Introduction to Radio Frequency Radiation

1. Introduction to Radio Frequency Radiation Robert Curtis, USDOL/OSHADirectorate of Science, Technology and Medicine March 2003

2. Health Effects and Standards

3. Frequency and Wavelength

4. Electromagnetic Spectrum

5. How RF Transfers

7. Specific Absorption Rate • Measure absorbed power in watts per kg of tissue • Basis of most RF standards

8. A Quick Review of RFMW Biological Effects (II) • Immune (animals only) - T lymphocyte activity alteration @ 1.4 W/Kg • Blood - no consistent results • Cancer - No specific animal life span study seeking cancer has been done; epl' studies of radio hams, electrical workers, and physical therapists found excess cancer, but other studies have not found association

9. A Quick Review of RFMW Biological Effects (III) • Neurological (animals only) - Test of blood/brain barrier contradictory; unreplicated studies with AM & PM fields show brain metabolism changes @ >0.02 W/kg 200 & 591 MHz, but not @ 2450 MHz • Mutations - Mutations not found in replicated studies to date

10. A Quick Review of RFMW Biological Effects (III) (cont.) • Reproduction - (animals only) • Temporary make sterility @ 5.6 W/kg • Testicular changes @ 15 W/kg • Leutenizing hormone changes @ >2 W/kg • Teratology (animals only) - Malformed offspring found @ 31 W/kg, strong thermal dependance (temp >41°C) • Thermoscoustic - (Pulsed only)

11. A Quick Review of RFMW Biological Effects (III) (cont.) Observed in radar operators in WWII as perceived clicking sound. Possible cause of neurological, central cholinergic, effects observed by James Lai @ 0.6 W/kg (0.45 W/kg NOEL, brain SAR #2 W/kg for effect)

13. Basis of RF Standards • Behavioral disruption threshold • Limit temperature increase to 1 degrees C • 1-4 W/kg SAR • 10-fold safety factor

15. Maximum Permissible Exposure (MPE) for Occupational (Controlled) Environment

16. Same Basis, but Standards Differ • General population vs. Controlled RF Sites • Localized exposure limits (spatial averaging) • Time averaging • Special exclusions, such as low-power devices, peak exposures.

17. Maximum Permissible Exposure (MPE) for Public (Uncontrolled) Environment

18. Maximum Contact Current for Occupational (Controlled) Environment

19. Maximum Contact Current for Public (Uncontrolled) Environment

20. RF Exposure Standards are Typically Based on 6 min. TWA • Excursions allowed if 6 min time weighted average is within limits • Up to 30 min intervals used for public exposure standards

21. Spatial Averaging • ANSI standard is confusing regarding partial-body vs. non-uniform exposure. • Exception for testes and eyes (See interpretation). • OSHA standards, based on old ANSI, does not allow for spatial averaging.

23. Microwave Measurement

31. Antenna Equations • Equation

32. Microwave Applications

37. Cassegrain Antenna

48. Radio Frequency Measurement

49. >300 MHz - E or H or S; spatial average 100 - 300 MHz - E & H; spatial average 3 kHz - 100 MHz - E & H; spatial average; including current; contact current Radio-Frequency MeasurementsIEEE c95.1 - 1991

50. FCC Limits for MPE • Table Notes