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and academia after extensive reviews of the scientific literature
related to the biological effects of RF energy.
Many countries in Europe and elsewhere use exposure guidelines
developed by the International Commission on Non-Ionizing
Radiation Protection (ICNIRP). The ICNIRP safety limits are generally
similar to those of the NCRP and IEEE, with a few exceptions. For
example, ICNIRP recommends different exposure levels in the lower
and upper frequency ranges and for localized exposure from certain
products such as hand-held wireless telephones. Currently, the
World Health Organization is working to provide a framework for
international harmonization of RF safety standards.
The NCRP, IEEE, and ICNIRP all have identified a whole-body Specific
Absorption Rate (SAR) value of 4 watts per kilogram (4 W/kg) as a
threshold level of exposure at which harmful biological effects may
occur. Exposure guidelines in terms of field strength, power density
and localized SAR were then derived from this threshold value. In
addition, the NCRP, IEEE, and ICNIRP guidelines vary depending on
the frequency of the RF exposure. This is due to the finding that
whole-body human absorption of RF energy varies with the
frequency of the RF signal. The most restrictive limits on whole-body
exposure are in the frequency range of 30-300 MHz where the human
body absorbs RF energy most efficiently. For products that only
expose part of the body, such as wireless phones, exposure limits in
terms of SAR only are specified.
The exposure limits used by the FCC are expressed in terms of SAR,
electric and magnetic field strength, and power density for
transmitters operating at frequencies from 300 kHz to 100 GHz. The
specific values can be found in two FCC bulletins, OET Bulletins 56
and 65:
http://www.fcc.gov/oet/info/documents/bulletins/#56;
http://www.fcc.gov/oet/info/documents/bulletins/#65
6. Why has the FCC adopted guidelines for RF exposure?
The FCC authorizes and licenses products, transmitters, and facilities
that generate RF and microwave radiation. It has jurisdiction over all
transmitting services in the U.S. except those specifically operated by
the Federal Government. While the FCC does not have the expertise
to determine radiation exposure guidelines on its own, it does have
the expertise and authority to recognize and adopt technically sound
standards promulgated by other expert agencies and organizations,
and has done so . (Our joint efforts with the FDA in developing this
website is illustrative of the kind of inter-agency efforts and
consultation we engage in regarding this health and safety issue.)
Section 4: Safety Guidelines and Warranty Information
4A: Safety 124