Title: Introduction to Radio Frequency Radiation
1Introduction to Radio Frequency Radiation
- Robert Curtis, USDOL/OSHADirectorate of Science,
Technology and Medicine - March 2003
2Health Effects and Standards
3Frequency and Wavelength
4Electromagnetic Spectrum
5How RF Transfers
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7Specific Absorption Rate
- Measure absorbed power in watts per kg of tissue
- Basis of most RF standards
8A Quick Review of RFMW Biological Effects (II)
- Immune (animals only) - T lymphocyte activity
alteration _at_ 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
9A 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 _at_
gt0.02 W/kg 200 591 MHz, but not _at_ 2450 MHz - Mutations - Mutations not found in replicated
studies to date
10A Quick Review of RFMW Biological Effects (III)
(cont.)
- Reproduction - (animals only)
- Temporary make sterility _at_ 5.6 W/kg
- Testicular changes _at_ 15 W/kg
- Leutenizing hormone changes _at_ gt2 W/kg
- Teratology (animals only) - Malformed offspring
found _at_ 31 W/kg, strong thermal dependance (temp
gt41C) - Thermoscoustic - (Pulsed only)
11A 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 _at_ 0.6 W/kg (0.45 W/kg NOEL, brain SAR 2 W/kg
for effect)
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13Basis of RF Standards
- Behavioral disruption threshold
- Limit temperature increase to 1 degrees C
- 1-4 W/kg SAR
- 10-fold safety factor
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15Maximum Permissible Exposure (MPE) for
Occupational (Controlled) Environment
16Same 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.
17Maximum Permissible Exposure (MPE) for Public
(Uncontrolled) Environment
18Maximum Contact Current for Occupational
(Controlled) Environment
19Maximum Contact Current for Public (Uncontrolled)
Environment
20RF 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
21Spatial 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.
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23Microwave Measurement
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31Antenna Equations
32Microwave Applications
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37Cassegrain Antenna
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48Radio Frequency Measurement
49Radio-Frequency MeasurementsIEEE c95.1 - 1991
- gt300 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
50FCC Limits for MPE
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55Spatial Average
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63Single Roof-Top Antenna,various exposure
locations.
64Single Tower, co-located antenna, on-tower
exposure.
65Radio Frequency Applications
- Communication Transmitters
- Industrial Applications
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84RF Safety Programs
85Elements of a Comprehensive RF Protection
Program Role of RF Measurements
86RF Protection Program
- Utilization of RF source equipment which meet
applicable RF standards when new and during its
lifetime. - RF hazard identification and periodic
surveillance by a competent person. - Identification and Control of RF Hazard Areas.
- Implementation of controls and SOPs to reduce RF
exposures to levels in compliance with applicable
guidelines.
87RF Protection Program (cont.)
- RF safety and health training to ensure that all
employees understand the RF hazards and control
methods used. Employee involvement in the
structure and operation of the SH Program. - Implementation of an appropriate medical
surveillance program. - Periodic (e.g. annual) reviews of the program to
identify and resolve deficiencies.
88RF Protection Program (cont.)
- Assignment of responsibilities, including
adequate authority and resources to implement and
enforce the program.
89Notice
90Caution
91Warning
92RF Symbols
- RF energy advisory symbol and RF electric current
hazard advisory symbol.
93Symbols (cont.)
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95Summary of Contact Current