The modern world is full of devices that, either directly or indirectly, act as sources of non-ionizing radiation (NIR). These sources produce NIR in the electromagnetic spectrum of wavelengths/frequencies ranging from 100 nm to static fields. Many NIR sources are present on the UC Berkeley campus, either in research applications or in ancillary equipment.
In general, NIR tends to be less hazardous to humans than ionizing radiation (ionizing radiation has a wavelength of less than 100 nm or a photon energy greater than 12.4 electron Volts). However, depending on the wavelength/frequency and the irradiance (or power density) value, NIR sources may present a human health hazard. This manual is intended to provide guidance in maintaining a safe NIR work environment on the campus.
Non-Ionizing Radiation Safety Policy
It is the policy of the University of California at Berkeley to provide a workplace safe from the known hazards of NIR by assuring compliance with federal and state safety regulations. Presently, it is not clear if Extremely Low Frequency (ELF) Radiation poses any hazard to human health. However, the ICRP Interim Guidelines on Limits to 50/60 Hz Electric and Magnetic Fields are used by the campus as a precaution. The NIR safety program is upgraded as new regulations and standards become available.
This policy applies to all persons exposed to NIR hazards on UC Berkeley property. The UC Berkeley Office of Environment, Health & Safety (EH&S) has been assigned responsibility for implementing the NIR safety policies established by the campus Non-Ionizing Radiation Safety Committee (NIRSC).
NOTE: Ionizing radiation, lasers, and coherent light sources are not covered in this manual. For information on the hazards from these sources, see the campus Radiation Safety Manual, the Laser Safety Manual, and the Laser Safety Training Supplement. Please contact EH&S to obtain these documents or additional information.
Applicable Regulatory Standards & Guidelines
Non-coherent UV, Visible, Infrared Radiation
Title 8 - CCR, ACGIH, ANSI Z136.2
|Microwave/Radio Frequency Radiation||FCC OET 65, IEEE C95.1, Title 8 - CCR, ACGIH|
|Extremely Low-Frequency Radiation||IRPA/INIRC - NIR Protection Guidelines|
|Static Magnetic Fields||ACGIH|
The California Code of Regulations (CCR, Title 8, Section 5085, Subchapter 7, Group 14, Article 104 – Nonionizing Radiation) establishes MPE (maximum permissible exposure) values for frequencies between 3 MHz and 300 GHz. At present, neither the state nor federal government regulates those frequencies below 3 MHz. The Institute of Electrical and Electronics Engineers (IEEE) C95.1 (1991) Standard recommends MPE values for frequencies between 3 MHz and 3 kHz. This standard is a revision of the American National Standard Institute (ANSI) C95.1 (1982) and is recognized by ANSI as the standard of safety practice.
The International Radiation Protection Association/International Non-Ionizing Radiation Committee (IRPA/INIRC) has published Interim Guidelines on Limits to 50/60 Hz Electric and Magnetic Fields. These guidelines are intended to limit the potential health effects of extremely low frequency (ELF is all frequencies below 3 kHz) radiation exposure. IRPA/INIRC recommends a continuous MPE of 1000 mG (0.1 mT) for exposure to uncontrolled environments over a lifetime. This standard agrees with the permissible magnetic flux exposure for persons wearing cardiac pacemakers recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). NOTE: The ACGIH recommends the electrical field for persons wearing cardiac pacemakers not exceed 1.0 kV/m.
The Federal Communications Commission (FCC) publishes the OET 65 Standard which provides guidance on protection of workers and the public from microwave/RF radiation emissions from transmission towers and other broadcast facilities. The American National Standards Institute (ANSI) publishes the Z136.2 Standard for the Safe Use of Optical Fiber Communications Systems Utilizing Light Emitting Diodes.
Compliance with CCR Title 8 is required for all employers in the state of California. Enforcement of these regulations falls to Cal-OSHA, who inspects campus facilities to determine compliance with Title 8. Although the IEEE Standard is not a regulation, it does "...represent a consensus of the broad expertise on the subject within the institute..." and is commonly accepted within the United States as the safety guidance for frequencies between 3 MHz and 3 kHz. The IRPA Interim Guideline is the best guidance available on ELF safety that is based on international scientific consensus. The Swedish government has established a performance-based emission standard for computer monitor manufacturers (the MPR-II Standard allows a MPE of 2.5 mG), but the safety need for this standard has not been accepted by the international scientific community.
Understanding and Evaluating Non-Ionizing Radiation Hazards
The properties and hazards of NIR can best be understood by considering the EM spectrum as three broad categories:
- Optical radiation (100 nm to 1 mm)
- Microwave radiation (300 GHz to 300 MHz)
- Radiofrequency and lower frequency radiation (300 MHz to Static Fields)
Basic characteristics of optical radiation (ultraviolet/visible light/infrared):
- Possess small wavelengths, large frequencies, and substantial energy (extreme UV approaches the photon energy of ionizing radiation).
- Optical theory can be applied to an analysis of the radiation field.
- Both thermal and photochemical (biological) effects are possible from exposures (depending on wavelength).
- Exposures normally occur in the far field where the E (electric) and H (magnetic) fields are strongly coupled.
- The inverse square law applies to any analysis of the radiation field.
- Only power density (S) measurements are normally considered in the hazard analysis.
- The radiation interacts readily with surfaces and can easily deposit energy in human tissues.
Basic characteristics of microwave radiation (300 GHz to 300 MHz):
- Possess intermediate wavelengths (1 mm to 1 m), frequencies, and moderate photon energy.
- Microwave theory can be applied to an analysis of the radiation field.
- Both thermal and induced current (biological) effects are possible from exposures.
- Exposures may occur in both the near and far fields.
- In hazard analysis, both E (electrical field) and H (magnetic field) measurements must be considered in addition to the power density (S) measurements.
- This type of radiation resonates (forms standing waves) in tissue dimensions with multiples of 1/2 wavelength (depending on the tissue orientation to the wave plane).
Basic characteristics of Radiofrequency and lower frequency (ELF, static) fields:
- Possess large wavelengths (>1 m), small frequencies, and very low energy.
- Circuit theory can be applied to an analysis of the radiation field.
- In general, there is poor energy deposition in human tissue but thermal and induced current (biological) effects are possible.
- Exposures usually occur in the near field where the E and H fields are not coupled.
- The inverse square law may not apply.
- The E and H measurements must be considered separately for a hazard analysis (of RF).
- At ELF and static fields, the magnetic field dominates the hazard analysis.
- This type of radiation can easily penetrate, but rarely deposit energy in tissue.