Sources of Exposure Data
AHETF reviewed over 200 existing exposure studies for possible inclusion in its database. The reviews followed strict acceptance criteria for a generic database that was approved by the regulatory agencies. Twenty (20) studies that were deemed acceptable were acquired from the data owners and then combined with studies conducted by AHETF which monitored more than 500 workers as they mixed, loaded, and/or applied pesticides as part of their normal work practices. AHETF exposure studies were conducted according to established regulatory guidelines for exposure studies, the Good Laboratory Practice (GLP) standard, and all applicable ethical requirements.
Passive dosimetry techniques were used in determining the amount of pesticide residue on worker skin and available to be inhaled during a normal work day by employing the following methods.
- Exposure to the skin of arms, legs, and torso was determined by having the workers wear a one-piece, all cotton union suit under their normal work clothing. These inner dosimeters were collected at the end of the day and sectioned into various body parts for residue analysis. The inner dosimeter served as a surrogate for the amount of residue that would ordinarily penetrate through a single layer of clothing to the skin.
- In cases where significant residues might be deposited on feet, such as with applications with hand-held equipment, the workers wore a new pair of cotton socks inside their boots for determining potential foot exposure.
- Exposure to the hands was determined by having the workers wash their hands with a mild surfactant solution (often after removing chemical-resistant gloves that were worn during the handling task).
- Exposure to the head area was determined by wiping the face and neck area with cotton gauze pads moistened with a mild surfactant solution. In cases where workers were required to wear chemical resistant head gear, cotton patches were also placed inside and on top of the head gear, allowing the determination of head exposure both with and without the presence of the head gear.
- Potential inhalation exposure was determined by placing an air sampling device containing a filter and sorbent material in the breathing zone of the workers. A pump, attached to the worker’s belt, drew air through the sampling device at a rate of 2 L/Min. The amount of residue on the filter and sorbent material was a measure of potential inhalation exposure.
For prediction purposes, the amount of residue measured on each matrix after a single work day was normalized by dividing the amount of active ingredient handled by the worker and expressed as µg/lb ai. Normalized total dermal exposure was then calculated by summing the values from all matrices.