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The purpose of this study was to characterize worker exposure to azinphos-methyl (Guthion) over an entire 4-6 week apple-thinning season. Twenty workers from three work sites in the Chelan-Douglas County region of Washington state were recruited for the study. Exposure potential was estimated by dislodgeable foliar residue measurements, and individual exposures were estimated by biological monitoring through urinary metabolites. Measureable azinphos-methyl residues were found on apple foliage at all sites throughout the six-week sampling period, indicating continuous exposure potential (median residue level of 0.5 microgram/cm2). Measurable levels of the urinary dialkylphosphate metabolite, DMTP, were found in virtually all urine samples (limit of detection = 0.04 microgram/mL). Mean DMTP concentrations differed significantly across sites (0.53, 0.29, and 0.90 microgram/mL for Sites 1-3, respectively; analysis of variance, p < .002), and intraindividual variability was much greater than interindividual differences. Group mean DMTP concentrations at each site fluctuated according to foliar residue levels. Measurable DMTP concentrations were found in 9% of reference workers, ranging from 0.04-0.18 microgram/mL. Cholinesterase activity levels monitored with a field test kit were not considered reliable due to temperature changes of the instrument.

Development of a second-generation video imaging technique for assessing occupational skin exposure (VITAE) is described, its performance evaluated, and new procedures for exposure quantification are presented. The current VITAE system has higher resolution in regard to both its picture element array and gray scale when compared with the prototype system. System performance was evaluated during extended field deployment: variability was 3-4% during data acquisition for individual worker evaluation session, and 10% over a 22-day study period. Variabilities attributable to subject positioning and image outlining procedures were 2.7 and 1.2%, respectively. Visual observations of fluorescent tracer deposition on skin were used to classify specific body regions as either exposed of unexposed, and two computer-based classification criteria were tested against the visual classification. These criteria were generally better at minimizing false negative and false positive classification; sensitivity and predictive value reached 95 and 99%, respectively, when analysis was preceded by presampling of a subset of images. Variability in skin pigmentation was found to have a substantial effect on fluorescent tracer qualification, leading to development of new calibration procedures. Standard curves were generated by spotting a range of tracer concentrations on volunteer subjects and quantifying fluorescence with the VITAE system. These data were then grouped either by subject or by the magnitude of the background signal of the unexposed skin. The ability to control for the effects of skin pigmentation was found to be comparable for these grouping methods, indicating that calibration curves can be developed without the creation of a unique curve for each subject.

To select an exposure monitoring protocol for assessing the occupational risk of fungicides in the lumber industry, the main strategies for determining exposures for risk assessment were reviewed. A survey of lumber industry work sites using fungicides observed the methods of application and opportunities for exposure. In addition, a review of existing measurement data was done. These investigations indicated that fungicide application techniques and process locations were varied from site to site, such that it would be extremely difficult to select a few representative locations for quasi-experimental studies, as is usually done in agricultural pesticide exposure assessment. Existing measurement data mainly describe exposures to fungicides no longer in use, and do not cover the range of application techniques or process technology observed in the survey. A probability sample of the exposed population was therefore proposed.

This study was designed to develop standard procedures whereby the removal efficiency of handwash techniques can be determined. A known amount of the insecticide chlorpyrifos (Dursban), was transferred to the hands of volunteers, which were washed by a standard technique. The following experimental variables were studied: time between exposure and washing, washing solvent, and skin loading. Ethanol removed only 30% of the chlorpyrifos on skin at loadings of approximately 7 micrograms/cm2, with residence time on skin having no effect. Prewashing with ethanol increased removal efficiency. A 10% isopropanol/distilled-water wash removed 43% immediately following exposure, and 23% one hour post-exposure, with skin loadings of approximately 12 micrograms/cm2. Removal efficiency immediately following contact decreased for lower skin loading levels (21-23% for loadings of 0.1-1 micrograms/cm2). These findings indicate that substantial amounts of the insecticide were either absorbed through or adsorbed to the skin, and that pesticide residue levels recovered by standard handwashing techniques are unlikely to represent accurate estimates of dermal exposure. Approximately two-fold to five-fold underestimations of exposure can occur for pesticides with handwash procedures similar to those tested. All experimental variables studied can each alter significantly the fraction of total pesticide on skin that handwashing removes. If handwashing is to be used to estimate dermal exposure in the workplace, appropriate laboratory-based removal efficiency studies should be conducted prior to field investigations. Further efforts should be made to develop accurate and reproducible hand measurement techniques.

Laboratory and field evaluations were conducted to determine the suitability of employing a fluorescent tracer in conjunction with video imaging analysis to measure dermal exposure during pesticide applications. The Fluorescent Whitening Agent 4-methyl-7-diethylaminocoumarin and the organophosphate malathion were highly correlated (r = .985) when sprayed under controlled conditions. Deposition levels during field studies were correlated similarly (r = .942); however, variability in deposition ratios requires that field sampling be conducted to determine the ratio for a particular application. Penetration of the two compounds through cotton/polyester workshirt material demonstrated a high correlation (r = .979), whereas penetration of cotton/polyester coverall material was more variable (r = .834). The slopes of the regression lines for the two materials were not significantly different. The ratio of pesticide and tracer recovered from targets was consistently higher than the initial tank ratio due to differences in solubility and mixing.

Nineteen workers conducting mixing and high-volume airblast applications of the organophosphorus pesticide malathion were monitored simultaneously by biological monitoring and fluorescent tracer evaluation of dermal exposure. Complete 72-hr urine samples were collected and analyzed for dimethylthiophosphate and dimethyldithiophosphate metabolites. Dermal exposure was measured through the addition of a fluorescent tracer to the tank mix, subsequent examination of the skin surface under long-wave ultraviolet light, and fluorescence quantification with a video imaging system. Dermal exposure to applicators was correlated highly with total metabolite excretion (r = 0.91). Mixer exposure was not correlated significantly (r = 0.73) because of wide scatter in the data and the small number of workers monitored. Applicator exposures were more than 3 times higher than mixer exposures, reflecting the high exposure potential inherent in airblast spraying. Exposure to regions protected by gloves or clothing was more than 75% of total exposure for both mixers and applicators. These results provide evidence that the fluorescent tracer technique is a valid methodology for measuring relative levels of dermal exposure during agricultural work activities. The technique also holds promise as a quantitative procedure for evaluating the effectiveness of engineering control strategies and protective clothing performance.

A new method for measuring dermal exposure has been developed which employs video imaging technology and fluorescent tracers. Workers are examined under long wave ultraviolet light following exposure, and fluorescence is quantitated by a television camera interfaced to a microcomputer. This instrument demonstrates high stability over extended periods of use. Through proper calibration it can quantitate a wide range of fluorescent tracer densities on the skin accurately. The lower limit of detection is 100 ng/cm2. Quenching occurs when very high levels of fluorescence are detected, creating an upper limit to quantitation.