Contribution of aerosols generated during mixing and loading of pesticidesto operator inhalation exposure

The occupational exposure resulting from the application of crop protection agents continues to be of great interest for the purposes of identifying h azards or determining safer chemical handling methods. The purpose of the p resent study was to identify the potential respiratory exposure of a mixer/ loader to chlorothalonil, with the mixing and loading operation as the only source of aerosols (particles < 13 mu m diameter). Three worst-case mixing /loading scenarios were simulated in the lab: (1) a spill of undiluted chlo rothalonil formulation onto a dry, horizontal metal surface; (2) a spill of undiluted chlorothalonil formulation onto a rapidly rotating shaft; and (3 ) pouring undiluted chlorothalonil formulation into a container of water. A erosol generation from these scenarios was compared to that resulting from atomizing dilute chlorothalonil through hydraulic nozzles. Aerosols were ca ptured with a cascade impactor, and quantified by gas chromatography. Resul ts indicated that simulated spill scenarios generated aerosol concentration s between 2.1 and 5.3 ng/l, which were in the same order of magnitude as, a nd only marginally higher than, the detection threshold (1.7 ng/l) and back ground levels (2.2 ng/l). In comparison, atomization of dilute chlorothalon il through a hollow cone and flat fan nozzles resulted in airborne concentr ations of 354 and 96 ng/l, respectively, related to the atomization charact eristics of these nozzles. Measurement of the dimensions of the aerosol clo ud indicated that aerosols resulting from a spill amounted to approximately 10(-5)% of the spilled chlorothalonil. It was estimated that a male worker respiring 29 l/min would inhale approximately 0.32-0.78 ng of chlorothalon il during a typical 30 s spill, assuming a 1%, transfer efficiency between the spill site and the mixer/loader. These estimates were between 10 000 an d 480 000 times less than literature data for respiratory exposure of chlor othalonil by applicators and harvesters, suggesting that inhalation of aero sols from mixing and loading represents a minor component of overall exposu re. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.