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Methyl parathion (Me-Pa) is an oxidizing organophosphate (OP) pesticide that generates reactive oxygen species (ROS) through its biotransformation. Some studies have also suggested that OP pesticides have the capacity to alkylate biomolecules, including DNA. In general, DNA methylation in gene promoters represses transcription. NRF2 is a key transcription factor that regulates the expression of antioxidant, metabolic and detoxifying genes through the antioxidant response element (ARE) situated in promoters of regulated genes. Furthermore, DNA repair genes, including 8-oxoguanine DNA glycosidase (OGG1), have been proposed as NRF2 target genes. Me-Pa exposure produces poor semen quality, genetic and oxidative damage in sperm cells, and reduced fertility. However, the Me-Pa effects on the methylation status and the expression of antioxidant (Nrf2) or DNA repair (Ogg1) genes in male germ cells have not been investigated. Therefore, mice were exposed to Me-Pa to evaluate the global (%5-mC) and specific methylation of Nrf2 and Ogg1 genes using pyrosequencing, gene expression, and total protein carbonylation in male germ cells. The results showed that Me-Pa significantly decreased the global DNA methylation pattern and significantly increased the methylation of two CpG sites within Ogg1 promoter and one CpG site within Nrf2 promoter. In addition, Ogg1 or Nrf2 expression did not change after Me-Pa exposure despite the oxidative damage produced. Altogether, our data suggest that Me-Pa toxicity alters Ogg1 and Nrf2 promoter methylation in male germ cells that may be modulating their gene expression., (Copyright © 2018. Published by Elsevier Inc.)

The effects of contamination, through water or food, of a sublethal dose of the organophosphate methyl parathion were analyzed in tissues that are responsible for absorption (gills, intestine) and metabolism (liver), in the freshwater fish Corydoras paleatus. In gill respiratory lamellae, epithelial hyperplasia, edema, and detachment occurred, diminishing sooner after contamination by food than after contamination through water. In the intestine, lipoid vacuolization of enterocytes, apical cytoplasm, and an increase in goblet cell activity occurred mainly after ingestion of contaminated food. The liver exhibited cloudy swelling, bile stagnation, focal necrosis, atrophy, and vacuolization after contamination through both absorption routes, the highest degeneration being between T(8) and T(24). Metabolic processes that depend on liver function were equally impaired by the two routes of contamination, but secondary effects vary with gill and intestine pathologies as a consequence of water and food contamination, respectively. Therefore, a "safe" sublethal dose of methyl parathion causes serious health problems in C. paleatus.

In November 1994 methyl parathion (MP), a restricted agricultural pesticide, was discovered to have been illegally sprayed within hundreds of residences in Lorain County, Ohio. Surface levels and air concentrations of MP revealed detectable levels of the pesticide 3 years after spraying. Because of the high toxicity of MP (lethal dose to 50% of rats tested [LD50] = 15 mg/kg) and long half-life indoors, risk-based relocation and decontamination criteria were created. Relocation criteria were derived based on levels of p-nitrophenol in urine, a metabolic byproduct of MP exposure. In Ohio, concentrations of MP on surfaces and in the air were also used to trigger relocations. The criteria applied in Ohio underwent refinement as cases of MP misuse were found in Mississippi and then in several other states. The MP investigation (1994-1997) was the largest pesticide misuse case in the nation, ultimately involving the sampling of 9,000 residences and the decontamination of 1,000 properties. This article describes the methodology used for relocation of residents and decontamination of properties having MP.

In Lorain County, Ohio, unexplained infant deaths in homes sprayed with methyl parathion (MP), an organophosphate (OP) pesticide, prompted an investigation to determine whether infants living in treated homes are at higher risk for unexplained death. A case was defined as any death of an infant (12 months of age) in Lorain County between 1 January 1990 and 31 December 1994, attributed to sudden infant death syndrome (SIDS) or other unknown natural causes. For each case infant, birth certificate data were used to identify two control infants matched with regard to date of birth, sex, city of residence, and maternal race and educational level. Wipe samples from the home address listed on the birth certificate of control infants or the death certificate of case infants were analyzed for MP. Birth certificates provided additional risk factor information. The relationship between MP contamination and unexplained death was analyzed by exact conditional logistic regression. Wipe samples were collected from the residences of 34 case infants and 72 control infants. MP (>0.02 mg/100 cm2) was detected in five homes, three of which had been occupied by case infants. Case infants were 4.6 times more likely than control infants to have lived in MP-treated homes, but the confidence interval (CI) was wide (95% CI: 0.2, 274.7) and included 1. Maternal smoking, young maternal age, and the presence of other siblings in the family were each independently predictive of case status. In a multivariate model adjusting for these other variables and the matching variables, the estimated risk associated with MP exposure was 13.0 (95% CI: 0.2, 2,685.0). Although this association was not statistically significant and should be interpreted cautiously, it suggests an increased risk for unexplained death among infants living in MP-contaminated homes. The relationship between children's health and exposure to OP pesticides including MP should be evaluated further.

In January 1995 the U.S. Environmental Protection Agency declared methyl parathion-contaminated homes in Lorain County, Ohio, as a Superfund cleanup site. During the 2-year cleanup, the Centers for Disease Control and Prevention in collaboration with county and city health officials conducted a study of exposure and health effects among residents. We administered 254 household and 747 individual questionnaires; urine analysis for p-nitrophenol (PNP, a metabolite of methyl parathion) was available for 626 participants. We also reviewed medical records of 49 people who were hospitalized or died after their homes were sprayed. People living in homes sprayed <180 days previously were most likely to have the highest PNP levels (22.9% > 100 ppb PNP), but even people living in homes sprayed more than a year previously appeared to be highly exposed (8.5% > 100 ppb PNP). The National Health and Nutrition Examination Survey reference range is 0-63 ppb. Median detectable PNP levels among children younger than 3 years of age were 93.9 ppb compared with 41.6 ppb among people older than 3 years. Younger children appeared to be at greatest risk of exposure. In none of the medical records that we reviewed did a health care provider consider pesticide poisoning as a potential etiology.

In the fall of 1994, Lorain County, Ohio, became the site of the first investigation of several large-scale incidences in which the organophosphate pesticide methyl parathion was illegally applied to private residences. The extent of potential human exposure to this pesticide led the Ohio Department of Health to formally request technical assistance from the Centers for Disease Control and Prevention (CDC). This article describes the initial investigation of 64 homes in Ohio and introduces the method of using both biological markers of exposure (p-nitrophenol levels in human urine samples) and environmental markers of contamination in dust and air samples when making public health decisions about the cleanup of homes sprayed with methyl parathion. The results of the CDC rapid investigation led the U.S. Environmental Protection Agency to declare the contaminated homes in Lorain County a Superfund cleanup site. Seven years after the Lorain incident, and after subsequent Superfund actions had been implemented in Illinois and Mississippi, researchers participated in an expanded session devoted to methyl parathion at the 11th Annual Meeting of the International Society of Exposure Analysis held in Charleston, South Carolina, in the fall of 2001. The articles included in this monograph are based on presentations at that meeting. They report previously unpublished data that tell the methyl parathion story from different perspectives, each providing in-depth information about separate aspects of this multistate, multiagency, and multimillion dollar chemical exposure. This monograph is the methyl parathion story.

Methyl parathion (MP), an organophosphate pesticide, was sprayed illegally for pest control in U.S. residences and businesses in Mississippi and Ohio. To evaluate the association between MP exposure and neurobehavioral development, children 6 years of age or younger at the time of the spraying and local comparison groups of unexposed children were assessed using the pediatric environmental neurobehavioral test battery (PENTB). The PENTB is composed of informant-based procedures (parent interview and questionnaires) and performance-based procedures (neurobehavioral tests for children 4 years of age or older) that evaluate each of the four broad domains (cognitive, motor, sensory, and affect) essential to neurobehavioral assessment. Children were classified as exposed or unexposed using urinary p-nitrophenol (PNP) levels and environmental wipe samples for MP. Exposure was defined as a urinary PNP level of greater than or equal to 100 ppb for the child or any other individual living in the household. Environmental wipe sample levels of greater than or equal to 150 g MP/100 cm2 and greater than or equal to 132.9 g MP/100 cm2 were used to define MP exposure for children living in Mississippi and Ohio, respectively. The PENTB was first administered in summer 1999 (year 1). The PENTB was readministered in summer 2000 (year 2) to children who participated in year 1 of the study. A description of the methods used in the study are presented. Results of data analyses for both years of the study will be presented in a separate publication.

During the last several years, illegal commercial application of methyl parathion (MP) in domestic settings in several U.S. Southeastern and Midwestern States has affected largely inner-city residents. As part of a multiagency response involving the U.S. Environmental Protection Agency (U.S. EPA), the Agency for Toxic Substances and Disease Registry (ATSDR), and state and local health departments, our laboratory developed a rapid, high-throughput, selective method for quantifying p-nitrophenol (PNP), a biomarker of MP exposure, using isotope dilution high-performance liquid chromatography-tandem mass spectrometry. We measured PNP in approximately 16,000 samples collected from residents of seven different states. Using this method, we were able to receive sample batches from each state; prepare, analyze, and quantify the samples for PNP; verify the results; and report the data to the health departments and ATSDR in about 48 hr. These data indicate that many residents had urinary PNP concentrations well in excess of those of the general U.S. population. In fact, their urinary PNP concentrations were more consistent with those seen in occupational settings or in poisoning cases. Although these data, when coupled with other MP metabolite data, suggest that many residents with the highest concentrations of urinary PNP had significant exposure to MP, they do not unequivocally rule out exposure to PNP resulting from environmental degradation of MP. Even with their limitations, these data were used with the assumption that all PNP was derived from MP exposure, which enabled the U.S. EPA and ATSDR to develop a comprehensive, biologically driven response that was protective of human health, especially susceptible populations, and included clinical evaluations, outreach activities, community education, integrated pest management, and decontamination of homes.

The Illinois Department of Public Health participated in the Chicago, Illinois, area methyl parathion (MP) response with several other federal, state, and local government agencies beginning in April 1997. This response was initiated on evidence that hundreds of homes in the Chicago area were illegally treated for cockroaches with MP over a period of several years. Through applicator receipt books and information reported by property owners and tenants, 968 homes were identified as having been treated with MP. Upon implementation of a response plan developed by the Methyl Parathion Health Sciences Steering Committee, environmental sampling and urine monitoring were provided for eligible households. Environmental sampling was conducted in 903 homes, with MP detected above levels of concern in 596 residences. Residents of these homes were offered urine sampling to determine the extent of exposure to MP. Urine samples were collected and analyzed for p-nitrophenol in 1,913 individuals. Implementation of the protocol resulted in 550 residents being relocated during the remediation of 100 households.

Methyl parathion (MP) is an organophosphate pesticide illegally applied to the interiors of many hundreds of homes throughout the United States by unlicensed pesticide applicators. Public health authorities developed a protocol for investigating contaminated homes and classifying their need for public health interventions. This protocol included environmental screening for MP contamination and 1-day biomonitoring (a.m. and p.m. spot urine samples) of household members for p-nitrophenol (PNP), a metabolite of MP. The variability of urinary PNP excretion under these exposure conditions was unknown. We collected a.m. and p.m. spot urine samples for 7 consecutive days from 75 individuals, who were members of 20 MP-contaminated households in the greater Chicago, Illinois, area, and analyzed them for PNP. We also assessed the ability of the 1-day sampling protocol to correctly classify exposed individuals and households according to their need for public health interventions, assuming that 1 week of sampling (14 urinary PNPs) represented their true exposure condition. The coefficient of variation of log urinary PNPs for individuals over the course of 7 days of a.m. and p.m. sampling averaged about 15%. Adjusting for urinary excretion of creatinine improved reproducibility of urinary PNPs among children but not among adults. The 1-day protocol correctly classified true risk category in 92% of individuals and 85% of households. The data contained in this study can be used to refine what is already a reasonable and effective approach to identifying MP-exposed households and determining the appropriate public health intervention.

In 1994 officials from the Ohio Department of Health reported that some residents of Lorain County, Ohio, possibly had been exposed to methyl parathion (MP), a highly toxic restricted-use pesticide. The U.S. Centers for Disease Control and Prevention (CDC) assisted in the investigation by providing epidemiologic and laboratory support to the state and local health departments. Although the initial investigation found MP inside the homes, it was unclear if the residents were exposed. CDC used a new biological monitoring method to measure urinary p-nitrophenol (PNP), the metabolite of MP. This biological monitoring measures the internal dose from exposure to toxic chemicals from all routes. Laboratory analyses demonstrated that the urine of residents contained moderate to high levels of PNP, with median, mean, and highest reported concentrations of 28, 240, and 4,800 g/L, respectively, thus confirming exposure of the residents. Almost 80% of the residents had urinary PNP concentrations above the 95th percentile of the reference range concentrations. This information, combined with other analytical results of air and wipe tests, guided public health officials' decisions about the potential risk in each household. In this article we illustrate the laboratory's role in providing information to assist in making these public health decisions. Furthermore, it illustrates how a multidisciplinary team from various governmental agencies worked together to protect the public's health.

Adult pre-spawning fish Labeo rohita were sublethally (1/5th 96h LC50) exposed to mercuric chloride and metacid-50 (methyl parathion). Accumulation of mercury and methyl parathion was studied and it was found that pre-spawning ovary appears as a potent organ for deposition of both the pollutants. RNA/DNA ratio of the control and treated fish were studied. It was found that the signifcant decrease in RNA/DNA ratio occurs after 9 and 30 days of exposure for mercury and 30 days for methyl parathion. Fluorescence microscopic studies by acridine orange staining method were also performed to show how much it is related to biochemical alterations. In some cases loss of metachromasia is correlated with the fall in RNA/DNA ratio. Some other abnormalities like fall in stage II: stage I oocyte ratio and necrosis was also observed.

The role of cytochrome P450 (CYP) and the CYP isoform involved in the activation of the widely used pesticide methyl-parathion (MePA) were investigated in rat brain extracts by measuring the effect of different CYP inhibitors on acetylcholinesterase (AChE) inhibition by MePA. Brain extracts provide a useful tool to study the activation mechanisms of organophosphorus compounds (OP) since they contain both the activating enzyme(s) and the molecular target for OP toxicity. As expected, in incubations of rat brain extract supplemented with NADPH, AChE activity was non-competitively inhibited by the presence of MePA, indicating that MePA was activated to its reactive metabolite methyl-paraoxon (MePO). Indeed, Vmax(app) decreased from 13.4 to 8.7 micromol thionitrobenzoic acid (TNB)/min per mg protein. MePA activation by rat brain extracts, as measured by the AChE inhibition produced by the presence of the pesticide in the incubation, was fully prevented by previously bubbling the incubation mix with CO, by the presence of monoclonal anti-rat CYP2B1/2B2 antibodies and by the addition of phenobarbital (PB), a CYP2B substrate. Interestingly, MePA showed a greater affinity for CYP2B than PB. CYP1A1 antibodies showed no effect on MePA activation. The presence of cytochrome P450 2B (CYP2B) in the rat brain extracts was confirmed by immunoblotting. These results demonstrate indisputably the responsibility of CYP2B in MePA activation in the rat brain in vitro, suggesting that metabolic activation of OP compounds in situ might be crucial for their organ specific toxicity to the central nervous system also in vivo.

Acetylcholinesterase activity was determined for midge larvae (Chironomus tentans) exposed to either organophosphorus insecticides (OPs) alone or OP insecticides in binary combination with atrazine (200 microg/l). Although atrazine by itself did not reduce the level of acetylcholinesterase activity, atrazine in combination with chlorpyrifos significantly decreased acetylcholinesterase activity as compared to chlorpyrifos only treatments. Although similar trends existed for malathion and methyl parathion, differences were not statistically significant. These results match previously published toxicity data where atrazine, although not acutely toxic even at much higher levels, decreased EC50 values for chlorpyrifos by a magnitude of 4, decreased methyl parathion values by a magnitude of 2, and did not decrease values for malathion.

The paper gives a sanitary characterization of working conditions in closed soil vegetable growing, a branch of agriculture. These conditions are one of the factors predisposing to occupational disease in agricultural workers. Studies in this area may evaluate the risk of occupational diseases.

A study conducted by the Agency for Toxic Substances and Disease Registry (ATSDR), a US public health agency, evaluated ATSDR's risk communication process, specifically the roles and responsibilities, planning, implementation, and coordination of activities in response to illegal indoor spraying of methyl parathion, a hazardous pesticide, in Pascagoula, MS. Interviews of staff members involved in the intervention were conducted and an analysis revealed strengths and areas in need of improvement in the design and implementation of risk communication strategies. Key recommendations included developing a clear strategy for planning and conducting communication activities; determining staff roles and responsibilities for coordination; and developing clear and consistent health messages, a dissemination strategy, and training in the delivery and evaluation of messages, effects, and outcomes.

Human-induced disasters have long been considered responsible for a wide array of physiological, psychological, and economic distress. This study examined depressive symptoms among victims of south Mississippi's methyl parathion disaster. Results indicated that irrespective of the level of methyl parathion contamination in respondents' dwellings, more than half the victims interviewed reported depressive symptoms at levels suggesting probable clinical depression. Those at greatest risk of depressive symptoms were people who had been exposed to the neurotoxin for the longest period of time, among whom there was an overrepresentation of women and African Americans. Despite high statistical levels of depression, few victims used mental health services. Implications for social work's response to human-induced disasters are provided.

Background: A study of the prevalence of sperm aneuploidy among pesticide factory workers was conducted in Anhui, China., Methods: We recruited 75 men: 32 subjects from a large pesticide-manufacturing plant and 43 subjects from a nearby textile factory free of pesticide exposure. Each subject met the following criteria: age of 20-40 years; continuous work in the plant for 3 months prior to the study, no congenital anomalies or acquired disease of the external genitalia and no history of recent febrile illness or mumps. Within one hour after collection from each subject, semen was evaluated in terms of several parameters and smear slides were prepared., Results: Exposure assessment revealed that workers in the pesticide plant were exposed to ethyl parathion or methamidophos, each of which is a potent organophosphate pesticide, at a median level of 0.02 mg/m3 (8-hour time weighted average as measured by personal pump) while workers in the control plant had no such occupational exposure. Twenty-nine semen slides (13 from the exposed group and 16 from the unexposed group) were randomly chosen for aneuploidy scoring by the three-color fluorescence in situ hybridization (FISH) method with scorers being unaware of exposure status. Median semen parameters were as follows for exposed (and unexposed) men: abstinence period, 3 days (4 days); sperm concentration, 52.8x10(6)/ml (53.1x10(6)/ml); proportion of sperm with normal motility, 50.5% (61.3%); and proportion of sperm with normal morphology, 59% (61.5%). The specific chromosome abnormalities of interest were disomy for chromosome 18 and the three different types of sex chromosome disomy (i.e. XX, XY, YY disomy). The crude proportion of all aneuploidy combined was 0.30% and 0.19% for sperm from exposed and unexposed men, respectively. Poisson regression with overdispersion adjustment yielded significantly different crude risks of aneuploidy - 3.03 and 1.94 per 1,000 sperm from exposed and unexposed men, respectively - giving a rate ratio of 1.56 (95% CI, 1.06-2.31). The regression coefficients remained statistically significant after adjustment for inter-technician variability giving a rate ratio of 1.51 (95% CI, 1. 04-2.20)., Conclusions: We conclude that occupational exposure to organophosphate pesticides moderately increases the prevalence of sperm aneuploidy., (Copyright 1999 Wiley-Liss, Inc.)

Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone levels, as well as urinary levels of FSH, LH, and E1C, a metabolite of testosterone, were measured to investigate the adverse reproductive effects of organophosphate pesticides among Chinese factory workers who were occupationally exposed to ethylparathion and methamidophos. Thirty-four exposed workers were randomly chosen and recruited from a large pesticide factory, and 44 unexposed workers were selected from a nearby textile factory. A quantitative pesticide exposure assessment was performed among a subset of the exposed and unexposed workers. Information on potential confounders was collected in an interview. A single blood sample was collected at the end of a work shift, when each subject also donated a semen sample. Three first-voided urine samples were collected from each worker on 3 consecutive days. Urinary p-nitrophenol level at 1 hour after the work shift correlated with serum (r = 0.71, P < 0.01) and urinary (r = 0.51, P = 0.04) FSH levels. Stratifying by the subjects' exposure status, we found a significant negative correlation among the exposed group between urinary FSH level and sperm count (r = -0.61, P < 0.01) and between urinary FSH level and sperm concentration (r = -0.53, P = 0.03). Pesticide exposure alone was significantly associated with serum LH level (beta [coefficient of exposure effect] = 0.79; 95% confidence interval [CI] = 0.42, 1.16) but not with serum FSH or testosterone or with any urinary hormone levels. With adjustment for age, rotating shift work, current cigarette smoking, and current alcohol consumption, exposure significantly increased the serum LH level by 1.1 mIU/mL (95% CI = 0.34, 1.82). Meanwhile, the serum FSH level was slightly elevated (beta [coefficient of exposure effect] = 1.38; 95% CI = -0.09, 2.85) and the serum testosterone level was decreased (beta = -55.13; 95% CI = -147.24, 37) with increased pesticide exposure. Age and rotating shift work appeared to act as confounders. We conclude that organophosphate pesticides have a small effect on male reproductive hormones, suggestive of a secondary hormonal disturbance after testicular damage.

Franz diffusion experiments with human skin combined with work-clothing fabric have shown that skin exposure to pesticides is reduced by the presence of traditional nonbarrier textiles. This study was undertaken to obtain further information about the reduction in exposure using traditional work-clothing fabrics that had chemical finishing to increase the sorption properties. The effects of a renewable starch finish and chemical modification by carboxymethylation on cotton fabrics on the pesticide (methyl parathion) retention, transfer, and decontamination by laundering were investigated. Two weights of work clothing fabrics made of 100% cotton were used, one appropriate for shirts and the other for pants. The amount of pesticide observed on human skin was reduced by the presence of clothing fabric. Carboxymethylation of the shirt fabric reduced the amount of pesticide observed on the human skin. This treatment also resulted in less pesticide being transferred to a second fabric layer within a clothing system. No pesticide penetrated to the second fabric layer when the heavier pant fabric was used as the outer layer. The lighter weight shirt fabric did not retain as much pesticide as the pant fabric. The pesticide retained on the shirt fabric was increased by the application of a renewable starch finish and by carboxymethylation; both of these finishes were found to be effective in enhancing the decontamination of cotton fabrics by laundering.

The effect of methyl parathion (MP) on developing chick embryos was investigated. The embryos were exposed at different stages of development to various doses of MP via the yolk sac route. This resulted in retarded growth which included reduced body weight and reduced body length and length of leg bones. Other teratogenic signs observed were short neck, muscular hypoplasia of legs, abdominal hernias and haemorrhagic spots in brain and upper body. These findings suggest that MP was a teratogen when injected into the yolk sacs of developing embryos.

Exposure to a sublethal concentration of methyl parathion (MEP) reduced the activity of cytoplasmic malate dehydrogenase, mitochondrial malate dehydrogenase, and lactate dehydrogenase by 30 to 49% in the liver and the skeletal muscle of the freshwater catfish. Clarias batrachus, after 7 days. The activities then began to recover and reached the control levels on the 28th day of MEP exposure. A complete recovery occurred on the 7th day when MEP was withdrawn from the medium after an exposure for 1 week. The withdrawal-dependent recovery in the activities was inhibited partially or completely by actinomycin D and cycloheximide, suggesting de novo synthesis of the enzymes during the recovery period. A conjoint treatment of MEP and triiodothyronine (T3) restored the activities to control levels, indicating T3 protection against the pesticide toxicity. SDS-PAGE of the cytoplasmic fraction of the liver showed some noticeable changes in the protein pattern after an exposure to MEP. Ultrastructural studies on MEP-treated liver cells showed disappearance of the glycogen granules and appearance of numerous smooth endoplasmic reticulum, lysosomal dense bodies, and swollen mitochondria. These changes in the liver are an indication of hepatic toxicity leading toward necrosis.

When compared with non-exposed controls, a group of pesticide plant workers chronically exposed to methyl-parathion did not show an increased frequency of chromosome aberrations in lymphocyte cultures. Although methyl-parathion increased chromosome aberrations in cases of intoxication, a chronic exposure to small doses in the work place did not seem to produce the same effect.

The AA describe a case of retinal degeneration (cones and rods degeneration) which has arisen in a subject exposed to organophosphorous pesticides. The AA. discuss about the evidences of specialistic tests and point out the necessity of a particular attention to the sight apparatus in field of toxic exposures.

In an epidemiological study in the Neubrandenburg district among 316 long-term exposed pesticide workers the incidence of tumors was investigated. There were 30 cases of tumors, of which 11 were lung cancers. The incidence of lung cancers was in contrast to age-specific population twenty times higher. The average exposure against pesticides amounted to 14.1 +/- 4.7 (6-23) years, the latency period between exposition start and tumor manifestation to 17.9 +/- 6.0 (6-23) years. The exposure occurred mainly to the following agents: herbicides, such as derivatives of phenoxyacetic acid (2,4 D and MCPA); insecticides, such as chlorinated hydrocarbons (DDT, HCH and Toxaphen), organic phosphorus compounds (Parathion) and organic nitro derivatives (DNOC) as well as fungicides, such as copper containing and organic synthetic agents. Between 1950 and 1956 some pesticide workers were also exposed to arsenic containing agents. As the workers were exposed to various chemical compounds simultaneously or alternatively, no carcinogenic effect can be determined by specific individual pesticides. The investigations are discussed in detail on the today knowledge about cancer hazards associated with exposure to pesticides, and respective conclusions are drawn for preventive measures.