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.     

Prenatal exposure to pesticides: a feasibility study among migrant and seasonal farmworkers.

BACKGROUND: Migrant and seasonal farmworkers have a high potential for pesticide exposures, yet are rarely included in epidemiologic studies. This study examined the feasibility of assessing prenatal exposures to pesticides and other compounds in pregnant Hispanic farmworkers. METHODS: Nine women completed a survey about work experiences during pregnancy. Maternal urine, cord blood, and placenta samples were obtained at delivery for analysis of 51 analytes, including 6 phenoxy acid or triazine herbicides, 21 organochlorine insecticides, 10 PCBs, and 14 volatile organic compounds. RESULTS: Seven of 51 analytes were found in the biological samples. DDE, DDT, dichlorbenzene, toluene, trimethylbenzene, and endosulfan sulfate were detected in cord blood samples, and 2,4-D in urine from one or more women. CONCLUSIONS: We documented the feasibility of following farmworkers to assess in utero exposure to pesticides and other contaminants, and demonstrated exposure to these compounds. Difficulties in measuring pesticides with short half lives were noted.     

Prenatal exposure to organophosphate pesticides and IQ in 7-year-old children

Context: Organophosphate (OP) pesticides are neurotoxic at high doses. Few studies have examined whether chronic exposure at lower levels could adversely affect children’s cognitive development.Objective: We examined associations between prenatal and postnatal exposure to OP pesticides and cognitive abilities in school-age children.Methods: We conducted a birth cohort study (Center for the Health Assessment of Mothers and Children of Salinas study) among predominantly Latino farmworker families from an agricultural community in California. We assessed exposure to OP pesticides by measuring dialkyl phosphate (DAP) metabolites in urine collected during pregnancy and from children at 6 months and 1, 2, 3.5, and 5 years of age. We administered the Wechsler Intelligence Scale for Children, 4th edition, to 329 children 7 years of age. Analyses were adjusted for maternal education and intelligence, Home Observation for Measurement of the Environment score, and language of cognitive assessment.Results: Urinary DAP concentrations measured during the first and second half of pregnancy had similar relations to cognitive scores, so we used the average of concentrations measured during pregnancy in further analyses. Averaged maternal DAP concentrations were associated with poorer scores for Working Memory, Processing Speed, Verbal Comprehension, Perceptual Reasoning, and Full-Scale intelligence quotient (IQ). Children in the highest quintile of maternal DAP concentrations had an average deficit of 7.0 IQ points compared with those in the lowest quintile. However, children’s urinary DAP concentrations were not consistently associated with cognitive scores.Conclusions: Prenatal but not postnatal urinary DAP concentrations were associated with poorer intellectual development in 7-year-old children. Maternal urinary DAP concentrations in the present study were higher but nonetheless within the range of levels measured in the general U.S. population.     

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

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

Effects of occupational exposure to organophosphate pesticides on nerve and neuromuscular function

This study aimed to investigate whether occupational exposure to organophosphate (OP) pesticides caused neurophysiological abnormalities. Thirty farmers who regularly spray OP pesticides and 30 fishermen (controls), living close by but not involved in pesticide spraying, were evaluated during and between cultivation seasons. The farmers had higher erythrocyte acetylcholinesterase levels than the controls during (P = 0.06) and between cultivation seasons (P = 0.09). During the cultivation season, there was a significant reduction in erythrocyte acetylcholinesterase activity in both groups (P < 0.01). Significant differences between the farmers and controls were found in sensory conduction velocity (P = 0.04) and motor conduction velocity (P = 0.04) between cultivation seasons. Sensory conduction velocity was reduced significantly in farmers (P < 0.01) and in controls (P = 0.04) during the cultivation season. Effects of OP poisoning were seen both in farmers and in controls, who had no history of spray activities. Evidence of sensory dysfunction after acute exposure and sensory and motor impairment after long-term low-level exposure to OP was seen.     

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.     

Agricultural exposure to carbamate pesticides and risk of non-Hodgkin lymphoma

Recent epidemiological studies have suggested an increased risk of non-Hodgkin lymphoma (NHL) from carbamate insecticide use among farmers. To further explore the possible relationships, we conducted a pooled analysis of three population-based case-control studies conducted in four midwestern states in the United States. A total of 985 white male subjects and 2895 control subjects were included in this analysis. Unconditional logistic regression was used to estimate the association and control for confounding. Compared with nonfarmers, farmers who had ever used carbamate pesticides had a 30% to 50% increased risk of NHL, whereas farmers without carbamate pesticide use showed no increased risk. Analyses for individual carbamate pesticides found a more consistent association with Sevin but not carbofuran, butylate, or S-ethyl dipropylthiocarbamate plus protectant. Among farmers using Sevin, the risk of NHL was limited to those who personally handled the product, those who first used the product for > or = 20 years before their disease diagnosis, and those who used the product for a longer period. These associations persisted after adjusting for other major classes of pesticides. These results suggest an increased risk of NHL associated with carbamate pesticide use, particularly Sevin. Further investigation of the association is warranted.     

A pilot study of maternal exposure to organophosphate pesticides and newborn neurodevelopment in Thailand

The objective of this study was to evaluate whether prenatal exposures to organophosphate (OP) pesticides from maternal agricultural use are associated with neonatal neurobehavioral effects. A pilot study conducted in three provinces in Thailand measured maternal urinary metabolites of OP pesticides in pregnant women at 7 months gestation and at birth. Within 3 days of birth, 82 newborns underwent neurobehavioral testing using the Brazelton Neonatal Behavioral Assessment Scale (NBAS). Comparison of the NBAS test results with maternal OP metabolite levels found the neonates NBAS Habituation cluster score increased with maternal dimethylphosphate (DMP) levels (p = 0.04) while the Range of State score increased with total diethylphosphate (DEP) levels (p = 0.01). The Number of Abnormal Reflexes in the neonate also increased as maternal urinary total DEP levels increased (p = 0.06). These preliminary findings suggest that pre-natal exposures to OP pesticides can impact newborn neurodevelopment and support the need for a longitudinal evaluation of childhood neurodevelopment in relation to pesticide exposures in Thailand.     

Occupational exposure to pesticides and nerve conduction studies among Korean farmers

This study aimed to determine whether occupational exposure to pesticides was associated with decreased nerve conduction studies among farmers. On 2 separate occasions, the authors performed a cross-sectional study of a group of 31 male farmers who periodically applied pesticides. The study included questionnaire interviews and nerve conduction studies on the median, ulnar, posterior tibial, peroneal, and sural nerves. Although all mean values remained within laboratory normal limits, significant differences between the first and second tests were found in sensory conduction velocities on the median and sural nerves, and motor conduction velocities on the posterior tibial nerve. Lifetime days of pesticide application was negatively associated with nerve conduction velocities at most nerves after adjusting for potential confounders. These findings may reflect a link between occupational pesticide exposure and peripheral neurophysiologic abnormality that deserves further evaluation.     

Chronic exposure to organophosphate (OP) pesticides and neuropsychological functioning in farm workers: a review

Background: Previous studies have demonstrated that acute poisoning from exposure to organophosphate (OP) pesticides in agricultural workers causes adverse health effects. However, neuropsychological and cognitive effects of chronic occupational exposure to OP pesticides remain controversial.

Objective: To identify, evaluate, and systematize existing evidence regarding chronic exposure to OP pesticides and neuropsychological effects in farmworkers.

Methods: Using the PubMed search engine, a systematic review process was implemented and replicated according to the PRISMA statement. Eligibility criteria included workers over 18 years of age exposed to OP pesticides as well as assessment of neuropsychological and cognitive functioning. Search terms were in English and Spanish languages and included organophosphate and workers.

Results: Of the search results, 33 of 1,256 articles meet eligibility criteria. Twenty-four studies found an association between chronic occupational exposure to OP pesticides and low neuropsychological performance in workers. We classified nine of the studies to have study design limitations. Studies indicated occupational exposure to OP pesticides is linked to difficulties in executive functions, psychomotor speed, verbal, memory, attention, processing speed, visual–spatial functioning, and coordination. Nine studies find no relationship between OP pesticides exposure and neuropsychological performance.

Conclusions: Overall, evidence suggests an association between chronic occupational exposure to OP pesticides and neuropsychological effects. However, there is no consensus about the specific cognitive skills affected.     

Pesticide exposure beliefs among Latino farmworkers in North Carolina's Christmas tree industry

BACKGROUND: Pesticide exposure is a major preventable occupational hazard for farmworkers. This study examined the beliefs of Latino farmworkers in North Carolina's Christmas tree industry regarding pesticide exposure. METHODS: In-depth interviews were conducted with 20 Mexican male seasonal farmworkers. Participants discussed beliefs about agricultural chemicals, routes of exposure, and health effects of these chemicals. They also discussed their knowledge and use of pesticide safety practices and safety training received. RESULTS: Most farmworkers knew that pesticides could be harmful, though workers varied in their levels of knowledge regarding routes of exposure, specific health effects of pesticides, and ways to avoid and reduce exposure. Workers varied considerably in the amount of safety training received and use of safety practices. Perceived lack of control and health beliefs were salient factors that decreased workers' use of safety practices. CONCLUSIONS: This study adds to the growing body of research which documents the health beliefs of Latino farmworkers in the U.S. relative to pesticides and pesticide safety. This literature is beginning to show convergence on several points (e.g., farmworker knowledge of acute vs. long-term illness resulting from pesticide exposure), as well as regional variation in pesticide safety beliefs. This study substantiates the need for pesticide safety education to address issues of control as well as beliefs.     

Community-based intervention to reduce pesticide exposure to farmworkers and potential take-home exposure to their families

The US EPA Worker Protection Standard requires pesticide safety training for farmworkers. Combined with re-entry intervals, these regulations are designed to reduce pesticide exposure. Little research has been conducted on whether additional steps may reduce farmworker exposure and the potential for take-home exposure to their families. We conducted an intervention with 44 strawberry harvesters (15 control and 29 intervention group members) to determine whether education, encouragement of handwashing, and the use of gloves and removable coveralls reduced exposure. Post-intervention, we collected foliage and urine samples, as well as hand rinse, lower-leg skin patch, and clothing patch samples. Post-intervention loading of malathion on hands was lower among workers who wore gloves compared to those who did not (median=8.2 vs. 777.2 microg per pair, respectively (P<0.001)); similarly, median MDA levels in urine were lower among workers who wore gloves (45.3 vs. 131.2 microg/g creatinine, P<0.05). Malathion was detected on clothing (median=0.13 microg/cm(2)), but not on skin. Workers who ate strawberries had higher malathion dicarboxylic acid levels in urine (median=114.5 vs. 39.4 microg/g creatinine, P<0.01). These findings suggest that wearing gloves reduces pesticide exposure to workers contacting strawberry foliage containing dislodgeable residues. Additionally, wearing gloves and removing work clothes before returning home could reduce transport of pesticides to worker homes. Behavioral interventions are needed to reduce consumption of strawberries in the field.     

Work with pesticides and organophosphate sheep dips

Pesticides are an important hazard in agriculture. In developed countries their use is strictly regulated. Risk assessment for new pesticides includes comparison of the potential exposures of spray operators and other farm workers with a reference value. Usually, this is derived from toxicological studies in animals with allowance for the uncertainties in extrapolating between and within species. Older pesticides undergo periodic reviews, for which epidemiological data may also be available. Unintentional fatal poisoning by pesticides is extremely rare in Britain. Documented reports of non-fatal acute poisoning are also uncommon, but there may be substantial under-ascertainment of minor incidents. Pesticides have been linked with various chronic diseases, but few associations have been clearly established. A particular concern recently in Britain has been the possibility that organophosphate insecticides can cause chronic neuropsychiatric illness.