The Effect of Operator Hand Position and Workstation Furniture on Foot Current for Radio Frequency Heater Operators

Abstract

The dependence of foot current on operator hand position and workstation furniture was studied to better assess and reduce operator exposure where reactive field coupling predominates (i.e., 10 to 100 MHz and within 1 m of heaters). Reactive coupling contributions to foot current have not been studied in a systematic manner in the laboratory or the workplace. The measurement of current induced in a worker's extremities (i.e., foot, ankle, arm, and wrist) is the most feasible and accurate method to assess reactive field exposures. A total of 72 measurements was made with four workers who were operating two radio frequency (RF) heaters in a workplace. All measurements were made twice in randomized order. Operator posture/furniture and foot current readings were documented by simultaneous videotape recordings. Foot current was determined as a function of 1) the operator's hand position, and 2) the type of stool used. With one exception, foot current increased when the operator's hands were extended over the heater applicator plates. Videotape recordings documented that one operator had long arms and could easily reach over the plates of one particular heater without leaning toward the heater. In contrast, for all other foot current measurements, the operators had to lean toward the heater to reach over the plates. It was determined that foot current increased as the operator's upper torso was positioned closer to the heater. Thus, administrative controls or physical barriers that keep the operator's body farther from an RF heater can reduce foot current. There was no measurable change in foot current with the type of stool (plastic versus wooden) used. To obtain meaningful exposure evaluations for heater operators, industrial hygienists must determine the dependence of foot current on common hand and upper torso positions.