Effects of pesticide exposure on the human immune system.

Epidemiological evidence from Western countries indicates that the prevalence of diseases associated with alterations in the immune response, such as asthma, certain autoimmune diseases and cancer, are increasing to such an extent that it cannot be attributed to improved diagnostics alone. There is some concern that this trend could be, at least, partially attributable to new or modified patterns of exposures to chemicals, including pesticides. The purpose of this article is to review the evidence on pesticide immunotoxicity in humans. Overall, the available data are inadequate to draw firm conclusions on the immunotoxic risk associated with pesticide exposure. The available studies on the effects of pesticides on the human immune system have several limitations, including limited data on exposure levels, heterogeneity of the applied methods, and difficulties in assessing the prognostic significance of observed slight changes and in the interpretation of the reported findings. Further studies are needed and preferably as prospective studies, comparing pre- and post-exposure data in the same group of subjects and including an appropriate non-exposed control group. More knowledge is required regarding the prognostic significance of the small changes observed.

Biological monitoring and questionnaire for assessing exposure to ethylenebisdithiocarbamates in a multicenter European field study.

This study deals with pesticide exposure profile in some European countries with a specific focus on ethylenebisdithiocarbamates (EBDC). In all, 55 Bulgarian greenhouse workers, 51 Finnish potato farmers, 48 Italian vineyard workers, 42 Dutch floriculture farmers, and 52 Bulgarian zineb producers entered the study. Each group was matched with a group of not occupationally exposed subjects. Exposure data were gained through self-administered questionnaires and measuring ethylenethiourea (ETU) in two spot urine samples collected, respectively, before the beginning of seasonal exposure (T0), and after 30 days, at the end of the exposure period (T30). Controls underwent a similar protocol. Study agriculture workers were involved in mixing and loading pesticides, application of pesticide mixture with mechanical or manual equipments, re-entry activities, and cleaning equipments. Chemical workers were involved in synthesis, quality controls, and packing activities. The number of pesticides to whom these subjects were exposed varied from one (zineb production) to eight (potato farmers). The use of personal protective devices was variegate and regarded both aerial and dermal penetration routes. EBDC exposure, assessed by T30 urinary ETU, was found to follow the order: greenhouse workers, zineb producers, vineyard workers, potato farmers, floriculture farmers with median levels of 49.6, 23.0, 11.8, 7.5, and 0.9 microg/g creatinine; the last group having ETU at the same level of controls (approximately 0.5 microg/g creatinine). Among agriculture workers, pesticide application, especially using manual equipment, seems to be the major determinant in explaining internal dose. Although the analysis of self-administered questionnaires evidenced difficulties especially related to lack and/or poor quality of reported data, biological monitoring confirms to be a powerful tool in assessing pesticide exposure.

Immune effects and exposure to ethylenebisdithiocarbamate pesticides in re-entry workers in the Netherlands.

Ethylenebisdithiocarbamates are widely used as fungicides in agriculture. Although EBDC's have a low acute toxicity, they are suspected to have immune effects at low doses. However, little human studies on these effects have been published. In the Netherlands, a study was conducted among pesticide exposed workers aimed at evaluating the short-term and long-term immune effects of exposure and the relation between ethylenebisdithiocarbamate and immune effects. Forty-one re-entry workers and 40 nonexposed controls were medically examined; furthermore, immune parameters were determined in blood, and all participants filled in a questionnaire regarding exposure and outcome parameters. The level of ethylenethiourea in urine was determined as indicator of exposure. No relevant adverse immune effects were found in the pesticide exposed workers compared with the nonexposed controls. Also no exposure response relationship between immune effects and ethylenebisdithiocarbamate in urine was found. This finding might be due to very low exposure levels of the re-entry work but might also be due to a lack of immunotoxicity of ethylenebisdithiocarbamate at normal exposure levels.

Toxicological evaluation of the immune function of pesticide workers, a European wide assessment.

In this study, the prolonged low-dose exposure of mixtures of pesticides has been examined on hematological parameters and components of the immune defense in occupationally exposed humans. This investigation was carried out in five field studies in: the Netherlands (flower bulb growers, mainly re-entry workers), Italy (vineyard workers), Finland (potato farmers), and Bulgaria (workers from a zineb factory and greenhouse workers). Immunotoxicity was studied by measuring hematological parameters, complement, immunoglobulins, lymphocyte subpopulations, natural killer cells, autoimmunity, and antibody responses to hepatitis B vaccination. The total study population consisted of 248 pesticide-exposed and 231 non-occupationally exposed workers. As a surrogate measure of pesticide exposure the urinary excretion of ethylenethiourea (ETU), the main metabolite ethylenebisdithiocarbamates was measured. A significantly higher level of ETU in occupationally exposed subjects compared with controls (2.7 +/- 8.1 microg/g vs 0.5 +/- 3.7 microg/g creatinine) was found. Statistically significant differences, albeit very low, were found for complement C3 and C4 and the immunoglobulin classes IgG4 and IgA. For complement and IgG4, the levels were slightly increased and the level of IgA was decreased. In the lymphocyte populations, the CD8 subpopulation was increased. No effects were found on autoimmune antibodies and antibody response to hepatitis vaccination. In conclusion, pesticide exposure under various work place conditions in Europe was associated only with some subtle effects on the immune system, which may suggest that occupational exposure to pesticides does not influence the immunologic system in a clinically significant fashion, and does not pose a significant health risk to the exposed subjects.

Occupational exposure to ethylenebisdithiocarbamates in agriculture and allergy: results from the EUROPIT field study.

This epidemiological study was carried out to evaluate the possible association between occupational exposure to ethylenebisdithiocarbamates (EDBC) and allergy. The study was conducted in four countries in the European Union: The Netherlands, Finland, Italy and Bulgaria. A total of 248 workers exposed to EDBC and 231 non-occupationally exposed subjects entered the study. Exposure to EDBC was measured as urinary ethylenethiourea (ETU) in urinary samples collected at baseline and after 30 days of exposure. Several effect parameters were evaluated including questionnaire data on allergy, Phadiatop, a general allergy test, and specific IgE parameters. These data were also collected at baseline and after 30 days of exposure. Cross-sectional as well as longitudinal comparisons were made, adjusted for potential confounding factors. No association was found between exposure status, EDBC levels and allergic contact dermatitis, allergic rhinitis, food allergy or atopy as measured by the Phadiatop. The prevalence of skin irritation was elevated in the Dutch field study only and is more likely a result of plant contact rather than EDBC exposure. Occupational exposure to sunlight was noted to have a protective effect on atopy in terms of IgE positivity. We conclude that the EDBC exposure levels experienced in our field study are not associated with increased prevalence of allergic symptoms or allergy.

Asthmatic symptoms after exposure to ethylenebisdithiocarbamates and other pesticides in the Europit field studies.

We conducted a multicenter prospective study to assess the effects of occupational exposure to ethylenebisdithiocarbamate fungicides and/or other pesticides on self-reported asthma and asthmatic symptoms. This multicenter study was conducted among 248 workers exposed to pesticides and 231 non-exposed workers from five field studies. The five field studies were carried out in The Netherlands, Italy, Finland, and two studies in Bulgaria. Subjects constituting this cohort completed a self-administered questionnaire at baseline (before the start of exposure). Ethylenethiourea in urine was determined to assess exposure to ethylenebisdithiocarbamates. In multivariate analyses adjusted for all potential confounders (age, education, residence, smoking, gender, and field study), we found inverse associations, all not statistically significant, between occupational exposure to pesticides and asthma diagnosis (OR 0.41; 95% CI 0.15-1.11), complains of chest tightness (OR 0.60; 95% CI 0.36-1.02), wheeze (OR 0.56; 95% CI 0.32-0.98), asthma attack (OR 0.52; 95% CI 0.12-2.25), and asthma medication (OR 0.79; 95% CI 0.25-2.53). Furthermore, we reported null associations for multivariate analysis using ethylenethiourea as determinant for exposure. Although exposure to pesticides remains a potential health risk, our results do not suggest an association between exposure to ethylenebisdithiocarbamates and/or other pesticides used in our study on asthma and asthmatic symptoms.

Single day treatment--a feasible tool in revealing not dependent on maternal toxicity teratogenic potential.

The aim of this study is to explore the applicability of single day treatment for separation of development effects as an intrinsic property from those related to maternal toxicity. The fungicides paclobutrazole and benomyl were administered to pregnant rats on days 6 to 15 and on 7, 9, 11 and 13 day of gestation. After a single treatment higher percentage of fetuses were with external and visceral anomalies.

Toxicological evaluation of agromet (Metalaxyl) preparation.

A complex toxicological study was carried out in relation to the hygienic standardization of the fungicide preparation Ridomil, whose forthcoming production in this country will be under the name Metalaxyl. The study was performed on sexually mature white rats of both sexes, at oral, dermal and inhalation exposure, acute, subacute and chronic experiments, according to the Bulgarian State Standard. Besides the routine toxicological studies were carried also studies for establishing the long-term effects of the preparation (gonadotropic, embryotoxic and teratogenic, cardiovascular). The results from the study permitted the Agromet preparation to be put in III class--moderately toxic according to limiting index LD50 oral. On the basis of data from the authors study on the general toxicity and long-term effects of Metalaxyl a temporary MAC 4 mg/m3 was proposed.

Behavioral teratology--results achieved and perspectives of development.

The objective of behavioral teratology is to throw light on the consequences of prenatal effect of the agent on varying aspects of the functional state of the nervous system. In the present paper, the author proposes Carbendazim as a model of Type 1 behavioral teratogen (agent provoking morphological anomalies in the CNS). On this model, the author studied the sensitivity of a group of primary screening tests proposed in the literature, introducing semiquantitative and quantitative criteria for determining the level of response. The study of the postural reflex and behaviour in the open field were found to be the most sensitive. The latter also provides the possibility of demonstrating some qualitative deviations in behaviour, such as the "jumping" gait.

[Experimental study of the teratogenicity and embryotoxicity of endodan]. / Eksperimentalno prouchvane na endodan za teratogennost i embriotoksichnost.

An experiment was carried out on albino rats for the assessment of the effect, during gestation, of the fungicide endodan (ethylene - thiuram monosulphide) on the intrauterine and postnatal development of the progeny. A low teratogenic and embryotoxic activity was established after a single treatment with I/2 LD50 on 13 th gestation day. The preparation is with a pronounced cumulative effect in a daily administration of 1/5, 1/10 and 1/20 LD50, manifested by clinical symptomatics and lethality of a part of the pregnant animals. Via tests for the assessment of the behaviour, deviations in the functional state of the nervous system of the progeny were established, with no changes in the integral indices - viability and body weight gain during the postnatal period.

[Current methodologic approaches to the study of various delayed effects of pesticides]. / Suvremenni metodologichni podkhodi pri izuchavane niakoi otdalecheni efekti na pestitsidite.

Studies on the possibilities of origination of remote sequelae (embryotoxic and teratogenic, gonadotropic, mutagenic, carcinogenic, alterations in cardiovascular system, etc) under the effect of the wide application of pesticides in the practice is one of the most important aspects of the present-day toxicology. Numerous of our studies in that field are directed to the pesticides, to fungicides in particular, the greater part of them being with mechanisms of biological activity, triggering changes in DNA synthesis and disturbances in cellular respiration. The results from our experimental studies are presented in the communication, with an aspect of alterations in the gonads, embryotoxicity and teratogenicity, of representatives of various groups of chemical preparations for plant protection. The eventual use of those data in the prognosis of potential risk for humans is discussed. Model conditions are proposed for a more thorough assessment and more accurate determination of threshold levels of effect with a view to their utilization in hygienic standardization.

[Assessment of the potential risk for progeny in work with endodan (experimental studies)]. / Otsenka na potentsialniia risk za pokolenieto pri rabota s endodan (eksperimentalni prouchvaniia).

An experimental assessment was made on endodan (ETM) effect, dithiocarbamate preparation, on the reproductive function of the parent generation albino rats, perorally intoxicated (by a sound) with doses 1/10 and 1/100 LD50, daily in the course of 6 months (LD50 = 380 mg/kg). The postnatal development of the three successive generations (F1, F2, F3) was studied. For that purpose, a complex of integral toxicological methods was used: weight, neurobehavioural activity, nortality (by 1st, 5th, 21st day), with the calculation of the indices of survival and lactation, and fertility with calculation of the indices of fertility and gestation and biochemical and clinical laboratory methods for the assessment of the functional state of liver, brain and testes. The embryotoxic and teratogenic activity of endodan was assessed with a single (175 and 70 mg/kg, administered on the 9th, 11th and 13th day) and repeated (daily 70 and 35 mg/kg) peroral administration in the course of gestation. The routine teratological methods were used: number of yellow bodies, number of implantation with resorption autolysis and living fetuses, structural anomalies; assessment of the state of the internal organs (Wilson) and the skeletal system (Dowson). A test for dominant lethality was used for the evaluation of the mutagenic effect, under the conditions of subacute experiment. As a result a light gonadotropic effect was found (single deviations in the early postnatal development of the progeny, light teratogenic and mutagenic activity). The authors drew conclusions concerning the relatively higher perspectives of that dithiocarbamate preparation for the practice as regards the potential risk of the population. Consideration given to its higher dermal toxicity and cumulation effect, confirmed with the previous investigations and the total toxicological characteristic of dithiocarbamate, they stressed upon the necessity of the strictest observation of the hygienic standards and rules of safe work.

Study on the long-term effects of some pesticides.

The hygienic significance of the studies on pesticides from the aspect of their "long-term" effects upon the individual and the generations are emphasized. The basic methods and approaches used in the Laboratory of long-term effects with chemical etiology at the IHOH, Sofia, are discussed, namely for detecting the changes in gonads, reproduction and generation, embryotoxic and teratogenic effects, and changes in cardiovascular system. The results are discussed, namely: fundasol--the effect on gonads, generations, embryotoxic and teratogenic effects, changes in the cardiovascular system; endodan--changes in gonads, reproduction, embryotoxicity; basfungin--embryotoxic and teratogenic effects. All of these studies were performed for the purpose of threshold levels, establishment hygienic standardisation and prognosis of the potential risk for human.

Experimental studies on the chronic toxic effects of vinyl chloride in rats.

Male rats were exposed to vinyl chloride at the concentrations of 50, 500, and 20 000 ppm, 5 hours daily, 5 days a week for 10 months. Morphological lesions in the liver and the testes detected by light and electron microscope and depression in body weight increase intensified with the duration of exposure. Increased relative weights of some organs and slight hematological and biochemical changes in blood during the course of the experiment were also observed. Some toxic effects including morphological liver injuries arose at the smallest exposure level, i. e., 50 ppm. Assuming 50 ppm as the threshold concentration for rats, the 5 ppm level has been estimated as the safe exposure limit in industry in relation to systemic effects of vinyl chloride.

[Potential teratogenic action of the mycelium of the higher fungus, Polyporellus squamosus]. / Prouchvane ne vuzmozhnoto teratogenno deistvie na mitsel ot visshata guba Polyporellus squamosus.

The influence on the embryonic development of food with only source of protein derived from the mycelium of the higher fungus Polyporellus squamosus, was studied in a group of 90 pregnant rats. Animals fed caseine and standard food pressed into briquettes as source of protein served as controls. On the 17-th and 18-th gestation day 8 animals were examined and the number of of lutein bodies and fetuses was checked up. Anomalies were serched in the fetuses, by use of the method of Dawson and Wilson. The progeny of rats treated during gestation was examined on the 21-st day of life, by using a number of blood, integral and biochemical parameters (GOT, GPT, AP, SDH, catalase, sulfhydryl groups, soluble, protein). Proceeding from the results obtained, the authors rule out any teratogenic and embryotoxic activity of the mycelium of Polyporellus squamosus, under the aforegoing experimental conditions.

[Embryotoxic and teratogenic action of some pesticides]. / Embriotoksichno i teratogenno deistvie na niakoi pestitsidi

The authors carried out experiments on white rats in order to evaluate embriotoxic and teratogenic effect of pesticides: cyneb, mneb, cypromate, basfungine, remrod, dipterex and bromex. The preparations were administered oraly as followed: 1) singly in the course of whole pregnancy in a dose of 1/2 LD50 and lower doses till finding single nonacting dose and 21 in the course of the whole pregnancy in doses rangling from the determined single threshold dose till finding minimal acting dose during multiple application and nonacting teratogenic dose under the same conditions. The authors examined the changes in some liver enzymic systems of the mother and fetus. It was established that there was raised actitity of LDH, A1Ph, AcPh, glucose -6-phosphat-dehydrogenase and HEA with degree differences in both examined categories - the mother and fetus. Single treatment of pregnant rats during the period of organogenesis induced anomalies in the development of the nervous system; of the skeletal system - facial cranium, extremities, tail as well as functional and biochemical changes. The authors determined teratogenically nonacting doses for single application: for cyneb - 1000 mg/kg; for maneb - 50 mg/kg and for cypronat - 250 mg/kg.