Passive dosimetry

Comparison of exposure levels — total absorbed dose of chlorpyrifos (passive dosimetry vs. urinary monitoring)... 

The described method of simultaneously measuring the total absorbed dose by passive dosimetry and biomonitoring shows excellent reproducibility over a range of four states, six worker types, and a range of 84 test replicates (one replicate = one volunteer). 

Collectively, the data from Table 7 and Figures 1 through 3 lead to the conclusion that concurrent biomonitoring and passive dosimetry techniques can be achieved and are not divergent worker exposure assessment methods. The correlation between exposure levels measured by these methods is quite good. 

Assessments of risks associated with the use of chlorpyrifos insecticide products for workers have been made. The assessments are based on the results of field studies conducted in citrus groves, a Christmas tree farm, cauliflower and tomato fields, and greenhouses that utilized both passive dosimetry and biomonitoring techniques to determine exposure. The biomonitoring results likely provide the best estimate of absorbed dose of chlorpyrifos, and these have been compared to the acute and chronic no observed effect levels (NOELs) for chlorpyrifos. Standard margin-of-exposure (MOE) calculations using the geometric mean of the data are performed however, probability (Student s f-test) and distributional (Monte Carlo simulation) analyses are deemed to provide more realistic evaluations of exposure and risk to the exposed population. 

The results from the several studies that have been conducted to measure exposures associated with the use of chlorpyrifos are summarized in Tables 1 and 2. Table 1 summarizes results from mixer-loader and applicator studies reported by Honeycutt et al.1 Listed for each work description are the number of replicates, the arithmetic mean, and the geometric mean for the replicates from both the passive dosimetry measurements and the biomonitoring tech-... 

Major questions that arise whenever a pesticide exposure evaluation is completed are how good are the data and how close to the real answer have we gotten For most commercially sold insecticides, there are no appreciable pharmacokinetic data in human systems, although some data normally exist for animal models. Because such pharmacokinetic data do not exist for most active insecticides, passive dosimetry measurements must be used to estimate the exposure and eventually dose. Once such passive dosimetry data exist, certain assumptions must be made to arrive at an estimate of dose. 

Passive dosimetry, which proved useful for the pursuit of better workplace hygiene in agriculture during the past 40 years (Durham and Wolfe, 1962), yields unvalidated and excessive amounts of worker exposure (Krieger, 1996). Currently, our approach with respect to indoor and agricultural exposure assessments has been the evaluation of exposure estimates using well-known, studied chemicals to first understand the work task and at a later time develop chemical-specific studies as required in the regulatory arena. 

If a further refinement of the determination of exposure is necessary, an exposure study using the product of concern and conducted under conditions of real practice might be required. The exposure study may include passive dosimetry or biomonitoring, depending on the properties of the active substance and the data on metabolism and toxicokinetics in mammals. 

From the late 1960s until the early 1980s, a large number of worker exposure studies were reported which used the methods of passive dosimetry — that is, methods that measured potential contact with pesticides but did not measure the actual amount of pesticide absorbed by the workers bodies. These studies were extensively reviewed by Wolfe (1976) and later by Davis (1980). 

In the early 1980s, the whole-body dosimeter (WBD) was introduced as a superior method for passive dermal dosimetry monitoring. A standard protocol was described by the World Health Organization (1982), and Abbott et al. (1987) described some additional options. Chester (1993) reported refinements that permitted exposure estimation by passive dermal dosimetry and biological monitoring simultaneously. 

A Passive Integrating Radon Dosemeter Combining Activated Charcoal and TLD, Radiation Protection Dosimetry, 5, 241-245. 

Urban, M. and Piesch, E., Low Level Environmental Radon Dosimetry with a Passive Track Etch Detector Device, Rad. Prot. Dos. 1 97-109 (1981). 

Khan, A., and C.R. Philips, Electrets for Passive Radon Daughter Dosimetry, Health Phys., 46, 141-149, (1984). 

Zabiegala, B. Kot, A. Namiesnik, J. 2000, Long-term monitoring of organic pollutants in water-Application of passive dosimetry. Chem. Anal-Warsaw 45 645-657. 

Urban, M. Piesch, E. (1981) Low level environmental radon dosimetry with a passive track etch detector device. Radiation Protection Dosimetry, 1, 97-109. 

DiGiano, F.A., D. Elliot, and D. Leith. 1988. Application of passive dosimetry to the detection of trace organics. Environ. Sci. Technol. 22 1365-1367. 

INTRODUCTION 14 PESTICIDE CATEGORIES 15 PESTICIDE HANDLERS 15 Agricultural Pesticide Handlers 15 Tasks Performed by an Individual 16 Factors Affecting Exposure 16 Residential and Institutional Pesticide Handlers 18 Families of Pesticide Handlers 19 STUDY DESIGN CONSIDERATIONS 20 Worker Stratification 21 Routes of Exposure 21 Respiratory Exposure 21 Dermal Exposure 21 Sampling Strategy Selection 21 Statistical Analysis 22 PROTECTION OF HUMAN SUBJECTS 22 PESTICIDE EXPOSURE MONITORING METHODS 23 Passive Dosimetry 23... 

Urinary Metabolite Monitoring 28 Salivary Monitoring 29 VALIDATION OF PASSIVE DOSIMETRY 30 Atrazine 30 Chlorpyrifos 31... 

The two primary methods for assessing exposure to pesticides are passive dosimetry, which is more commonly used, and biological monitoring. 

Several studies using either passive dosimetry or biological monitoring, or both methods, were submitted by the registrant to assess exposure to workers in the US com belt. The details of these studies are found in the USEPA Revised Human Health Risk Assessment (USEPA, 2002) and the USEPA Re-registration Eligibility Document (USEPA, 2003) on atrazine. 

In the USA, the principal use of atrazine is in agriculture, and the major exposed workers are handlers who mix, load and apply atrazine to row crops. The passive dosimetry studies reported atrazine residues in terms of the parent compound only. The biological monitoring studies measured chlorotiazenes metabolites. The atrazine absorbed dose was back-calculated from the measured metabolites based on a human excretion study. The results of the smdies are reported in Table 1.3 and demonstrate fairly close concordance between the two methodologies. 

Table 1.3 Comparison of biomonitoring and passive dosimetry data from atrazine exposure studies using closed mixing/loading systems and closed cabs (USEPA, 2002, 2003)...

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