation of a clinic-based cholinesterase test kit for the Washington State Cholinesterase Monitoring Program

BACKGROUND

The Washington State Cholinesterase Monitoring Program for pesticide handlers requires blood draws at local clinics, with samples tested at a central laboratory. At present, workers with inhibited cholinesterase activity may be re-exposed before they can be removed from work. In this study we explored the option of on-site testing at local clinics using the EQM Test-mate Kittrade mark, a portable cholinesterase test kit.

METHODS

Test kit cholinesterase activity measurements were performed on 50 blood samples by our research staff, and compared to measurements on the same samples by the Washington State Public Health Laboratory. Another set of samples was also analyzed with the test kit by medical staff at an eastern Washington clinic.

RESULTS

Triplicate measurements with the test kit had a 3.3% average coefficient of variation (CV) for plasma cholinesterase (PChE), and a 3.5% average CV for erythrocyte cholinesterase (AChE) measurements. The kit's PChE measurements were similar to PHL measurements (average ratio of 0.98) when performed in the laboratory, but had a tendency to underestimate activity when used in the clinic setting (average ratio of 0.87). The kit systematically overestimated AChE activity by 42-48% relative to the PHL measurements, regardless of where the samples were analyzed.

CONCLUSIONS

This easy-to-use test kit appeared to be a viable method for clinic-based PChE measurements, but was less consistent for AChE measurements performed in the clinic. Absolute measurements with the kit need to be evaluated carefully relative to standardized methods.

Plasma cholinesterase levels and health symptoms in peruvian farm workers exposed to organophosphate pesticides

The purpose of this study was to examine plasma cholinesterase (PChE) changes and the adverse health effects associated with chronic low-dose exposure to organophosphates (OPs) in a Peruvian agricultural population. A cross-sectional study with a clinical interview and blood tests was performed among 213 farm workers from two subtropical valleys in Peru. The control group consisted of 78 nonexposed workers from the same areas. PChE levels from the two exposed subgroups (pesticide applicators and other agricultural jobs) were significantly lower than those of controls (1554 +/- 315 U/l, 1532 +/- 340 U/l, and 1787 +/- 275 U/l, respectively). Fifteen percent of the exposed population reported a past poisoning by pesticides, all of them needing medical evaluation and treatment. They had significantly lower PChE levels as compared to those without this antecedent. Approximately 61% of the exposed workers reported pesticide-related symptoms, but no significant difference was found in their PChE as compared to workers without symptoms. On the other hand, the use of personal protective equipment (PPE) was significantly associated with higher PChE levels and with a lower risk of reporting pesticide-related symptoms, which supports the benefit from using appropriate protective measures. In conclusion, data indicate that farm workers exposed to OPs in developing countries need to be monitored by means of PChE and an examination of their clinical status, which would allow identification of farm workers most at risk from pesticide toxicity. The use of correct PPE is highly recommended.

[3H] Citalopram Binding to Serotonin Transporter Sites in Minnow Brains

Mammalian serotonin (SERT) and norepinephrine transporters (NET) are target sites for antidepressants and are affected by pesticide exposures. Herein, we examined whether golden shiner (Notemigonus crysoleucas) or fathead minnow (Pimphales promelas) SERTs and catecholamine transporters respond comparably to mammalian SERTs and NETs. We compared the pharmacological profiles of central SERT and NET binding sites of the golden shiner minnow to those of rats. Homogenate binding with the radioligand [(3)H] citalopram indicated that golden shiner SERT has a K(D) of 7 +/- 3 nM and a B(max) of 226 +/- 46 fmol/mg protein. These values are similar to those of rat cortical SERT (K(D) 1.4 +/- 0.1 nM and B(max) 240 +/- 48 fmol/mg protein). We also examined SERT binding in fathead minnow brain, and found it similar to that of the golden shiner. A putative golden shiner NET, measured using [(3)H] nisoxetine, had K(D) = 12 +/- 5 nM and B(max) = 187 +/- 49 fmol/mg protein, whereas rat hippocampal NET had K(D) = 5 +/- 2 nM and B(max) = 93 +/- 8 fmol/mg protein. Minnow SERT and NET binding is displaceable by selective reuptake inhibitors. Finally, we exposed zebrafish (Danio rerio) to the serotonin reuptake inhibiting antidepressant sertraline or the organophosphate chlorpyrifos for 21 days. After either treatment, SERT binding was reduced by 50% (n = 3-6, P < 0.05). In summary, minnow central SERT and NET express slightly lower affinity for antidepressants than rats. However, magnitudes of affinity are similar, and minnow SERT binding is decreased by chronic sertraline or chlorpyrifos administration.

Acute symptoms following work with pesticides

BACKGROUND

Serious accidental poisoning by pesticides is rare in the UK, but more minor pesticide-related illness may be under-reported. Anecdotally, use of sheep dip has been linked with flu-like symptoms.

AIM

To explore the frequency, nature and determinants of acute symptoms following work with pesticides.

METHODS

A postal survey of men in three rural areas of England and Wales provided data on occupational use of five categories of pesticide, occurrence of 12 specified symptoms within 48 h of using pesticides and tendency to somatize. Risk factors for pesticide-related symptoms were assessed by modified Cox regression.

RESULTS

Of 10 765 responders (response rate = 31%), 4108 had at some time used pesticides occupationally, including 935 (23%) who reported symptoms following such work on at least one occasion. In two areas, acute symptoms were most frequent following use of sheep dip (29 and 32% of users), but in the third area the rate was significantly lower (13% of users). The relative frequency of symptoms was similar for all five categories of pesticide, and flu-like symptoms did not cluster unusually among users of sheep dip. Risk of pesticide-related symptoms increased with somatizing tendency (prevalence ratio for highest versus lowest category 2.4, 95% confidence interval 2.0-3.0) and was higher in men who had used pesticides most often or handled concentrate.

CONCLUSION

Acute symptoms are common following work with pesticides, but in many cases the illness may arise through psychological rather than toxic mechanisms.

Paraoxonase (PON1) polymorphism and activity as the determinants of sensitivity to organophosphates in human subjects

Paraoxonase (PON1) plays an important role in mechanism of organophosphorus compound (OP) toxicity, as seen both in vitro and in vivo studies. Polymorphisms of PON1 gene at coding and promoter regions have also been to affect on the hydrolytic activity and PON1 level. The objectives of this study were to determine PON1 polymorphism and activity in an OP-exposed population and the effects on inhibition of cholinesterase activity. The studied population consisted of control (n=30) and exposed groups (n=90). All enzyme activities (AChE, BuChE, paraoxonase, arylesterase and diazonase) were measured once for control group and two periods of exposure for exposed group. Three polymorphisms of PON1 (Q192R, L55M and T-108C) were identified only in the exposed subjects. The results demonstrated that AChE activity in both high (345.5 microkat/gHb) and low exposure periods (496.9 microkat/gHb) of the exposed group were significantly different from control group (649.7 microkat/gHb, p<0.01). For BuChE activity, the exposed group also showed the statistically lower level in both periods (high exposure period: 62.17 microkat/L and low exposure period: 81.84 microkat/L) than those in the control group (93.35 microkat/L). Serum paraoxonase activity was significantly different among individual genotypes, RR>QR>RR, LL>LM and -108CC>-108CT>-108TT, but this was not found for those of arylesterase and diazonase activities. Q192R and L55M as well as Q192R and T-108C also presented substantial linkage disequilibrium. Further analysis was performed with haplotypes and various enzyme activities. AChE activity was not affected by haplotypes. Individuals with "211" haplotype showed significantly higher paraoxonase activity and BuChE activity than other haplotypes but not in diazonase activity. In conclusion, PON1 gene exhibited a wide variation in enzyme activities both within and between genotypes which implied insights of a potentially difference in sensitivity to OP toxicity.

Neurologic symptoms in licensed pesticide applicators in the Agricultural Health Study

Exposure to high levels of many pesticides has both acute and long-term neurologic consequences, but little is known about the neurotoxicity of chronic exposure to moderate pesticide levels. We analysed cross-sectional data from 18 782 Caucasian, male, licensed pesticide applicators, enrolled in the Agricultural Health Study from 1993 to 1997. Applicators provided information on lifetime pesticide use, and 23 neurologic symptoms typically associated with pesticide intoxication. Increased risk of experiencing >/=10 symptoms during the year before enrollment was associated with cumulative pesticide use, personally mixing or applying pesticides, pesticide-related medical care, diagnosed pesticide poisoning, and events involving high personal pesticide exposure. Greatest risk was associated with use of organophosphate and organochlorine insecticides. Results were similar after stratification by pesticide use during the year before enrollment, or exclusion of applicators with a history of pesticide poisoning, or high-exposure events. Use of pesticide application methods likely to involve high personal exposure was associated with greater risk. Groups of symptoms reflecting several neurologic domains, including affect, cognition, autonomic and motor function, and vision, were also associated with pesticide exposure. These results suggest that neurologic symptoms are associated with cumulative exposure to moderate levels of organophosphate and organochlorine insecticides, regardless of recent exposure or history of poisoning.

Studying health outcomes in farmworker populations exposed to pesticides

A major goal of studying farmworkers is to better understand how their work environment, including exposure to pesticides, affects their health. Although a number of health conditions have been associated with pesticide exposure, clear linkages have yet to be made between exposure and health effects except in cases of acute pesticide exposure. In this article, we review the most common health end points that have been studied and describe the epidemiologic challenges encountered in studying these health effects of pesticides among farmworkers, including the difficulties in accessing the population and challenges associated with obtaining health end point data. The assessment of neurobehavioral health effects serves as one of the most common and best examples of an approach used to study health outcomes in farmworkers and other populations exposed to pesticides. We review the current limitations in neurobehavioral assessment and strategies to improve these analytical methods. Emerging techniques to improve our assessment of health effects associated with pesticide exposure are reviewed. These techniques, which in most cases have not been applied to farmworker populations, hold promise in our ability to study and understand the relationship between pesticide exposure and a variety of health effects in this population. Key words: biomarkers, cancer, epidemiology, health outcomes, immigrants, neurobehavioral, neuropathy, pesticides.

Preventing occupational exposure to pesticides: using participatory research with latino farmworkers to develop an intervention

Pesticide exposure is an occupational health hazard for migrant farmworkers. The US-EPA Worker Protection Standard (WPS) mandates training programs to prevent or reduce exposure. WPS implementation in a local context requires understanding individual, workplace, and community environmental factors that lead to exposure and influence intervention effectiveness. Participatory research within the PRECEDE-PROCEED planning framework was used to design a WPS training program for Mexican farmworkers in North Carolina cucumber and tobacco production. Research with farmworkers, farmers, health care providers, and Cooperative Extension agents identified modifiable behaviors and environmental factors, as well as structural and regulatory barriers requiring intervention. Data were gathered and analyzed through individual and group interviews, community forums, an advisory board, and a partnership between academic researchers and a community-based organization. The intervention's dominant features are (a) focus on key health behaviors, (b) relevance to local conditions, and (c) attention to issues of control in the workplace. Participatory research is effective for designing a health intervention where diverse social, cultural, political, and regulatory issues affect farmworkers' risk of exposure.

Neurologic symptoms in licensed private pesticide applicators in the agricultural health study

Exposure to high levels of many pesticides has both acute and long-term neurologic consequences, but little is known about the neurotoxicity of chronic exposure to moderate levels of pesticides. We analyzed cross-sectional data from 18,782 white male licensed private pesticide applicators enrolled in the Agricultural Health Study in 1993-1997. Applicators provided information on lifetime pesticide use and 23 neurologic symptoms typically associated with pesticide intoxication. An indicator of more symptoms (> or = 10 vs. < 10) during the year before enrollment was associated with cumulative lifetime days of insecticide use: odds ratios (95% confidence intervals) were 1.64 (1.36-1.97) for 1-50 days, 1.89 (1.58-2.25) for 51-500 days, and 2.50 (2.00-3.13) for > 500 days, compared with never users. A modest association for fumigants [> 50 days, 1.50 (1.24-1.81)] and weaker relationships for herbicides [> 500 days, 1.32 (0.99-1.75)] and fungicides [> 50 days, 1.23 (1.00-1.50)] were observed. Pesticide use within the year before enrollment was not associated with symptom count. Only associations with insecticides and fumigants persisted when all four pesticide groups were examined simultaneously. Among chemical classes of insecticides, associations were strongest for organophosphates and organochlorines. Associations with cumulative exposure persisted after excluding individuals who had a history of pesticide poisoning or had experienced an event involving high personal pesticide exposure. These results suggest that self-reported neurologic symptoms are associated with cumulative exposure to moderate levels of fumigants and organophosphate and organochlorine insecticides, regardless of recent exposure or history of poisoning.

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.

Association of pesticide exposure with neurologic dysfunction and disease

Poisoning by acute high-level exposure to certain pesticides has well-known neurotoxic effects, but whether chronic exposure to moderate levels of pesticides is also neurotoxic is more controversial. Most studies of moderate pesticide exposure have found increased prevalence of neurologic symptoms and changes in neurobehavioral performance, reflecting cognitive and psychomotor dysfunction. There is less evidence that moderate exposure is related to deficits in sensory or motor function or peripheral nerve conduction, but fewer studies have considered these outcomes. It is possible that the most sensitive manifestation of pesticide neurotoxicity is a general malaise lacking in specificity and related to mild cognitive dysfunction, similar to that described for Gulf War syndrome. Most studies have focused on organophosphate insecticides, but some found neurotoxic effects from other pesticides, including fungicides, fumigants, and organochlorine and carbamate insecticides. Pesticide exposure may also be associated with increased risk of Parkinson disease; several classes of pesticides, including insecticides, herbicides, and fungicides, have been implicated. Studies of other neurodegenerative diseases are limited and inconclusive. Future studies will need to improve assessment of pesticide exposure in individuals and consider the role of genetic susceptibility. More studies of pesticides other than organophosphates are needed. Major unresolved issues include the relative importance of acute and chronic exposure, the effect of moderate exposure in the absence of poisoning, and the relationship of pesticide-related neurotoxicity to neurodegenerative disease.

Health Effects of Chronic Pesticide Exposure: Cancer and Neurotoxicity

Pesticides are widely used in agricultural and other settings, resulting in continuing human exposure. Epidemiologic studies indicate that, despite premarket animal testing, current exposures are associated with risks to human health. In this review, we describe the routes of pesticide exposures occurring today, and summarize and evaluate the epidemiologic studies of pesticide-related carcinogenicity and neurotoxicity in adults. Better understanding of the patterns of exposure, the underlying variability within the human population, and the links between the animal toxicology data and human health effects will improve the evaluation of the risks to human health posed by pesticides. Improving epidemiology studies and integrating this information with toxicology data will allow the human health risks of pesticide exposure to be more accurately judged by public health policy makers.

Neurobehavioral performance and work experience in Florida farmworkers

Farmworkers experience many work-related hazards, including exposure to neurotoxicants. We compared neurobehavioral performance of 288 farmworkers in central Florida who had done farm work for at least 1 month with 51 controls who had not. Most of the farmworkers had worked in one or more of three types of agriculture: ornamental ferns, nurseries, or citrus fruit. We collected information on farm work history in a structured interview and evaluated neurobehavioral performance using a battery of eight tests. Analyses were adjusted for established confounders including age, sex, education, and acculturation. Ever having done farm work was associated with poor performance on four tests--digit span [odds ratio (OR) = 1.90; 95% confidence interval (CI), 1.02-3.53], tapping (coefficient = 4.13; 95% CI, 0.00-8.27), Santa Ana test (coefficient = 1.34; 95% CI, 0.29-2.39), and postural sway (coefficient = 4.74; 95% CI, -2.20 to 11.7)--but had little effect on four others: symbol digit latency, vibrotactile threshold, visual contrast sensitivity, and grip strength. Associations with farm work were similar in magnitude to associations with personal characteristics such as age and sex. Longer duration of farm work was associated with worse performance. Associations with fern work were more consistent than associations with nursery or citrus work. Deficits related to the duration of work experience were seen in former as well as current farmworkers, and decreased performance was related to chronic exposure even in the absence of a history of pesticide poisoning. We conclude that long-term experience of farm work is associated with measurable deficits in cognitive and psychomotor function.

Neurological symptoms among Sri Lankan farmers occupationally exposed to acetylcholinesterase-inhibiting insecticides

BACKGROUND

In many agricultural districts in Sri Lanka, pesticide poisoning is a leading cause of death. This study aims to evaluate the impact of pesticide use on Sri Lankan farmers' health.

METHODS

A total of 260 subjects were surveyed in both a low and a high exposure period. Acetylcholinesterase activity was measured and data on symptoms were collected with questionnaires.

RESULTS

Twenty-four percent of surveyed farmers had suffered at least once from acute pesticide poisoning. Farmers showed significantly more inhibition of cholinesterase activity than controls. Acute symptoms indicative for exposure to cholinesterase-inhibiting pesticides were associated with farming and a higher degree of cholinesterase suppression (more than 13% inhibition). Integrated Pest Management (IPM) training seemed to result in less insecticide use, and less cholinesterase inhibition.

CONCLUSIONS

Our results suggest that occupational acetylcholinesterase-inhibiting insecticide exposures have a negative impact on Sri Lankan farmers' health. Overall reduction in pesticide use seems the best option to protect farmers from the adverse effects of pesticides.

Mortality of mental disorders in relation to potential pesticide exposure

Some studies have suggested a role of pesticide exposure in the development of neurobehavioral disorders. This case-control study examined the association between mortality from mental disorders and occupational exposure to pesticides. The study population consisted of 7756 deaths and 330,452 eligible controls identified from US death certificate files for the years 1988 through 1992. Exposure assignment was based on job title reported on the death certificates. Employment in jobs potentially involving pesticide exposure was weakly associated with the risk of death from mental disorders (odds ratio [OR] = 1.46; 95% confidence interval (95% CI) = 1.33-1.60). This association was stronger among women (OR = 2.65; 95% CI = 1.89-3.71), in particular for deaths from neurotic disorders (OR = 4.32; 95% CI = 2.44-7.64). These results must be interpreted with caution, however, because the impact of social and work-related factors other than pesticide exposure is not known.

Pesticide take-home pathway among children of agricultural workers: study design, methods, and baseline findings

Farmworkers are exposed to pesticides and may take home pesticide residues to their families. In this paper, self-reported pesticide exposure and home practices to reduce the amount of pesticide residues taken home were examined among 571 farmworkers. Urine samples from a subsample of farmworkers and children and dust samples from households and vehicles also assessed pesticide exposure. Overall, 96% of respondents reported exposure to pesticides at work. Many employers did not provide resources for hand washing. Farmworkers' protective practices to keep pesticide residues out of the home were at a low level. In a subset of respondents, pesticide levels above the limit of quantitation were seen in the urine of children and adults and in house and vehicle dust. The results support the take-home pathway of pesticide exposure. Ways must be found to reduce this pesticide exposure among children of farmworkers.