Near real-time monitoring of potential dermal exposure during backpack herbicide spraying

Backpack spraying of herbicides was examined using a near real-time methodology to characterize the potential for dermal exposure to the spray applicator. Spraying was performed under typical field research conditions on corn and soybean plots during the early growing season. Water-sensitive paper strips, which stain blue upon impingement of spray droplets, were attached uniformly to the applicator on six regions of the body (ankle, midcalf, midthigh, waist, chest, and forearm). Significant exposure was observed on the lower half of the body (ankle, calf, thigh), while the amounts collected on the upper half were minimal. Effects of wind speed and wind orientation to the applicator were negligible, as tested. The height of the boom above the ground, however, had a significant impact on exposure levels. A boom height of less than 48 cm (19 in.) above the ground decreased the mean exposure by more than 50% when compared to boom heights at or greater than 48 cm (19 in.) (i.e., the lower the boom height, the less the exposure). This study investigated only potential dermal exposure and not actual dermal exposure and absorption; nonetheless, the results are indicative of normal backpack application procedures. The water-sensitive paper strips proved to be an inexpensive and reliable monitoring tool.