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Evaluating Compliance with FCC Guidelines for Human Exposure to Radio Frequency Electromagnetic Fields, OET Bulletin 65
 
Supplement A to OET Bulletin 65, Additional Information for Radio and Television Broadcast Stations

 

Supplement B to OET Bulletin 65, Additional Information for Amateur Radio Stations

 

Supplement C to OET Bulletin 65, Additional Information for Evaluating Compliance of Mobile and Portable Devices with FCC Limits for Human Exposure to Radiofrequency Emissions

 

FCC Regulations

The FCC updated its RF safety regulations in 1997. The regulations require that all transmitting sites in the United States must meet all aspects of these regulations as of September 1, 2000.
The FCC Regulations are based on setting limits for human exposure. The FCC limits are similar to, but not identical, to the limits of several other major standards. There are two sets of exposure limits.

The FCC adopted the first frequency-dependant standard, ANSI C95.1–1982, in 1986. In April 1993, the FCC issued a Notice of Proposed Rule Making (Docket 93–62), indicating that it planned on adopting the new IEEE standard. After three filing extensions, more than 3,000 pages of comments, and a long delay caused by the EPA's planned development of a standard (which was later abandoned), the FCC finally issued its new regulations on August 5, 1996. The new regulations are actually a hybrid, drawing primarily on the 1986 NCRP Report 86 (paragraph “D”) for its field limits, but borrowing certain aspects of the 1991 IEEE standard (paragraph “C”). The FCC made much of the fact that this is the first standard in the United States that is publicly supported by all of the major federal health agencies—EPA, OSHA, and NIOSH. The implementation date was delayed from January 1, 1997, to September 1, 1997, and was delayed again to October 15, 1997. Requirements were phased in for existing sites through September 1, 2000.

The FCC abandoned its long-anticipated plans to adopt the popular IEEE C95.1–1991 standard due to severe criticism from the EPA. Although the EPA abandoned their plans to issue a new set of recommendations of their own, it made its position very clear. The area of the new IEEE standard that the EPA objected to the most was the relaxation of the limits from ANSI C95.1-1982's 5 mW/cm2 at frequencies above 1.5 GHz to the IEEE’s 10 mW/cm2 at frequencies above 3 GHz. The FCC did not want to appear to be opposing the federal government's leading health agency, even though most of the country had adopted the IEEE standard or one of its clones. The EPA does support the addition of limits for induced and contact currents, which the FCC had intended to add in the future. However, due to the political nature of the organization and the change in personnel, this seems unlikely.

The FCC is required by the National Environmental Policy Act of 1969, among other things, to evaluate the effect of emissions from FCC-regulated transmitters on the quality of the human environment. The official regulations document is a Report and Order. In addition, the FCC's Office of Engineering and Technology (OET) has issued Bulletin No. 65 Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields. This is a guidance document—not the regulations! However, OET Bulletin No. 65 has a great deal of practical information, while the regulations can be difficult to follow. See Radio Frequency Safety in the OET section of the FCC Web site. www.fcc.gov/oet/rfsafety/

There are three supplements to Bulletin No. 65.

  • Supplement A provides additional information for radio and television broadcast stations

  • Supplement B provides additional information for amateur radio broadcasters

  • Supplement C covers testing and evaluation of portable and mobile devices.

The FCC Regulations are based on setting limits for human exposure. There are two sets of exposure limits.

  • Occupational/Controlled

  • General Population/Uncontrolled

These are Maximum Permissible Exposure (MPE) limits averaged over the body and averaged over time. The Occupational/Controlled limits are five times higher than the General Population/Uncontrolled limits at all frequencies above 3 MHz. The averaging period for Occupational/Controlled exposure is six minutes for exposure to frequencies below 15 GHz. The averaging time decreases as the frequency increases from 15 GHz to 300 GHz. It is important to note that the FCC does not allow time averaging for General Population/Uncontrolled exposure. The MPE limits are the same for both the electric field and the magnetic field.

The FCC provides definitions for the two types of exposure and attempts to define when they apply. A simplified view, endorsed by the Occupational Safety and Health Administration (OSHA), is that the more restrictive General Population/Uncontrolled limits apply unless:

  • the organization is operating under a written RF safety program, and

  • the individuals who may be exposed to levels above the General Population/Uncontrolled limits have received RF safety training.

A planned Notice of Proposed Rulemaking is aimed at further defining when an organization is allowed to use the higher MPE limits for Occupational/Controlled exposure. The terms fully aware and exercise control are referred to in the current FCC Regulations when defining the requirements for determining whether an exposure situation qualifies to use the higher MPE limits for Occupational/Controlled exposure. The Notice further defines these two important terms.

The phrase fully aware refers to workers who

  • have received both written and verbal information regarding RF radiation.

  • have received training that includes how to control or mitigate RF radiation exposure.

The phrase able to exercise control refers to workers who

  • understand how to use administrative controls to reduce their exposure level. Administrative controls include time averaging.

  • understand how to use engineering controls to reduce their exposure level. Engineering controls include Personal Protective Equipment (PPE), specifically RF personal monitors and RF protective clothing.


Electric Field Limits

The FCC’s MPE limits for the two classes of exposure are shown in the tables below. Limits are spatially averaged over the whole body. The Occupational/Controlled limits are time averaged over 6 minutes. Time averaging is not allowed for the more restrictive General Population/Uncontrolled exposure MPE limits.

MPE Limits for Occupational/Controlled Exposure
Frequency (MHz) Power Density (mW/cm²)
0.03–1.34 100
1.34-30 900/f²
30–300 1.0
300–1,500 f/300
1,500–100,000 5.0

 

MPE Limits for General Population/Uncontrolled Exposure
Frequency (MHz) Power Density (mW/cm²)
0.03–1.34 100
1.34–30 180/f²
30–300 0.2
300–1,500 f/1500
1,500–100,000 1.0

 

Magnetic field limits are higher below 100 MHz.

Induced and Contact Current Limits

Although the FCC announced plans to issue exposure limits for induced and contact currents when the field strength limits became effective in 1997, there has been no further action taken. Part of the problem is the difficulty in making the measurements. It is far more difficult to make current measurements than field strength measurements, and the lack of interest led the major manufacturer of such equipment, Narda Safety Test Solutions, to discontinue its series of current measurement products. The lack of suitable equipment, the difficulty in making measurements, and the change in personnel at the FCC makes the issuance of additional RF safety regulations unlikely.