Resolution of Notice of Inquiry and Maintenance of Existing Limits
In a comprehensive decision adopted on November 27, 2019, and released on December 4, 2019 (FCC 19-126), the Federal Communications Commission resolved and terminated its Notice of Inquiry in ET Docket No. 13-84 regarding human exposure to radiofrequency (RF) electromagnetic fields. After reviewing an extensive public record of over 1,000 comments and ex parte submissions, the Commission declined to propose amendments to its existing RF exposure limits.
The Commission determined that the existing safety limits reflect the best available scientific information, supported by expert federal health and safety agencies including the Food and Drug Administration (FDA) and the U.S. Environmental Protection Agency (EPA). Specifically, the FDA advised the FCC that the weight of scientific evidence has not linked cell phones with adverse health effects in humans and that current safety standards remain acceptable for protecting public health.
The Commission also reaffirmed its localized Specific Absorption Rate (SAR) evaluation procedures for consumer portable devices, declining to alter testing separation distances or mandate zero-spacing compliance testing. It noted that current procedures already test devices under extreme conditions at maximum power and incorporate conservative safety margins.
- Terminated ET Docket No. 13-84 and ET Docket No. 03-137.
- Maintained existing localized SAR limit of 1.6 W/kg averaged over 1 gram of tissue for consumer devices below 6 GHz.
- Affirmed the use of the SAM phantom and IEEE Std 1528-2003 testing standard as protective of both adults and children.
- Dismissed and denied a petition for reconsideration by the American Association for Justice (AAJ) regarding the classification of the pinnae (outer ears) as extremities.
Second Report and Order: Modernizing RF Evaluation Exemptions
In the Second Report and Order portion of the item, the FCC replaced its historical patchwork of service-specific categorical exclusions with a uniform, service-agnostic exemption framework based directly on physical principles: transmitter power, operating frequency, and separation distance from human presence.
Under the revised 47 CFR Section 1.1307(b), any applicant or licensee seeking an exemption from routine RF environmental evaluation must meet one of three broad classes of criteria for single RF sources:
For locations or devices with multiple RF sources operating in the same time-averaging period, the Commission established a single normalized summation formula combining SAR-based, MPE-based, and previously evaluated contributions to ensure cumulative exposure does not exceed 100 percent of the allowable threshold.
- 1-mW Blanket Exemption: Available maximum time-averaged matched conducted power does not exceed 1 mW across 100 kHz to 100 GHz, regardless of separation distance (including medical implants).
- SAR-Based Exemption: Applied between 300 MHz and 6 GHz for separation distances between 0.5 cm and 40 cm using a specific mathematical formula (Pth) scaled by frequency and distance.
- MPE-Based Exemption: Applied from 300 kHz to 100 GHz for separation distances of at least lambda/(2*pi), referencing defined ERP thresholds in Table 1.
- Multiple Source Summations: Requires normalized summation across all co-located transmitters and pre-existing field levels to remain less than or equal to 1.0.
Environmental Evaluation Methods and Mitigation Measures
For RF sources where an exemption cannot be claimed, the Commission clarified routine evaluation procedures. It removed specific references to Finite Difference Time Domain (FDTD) computational modeling in favor of allowing any validated numerical or computational method conforming to accepted standards. It also eliminated the 5-centimeter minimum evaluation distance requirement for portable devices operating above 6 GHz to reflect modern close-to-body use cases.
The Commission adopted standardized post-evaluation mitigation rules for fixed transmitter sites, defining four specific exposure categories to govern RF safety plans, access control, and warning signage. Licensees are granted a two-year transition period from the effective date of the rules to perform necessary re-evaluations and implement compliance mitigation.
- Category One (INFORMATION / Green): Continuous exposure is within the general population/uncontrolled limit; signs are optional.
- Category Two (NOTICE / Blue): General population limit is exceeded but within occupational limit; requires blue 'NOTICE' signs, positive access controls, and trained supervision for transient individuals.
- Category Three (CAUTION / Yellow): Occupational limit is exceeded by up to a factor of ten; requires yellow 'CAUTION' signs, physical/indicative barriers, and 6-minute time averaging or personal protective equipment.
- Category Four (WARNING / Orange or DANGER / Red): Exposure exceeds ten times the occupational limit or poses immediate contact injury/burn risks; access is prohibited without power reduction, or lockout/tagout procedures under 29 CFR Section 1910.147 must be executed.
- Signage Specifications: Must include the signal word, RF advisory symbol, source description, necessary protective behavior, and up-to-date monitored contact information readable from at least 5 feet (1.52 m).
Notice of Proposed Rulemaking for Future Technologies
In the companion Notice of Proposed Rulemaking (ET Docket No. 19-226), the Commission initiated proposals to address emerging wireless technologies, higher frequencies, and wireless charging applications.
The FCC proposed to extend the upper limit of its RF exposure rules from 100 GHz to 3,000 GHz (3 THz) and establish a localized power density limit above 6 GHz of 4 mW/cm2 averaged over 1 cm2 for the general population (20 mW/cm2 for occupational environments). The Commission also proposed limits on internal electric fields (Ei) between 3 kHz and 10 MHz to protect against electrostimulation effects, consistent with international guidelines.
Additionally, the NPRM seeks to incorporate 'device-based time-averaging' into the rules to permit portable devices to dynamically manage transmission power in real time over designated maximum time windows, and proposed requiring equipment certification for all Part 18 Wireless Power Transfer (WPT) devices.
- Proposed extending MPE frequency ceiling to 3 THz.
- Proposed localized power density limit of 4 mW/cm2 over 1 cm2 above 6 GHz.
- Proposed internal electric field limits (135*f V/m general public, 270*f V/m occupational) from 3 kHz to 10 MHz.
- Proposed sliding maximum averaging windows for dynamic device-based time-averaging (from 100 seconds below 2.9 GHz down to 1 second above 95 GHz).
- Proposed Part 18 definition and mandatory equipment certification for WPT devices.