A video imaging technique for assessing dermal exposure. II. Fluorescent tracer testing.

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.

A video imaging technique for assessing dermal exposure. I. Instrument design and testing.

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.

The relationship between dermal pesticide exposure by fruit harvesters and dislodgeable foliar residues.

Dermal pesticide exposure rates, expressed in mg/hr, by strawberry and blueberry harvesters and dislodgeable foliar pesticide residues were determined in 7 separate field experiments during 1981-1983 in California and Oregon. The pesticides which were studied included captan, vinclozolin, carbaryl, and methiocarb. A positive correlation between these two parameters was found and compared with literature values involving different pesticides and tree crops. The ratio between dermal exposure rate and dislodgeable foliar residues, the units of which are area/time, may have a possible use as an empirical factor for a first approximation of dermal exposure rates by fruit harvesters without the involvement of human subjects.

Correlation of urinary pesticide metabolite excretion with estimated dermal contact in the course of occupational exposure to Guthion.

Exposure to and absorption of Guthion 50 W.P. (azinphos-methyl) were estimated in orchardists from the Okanagan Valley in British Columbia who were involved in mixing, loading, and application with ultra-low volume air blast equipment. Air monitoring and patch techniques were used to estimate exposure, and alkyl phosphate excretion and cholinesterase inhibition were measured to estimate absorption. All workers were issued with standardized cotton shirts, trousers, and long-sleeved coveralls. All wore half-face respirators, gloves, boots, and hats. Eight wore rubberized protective clothing in addition. The indirect method of measuring urinary metabolites appeared to be the most sensitive. All workers had quantifiable levels of alkyl phosphates following exposure, and 24-h urine samples provided a more reliable estimate than first morning voids. A high correlation was observed between 48-h alkyl phosphate excretion and amount of active ingredient sprayed. A fluorescent tracer was added to the tank along with the Guthion. The finding of Guthion on patches beneath the clothing was confirmed by the presence of the tracer on the skin. With the ultralow-volume application used in this study, the rubberized clothing did not appear to be significantly more protective than the heavy coverall. There was no significant depression of either red blood cell or serum cholinesterase activity in any workers.

Harvester exposure to Zolone (phosalone) residues in peach orchards.

This field study was undertaken to quantitate the exposures of peach pickers to pesticide residues. Five fields were harvested each for three days at decreasing post-application intervals. Aerosol and dermal exposure estimates indicated 98-99% of the workers' dose was dermal, predominantly to the hands and upper extremities. Estimates of dose correlated with measurements of foliar residues. Despite estimated dose rates of up to 14 mg/hr, the RBC cholinesterase in these workers may have been only slightly inhibited (circa 4%) when compared to an unexposed, control population. Comparisons of these results with earlier studies of parathion residues on citrus indicate a consistent pattern of worker exposure. However, a concern is raised over the efficacy of using existing foliar residue sampling methodologies for all other pesticides.

The persistence of ethion and zolone residues on grape folliage in the central valley of California.

The hazard of serious intoxication of agricultural field workers by organophosphate insecticide residues has led to the establishment of reentry intervals in California. In the attempt to extend this concept nationally, it has been found that there is a lack of relevant field data for setting of such standards. In an effort to expand knowledge of the relationship between foliar residue levels and occupational hazard, an examination of the persistence and transport of ethion, Zolone, and their oxygen analogs on grape foliage was conducted. Both dislodgeable and penetrated residues were followed for 28 days post-application for both insecticides while soil surface residues were followed for ethion only. A marked difference is seen in the decay rates of the dislodgeable vs. the penetrated residues of ethion, the dislodgeable residues decaying more quickly. This difference is not apparent for Zolone. Of particular significance to worker hazard is the finding that the oxones of both ethion and Zolone in the dislodgeable residues reach a plateau after approximately seven days and do not degrade further by day 28.