Module 3 - Extremely Low Frequency Radiation Safety

Whenever a current passes through a wire, a magnetic field is produced. Because electric power generation in the United States changes polarity at 60 Hz (cycles per second), the magnetic fields generated also alternate at 60 Hz. Since about 1980, these 60 Hz magnetic fields (and their frequency harmonics) have been suspected of causing various types of negative health effects. These magnetic fields are commonly called extremely low frequency (or ELF) fields.

The most accurate answer is that no one really knows. Although some health effects have been statistically related to ELF exposure, these effects are poorly understood and may exist only as statistical or scientific errors. Some research studies, which originally indicated ELF health effects, could not be duplicated. Much of the data supporting effects is from epidemiological studies and the effects found were slightly outside the boundaries of statistical error. What can be determined from this information is that any real effect (and the corresponding hazard) must be relatively small.

In the absence of conclusive data, the International Radiation Protection Association/International Non-Ionizing Radiation Committee (IRPA/INIRC) has produced an interim exposure guideline. Although the US Government and the State of California have no regulations on exposure to ELF, UC Berkeley has adapted the IRPA/INIRC guidelines in order to address employee concerns.

Occupational Limits

Non-OCCUPATIONAL LIMITS

^{* The duration of exposure to fields between 10 and 30 kV/m2 may be calculated from the formula t 0 E, where t is the duration in hours per workday and E is the electric field strength in kV/m2.}

^{** Maximum exposure duration is 2 hours per workday.}

^{*** This restriction applies to open spaces in which members of the general public might reasonably be expected to spend a substantial part of the day, such as recreational areas, meeting grounds, and the like.}

^{**** These values can be exceeded for a few minutes each day provided precautions are taken to prevent indirect coupling effects.}

Since even the wiring for electric lights will generate ELF magnetic fields, these fields are present in virtually every room of every building on campus. The ELF field intensity is a function of the amperage passing through the wiring. In general, transformers and large motors will produce the most intense fields. Mechanical spaces and machine shops normally have the most intense fields and these may (rarely) exceed the non-occupational exposure limit. Laboratories and offices usually do not have intense fields and a reasonable average value for these areas has been measured at about 3 to 5 mG (milliGauss). So normally, the ELF fields UC Berkeley employees are exposed to are less than 1% of the non-occupational exposure limit.

Radiation Safety is available to address questions on ELF exposure. A number of training documents are available to explain what is (and is not) known about ELF exposure and health effects. Please contact EH&S if you would like copies of these documents.

EH&S is also available, upon request, to perform ELF surveys of specific equipment or work areas. Survey reports will characterize the ELF field intensity in the areas surveyed, but cannot specifically address the hazards of fields found to be in excess of the IRPA/INIRP Guidelines.

EH&S will normally recommend that exposure to fields in excess of the guidelines be mitigated so as to prevent exposure above the IRPA/INIRP Guidelines to employees or students. Since there is no legal requirement to control ELF exposure, the implementation of such recommendations is at the discretion of the Department.