Richard A. Fenske

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.

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 (DursbanR 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 post-exposure 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.

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.

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.

Nonuniform dermal deposition patterns during occupational exposure to pesticides.

Dermal exposure to pesticides was characterized by fluorescent tracers, video imaging, and patch sampling during orchard/airblast and greenhouse/handgunner applications. Pesticide deposits on skin and patches were nonuniform over individual body regions. Exposed surface areas of upper body regions of orchard/airblast workers were highly variable, and represented 4–22% of total regional surface areas. Deposition patterns were dependent on work activity and type of application; exposure was highest on the ventral segment of the forearm for mixers, but on the dorsal segment for applicators; exposure to the front of the head was three times higher than to the side of the head for airblast applicators, but three times lower for mixers. Use of different patches to estimate head exposure resulted in two to eight-fold differences dependent on worker activity. Nonuniformity of dermal exposure is the source of substantial uncertainty in exposure and risk assessments of agricultural workers.

Correlation of fluorescent tracer measurements of dermal exposure and urinary metabolite excretion during occupational exposure to malathion

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.

Worker exposure and protective clothing performance during manual seed treatment with lindane

Twelve workers were monitored for exposure to 18.75% lindane dust formulation during manual wheat seed treatment. The mean total actual exposure rate was 32.89 mg/hr. Potential respiratory exposure averaged 0.0057 mg/hr (<1% of the total), with seven workers receiving no measurable respiratory exposures. Mean hand exposure was 1.84 mg/hr (5.6%). Dermal exposure to the head and neck averaged 4.28 mg/hr (13%). Exposure measured beneath the workshirt and workpants averaged 26.8 mg/hr (81.4%). The workshirt and workpants provided 3.4-fold and 11.5-fold protection factors, respectively. Forearm exposure measured beneath the workshirt represented more than 40% of total actual exposure. The small contribution of hand exposure to total dermal exposure was consistent with the use of chemical-resistant gloves by all workers. Total dermal exposure could be reduced substantially by wearing coveralls over regular work clothing, and by the use of gauntlet-type gloves. It is recommended that worker education concerning personal hygiene and the appropriate use of protection clothing be made essential components of exposure reduction programs.

Occupational exposure to fosetyl-Al fungicide during spraying of ornamentals in greenhouses

Eight workers were monitored by the dermal patch/hand rinse technique for exposure to the fungicide aluminum tris-o-ethyl phosphonate [fosetyl-Al or ALIETTE®] during treatment of ornamentals in a greenhouse, using commercial back-pack sprayers. The mean total dermal exposure for mixers was 512 μg a.i./hr and for applicators 389 μg a.i./hr. Mixers had higher exposure to the face and neck (213 μg/hr) than did applicators (115 μg/hr). Workpants provided 4 to 6 times greater protection than workshirts. The highest exposure for both activities was to the forearms. Hand exposure represented only 6% of total exposure, while regions protected by clothing contributed 47% of total exposure for mixers and 60% for applicators. Respiratory exposure contributed 7–9% of total exposure. The high variability in dermal patch results suggests a lack of precision in the sampling methodology, and indicates a need for larger sample sizes.

Comparative assessment of protective clothing performance by measurement of dermal exposure during pesticide applications

Abstract Protective clothing performance was assessed among 25 workers by adding a fluorescent tracer to spray tanks during high-volume airblast applications and measuring dermal exposure to the tracer with a video imaging system. Three types of protective clothing were evaluated: 50/50 cotton/polyester workshirts, 65/35 cotton/ polyester woven coveralls, and nonwoven coveralls (untreated Tyvek[rgrave]). Workers also wore neoprene gloves during all work activities. A substantial portion of exposure beneath clothing occurred near the sleeve and neck openings in the garments. This direct deposition is attributed to air exchange inside clothing due to body worker movements (pumping effects). Hand exposure was measured for all workers and was likely due to contamination during glove removal and handling. Workshirts provided significantly less protection than coveralls during application. No difference in exposure reduction between the two coveralls was demonstrated. The use of coveralls in place of workshirts...

Assessment of Dermal Exposure to Chlorophenols in Timber Mills

Abstract The quantitative assessment of dermal exposure among nine timber mill workers was conducted in conjunction with biological monitoring. A fluorescent tracer was included in a sapstain control application of an aqueous tetrachlorophenol (TCP) formulation in a planing mill. Workers grading and pulling the lumber were examined under longwave ultraviolet light before and after work, and the pattern of fluorescence on the skin was quantitated with a computer-based video imaging system. Urine samples were collected from the workers at the end of the day. Wipe samples and glove monitors were employed to determine the amount of TCP represented by the tracer on the skin. Less than two percent of the TCP applied to the wood was available by wipe sampling 30 seconds later. Six of nine workers received measureable exposure to the hands despite the consistent use of chemical-resistant gloves. All pullers exhibited exposure to the forearms. TCP exposure was highly correlated with time worked (R2 = 0.84). Dermal...