Foot currents and ankle SARs induced by dielectric heaters.
Data are presented on ankle-specific SARs and foot currents as a function of strengths of radio-frequency electromagnetic fields encountered by operators of dielectric heaters. The determination of foot currents was based on near-field exposures in which reactive coupling dominates, and which can result in substantial SARs in exposed workers. The operators were located less than one wavelength from--usually within one meter of--the dielectric heaters, which generated fields at frequencies from 6.5 to 65 MHz. At distances normally assumed by workers, maximal strengths of electric fields ranged from 10(4) to 2.4 x 10(6) V2/m2; maximal strengths of magnetic fields ranged from 5.0 x 10(-3) to 33.3 A2/m2. Currents through both feet to ground were measured while operators stood where they normally worked. Maximal currents ranged from 3 to 617 mA, rms. Nearly 27 percent of the dielectric heaters induced foot currents that exceeded the 200-mA limit that has been proposed for a new ANSI C95.1 standard. Twenty percent of the heaters induced foot currents that exceeded 350 mA. SARs in ankles were calculated from foot currents, and they approximated 5 W/kg at 100 mA, 29 W/kg at 250 mA, and 57 W/kg at 350 mA. The maximal SAR in the ankle was approximately 176 W/kg at 617 mA.
Conover
D L
DL
Physical Agents Effects Branch, National Institute for Occupational Safety and Health, Cincinnati, Ohio 45226-1998.
Moss
C E
CE
Murray
W E
WE
Edwards
R M
RM
Cox
C
C
Grajewski
B
B
Werren
D M
DM
Smith
J M
JM
D000842:Ankle; D004553:Electric Conductivity; D004574:Electromagnetic Fields / Q000009:adverse effects*; D005528:Foot; D006361:Heating / Q000295:instrumentation*; D006801:Humans; D016273:Occupational Exposure