title: Foot currents and ankle SARs induced by dielectric heaters.
abstract: 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.
authors.affiliation: Physical Agents Effects Branch, National Institute for Occupational Safety and Health, Cincinnati, Ohio 45226-1998.
authors.forename: D L
authors.initials: DL
authors.lastname: Conover
authors.forename: C E
authors.initials: CE
authors.lastname: Moss
authors.forename: W E
authors.initials: WE
authors.lastname: Murray
authors.forename: R M
authors.initials: RM
authors.lastname: Edwards
authors.forename: C
authors.initials: C
authors.lastname: Cox
authors.forename: B
authors.initials: B
authors.lastname: Grajewski
authors.forename: D M
authors.initials: DM
authors.lastname: Werren
authors.forename: J M
authors.initials: JM
authors.lastname: Smith
mesh_terms: D000842:Ankle; D004553:Electric Conductivity; D004574:Electromagnetic Fields / Q000009:adverse effects*; D005528:Foot; D006361:Heating / Q000295:instrumentation*; D006801:Humans; D016273:Occupational Exposure