Relationship between chlordane and its metabolites in blood of pest control operators and spraying conditions

Biological Monitoring of Pesticide Exposure: a review. Introduction

Pesticides are used worldwide in agriculture, industry, public health and for domestic applications: as a consequence, a great part of the population may be exposed to these compounds. In spite of this extensive use, knowledge on the health risks associated with prolonged exposure is rather poor, and major uncertainties still exist. Epidemiological observations in man have so far produced little conclusive information, mainly because of weaknesses in exposure assessment. Therefore, information on the type and levels of exposure is fundamental in order to better understand and characterize risk to human health. Exposure assessment can be carried out via measurement of environmental concentrations, as well as via determination of the chemical or its metabolites in body tissues (biological monitoring). Besides indices of internal dose, biological monitoring also includes measurements of early effects attributable to interaction between the chemical agent and the human body. Biological monitoring has the advantage, over environmental monitoring, of determining the dose actually absorbed via any possible route: differences in absorption can be taken into account. whether they are due to biological variability or to use of protective equipment. When, in some cases, a combination of occupational and non-occupational exposure occurs, this also can be taken into consideration by biological monitoring. Few reference documents have been published on biological monitoring of pesticides. For this reason, the Office of Occupational Health of the World Health Organization gave ICPS a mandate to prepare a monograph specifically addressed to reviewing methods for biological monitoring of pesticide exposure. This review is based on more than 300 studies published over the period 1980-1999. For the most representative chemical classes, the available biological exposure indices are reported. Both indices of internal dose and. when available, of early effects are discussed. The reported tests were used to monitor exposure of pesticide applicators in agriculture and public health, manufacturing and formulating workers. subjects poisoned after accidental exposure or attempted suicide, volunteers involved in pharmacokinetic studies, as well as sub-groups of the general population exposed to environmentally persistent pesticides. Single chapters deal with organophosphorus insecticides, carbamate pesticides, dithiocarbamates, phenoxyacids, quaternary ammonium compounds. coumarin rodenticides, synthetic pyrethroids, organochlorine pesticides, chlorotriazines, and pentachlorophenol.

[Delayed effects of organochlorine pesticides in man]

Available information on organochlorines and the chronic effects of exposure to them are set out. Organochlorinated compounds are the most persistent pesticides and can be found in all ecosystems. Although they are generally efficient in pest control, they are also a potent environment pollutant and can provoke health problems in man. The evidences of the carcinogenic potential of organochlorines are controversial and insufficient, but they have been related to an increase in the incidence of some kinds of tumors, such as leukemia and solid tumors. Reproductive effects, due to anti-androgenic and estrogenic action, on embryonic virilization, the incidence of abortion and the frequency of prematurity, have also been observed. The accumulation of the organochlorines in the adipous tissue is positively correlated to the increase in aging and could be implicated in the development of aging diseases, such as Parkinson's disease. The effects of pesticides on human health have not yet been completely elucidated. Genotoxicity is one of the most serious of the possible harmful effects caused by these compounds and calls for special attention in view of the irreversible nature of the process and to the long latency associated with its manifestation.

Biomarkers of human exposure to pesticides

For centuries, several hundred pesticides have been used to control insects. These pesticides differ greatly in their mode of action, uptake by the body, metabolism, elimination from the body, and toxicity to humans. Potential exposure from the environment can be estimated by environmental monitoring. Actual exposure (uptake) is measured by the biological monitoring of human tissues and body fluids. Biomarkers are used to detect the effects of pesticides before adverse clinical health effects occur. Pesticides and their metabolites are measured in biological samples, serum, fat, urine, blood, or breast milk by the usual analytical techniques. Biochemical responses to environmental chemicals provide a measure of toxic effect. A widely used biochemical biomarker, cholinesterase depression, measures exposure to organophosphorus insecticides. Techniques that measure DNA damage (e.g., detection of DNA adducts) provide a powerful tool in measuring environmental effects. Adducts to hemoglobin have been detected with several pesticides. Determination of chromosomal aberration rates in cultured lymphocytes is an established method of monitoring populations occupationally or environmentally exposed to known or suspected mutagenic-carcinogenic agents. There are several studies on the cytogenetic effects of work with pesticide formulations. The majority of these studies report increases in the frequency of chromosomal aberrations and/or sister chromatid exchanges among the exposed workers. Biomarkers will have a major impact on the study of environmental risk factors. The basic aim of scientists exploring these issues is to determine the nature and consequences of genetic change or variation, with the ultimate purpose of predicting or preventing disease.

Biological monitoring of occupational pesticides exposure

Two kinds of measurement: (1) enzyme activities in blood, and (2) unchanged pesticides and their metabolites in urine or blood have been used in biological monitoring for assessing exposure to pesticides. The assays of acetylcholinesterase (AChE) activity in whole blood and erythrocytes are mainly applied to estimate inhibition by organophosphates (OPs) and carbamates. A level at 70% of an individual's baseline or of a mean population AChE activity has been recommended as a reference value for exposure control. The measurement of lymphocyte "neuropathy target esterase (NTE)" activity in subjects handling axonopathic OPs is mainly for research application. Analytical methods are available for detecting alkylphosphates, carbamates, pyrethroids, chlorinated hydrocarbons, some herbicides and fungicides, chlordimeform, chlorobenzilate, dichloropropene, dinitrocresol and pentochlorophenol or their metabolites in urine or blood. However, due to lack of significant dose-response or dose-effect relationship, the majority of these determinants can only be used as biological exposure indicators to confirm exposure or to estimate internal dose. Further research in developing adequate indicators and methods for biological monitoring of occupational pesticides exposure is needed. Pre-exposure value and/or reference value of relevant indicators are necessary for assessing the degree of exposure and absorption.

Effects of chlordane on parameters of liver and muscle toxicity in man and experimental animals

An attempt was made to compare the toxic effects of the organochlorine insecticide 'chlordane' in man and rats. Analysis of blood for chlordane metabolites showed their presence in the descending order of trans-nonachlor, oxychlordane, heptachlorepoxide and cis-nonachlor. The total range of chlordane and its metabolites in the sera of workers was 9.84 +/- 4.47 ng/g. Serum levels of triglycerides (TG), creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) activities were also found to be higher in pest-control operators. In a simultaneous study, rats were administered 100 mg/kg body wt. of chlordane by stomach tube once a day for 4 days, whereas 50 mg/kg body wt. of chlordane was injected intraperitoneally once a day for 4 days. The data show that total cholesterol and serum TG as well as CPK and LDH activities are increased after chlordane treatment. The isoenzyme patterns suggest that an increase in CPK and LDH is related to skeletal muscle. Furthermore, the hepatotoxicity of chlordane was also studied in rats only. A significant increase in liver weight, its water content, total lipids, triglycerides and phospholipids was recorded. Chlordane induced lipid peroxidation in the liver, exhibiting a dose-response relationship. Although no appreciable effect on mitochondrial function and latent ATPase activity was observed, 2,4-dinitrophenol-stimulated ATPase activity was inhibited. Histological examination of the liver confirmed fatty infiltration induced by chlordane in rats.

Multi-route exposure assessment and biological monitoring of urban pesticide applicators during structural control treatments with chlorpyrifos

A preliminary study of dermal and respiratory exposure to chlorpyrifos (Dursban TC) during structural treatments was conducted with eight workers from a commercial pest control company. The compound was applied by sub-slab and soil injection to four houses, with each application involving two workers. Crawl space applications were included in three of the jobs. Field sampling extended over the entire workday, and included personal air samples and dermal exposure evaluation with patches and handwashes. A fluorescent tracer was added to the formulation for qualitative determination of skin deposition patterns. Pre-exposure and complete 72 hour urine samples were also collected. Total dermal exposure averaged 5.94 mg/hr. The major contributors were the upper legs (38%) and the forearms (34%). Accidents occurred during two of the four applications observed, and the two workers involved in the accidents were the most highly exposed individuals. The mean estimated absorbed daily dose was 9.5 ug/kg/day, with approximately 73% contributed by the dermal route. Thus, under these work conditions the Threshold Limit Value is not an appropriate guide for worker safety. The principal urinary metabolite of chlorpyrifos, 3,5,6-trichloro-2-pyridinol, was found in measurable quantities in all urine samples. Urinary metabolite levels collected 24-48 hr postexposure were highly correlated (R2 = 0.86) with total absorbed dose estimates. The high variability among individual excretion patterns suggests against the use of urine spot sampling, but longer collections may prove useful in the development of a Biological Exposure Index for chlorpyrifos.