16Is all this radio safe? What the agencies say

The short version: Governments cap radio-frequency (RF) exposure with limits designed to prevent tissue heating, with safety margins built in. The US uses FCC limits dating to 1996; an international commission, ICNIRP, publishes guidelines that were updated in 2020 to cover 5G. In 2011 the WHO's cancer agency, IARC, classified RF fields as "possibly carcinogenic" (Group 2B) on limited evidence, and a WHO-commissioned review published in 2024 found moderate-certainty evidence that mobile phone use likely does not raise the risk of brain and other head tumors, a finding some critics dispute. This section reports what each body says, with attribution, and does not offer advice.

What does "radiation" mean here?

What you see: A phone's legal screen listing a "SAR" figure, or a sticker on a cell site warning about RF exposure.

Radio waves, Wi-Fi, cell signals and microwaves are non-ionizing radiation: they do not carry enough energy per photon to knock electrons off atoms, which is what X-rays and nuclear radiation do. The question agencies study is what lower-energy RF does to the body.

The World Health Organization's answer on the known mechanism: "Tissue heating is the main mechanism of interaction between radiofrequency fields and the human body," and current exposure levels cause a negligible temperature rise.²⁷⁸ Exposure limits are built around that mechanism.

The key unit is SAR (specific absorption rate): how much RF energy body tissue absorbs, measured in watts per kilogram (W/kg).

What is the SAR limit for cell phones in the US?

What you see: "SAR: 1.19 W/kg" or similar in a phone's settings or manual.

The FCC's limits for the general public are in 47 CFR 1.1310. For 100 kHz to 6 GHz they are:²⁷⁹

For far-field exposure, the same rule sets a general-population power-density limit of 1.0 mW/cm2 from 1,500 to 100,000 MHz.²⁷⁹

These limits have a history. The FCC adopted exposure limits based on recommendations from the National Council on Radiation Protection and Measurements (NCRP) on August 1, 1996, covering 300 kHz to 100 GHz. Device SAR limits took effect August 7, 1996, and all licensees had to comply by September 1, 2000.²⁸⁰ The FCC's technical guide for testing compliance is OET Bulletin 65, "Evaluating Compliance With FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields."²⁸⁰

The FCC's RF safety page says it "is confident in its RF exposure guidelines," and that in 2019 it concluded the best available scientific evidence supports maintaining the existing limits.²⁸¹

In the US, the FDA shares regulatory responsibility for cell phones with the FCC: the FCC sets the emission limits and the FDA provides scientific input.²⁸² The FCC describes the FDA as the agency with "primary jurisdiction for investigating mobile phone safety."²⁸³ In 2019, Jeffrey Shuren, director of the FDA's Center for Devices and Radiological Health, wrote to the FCC that "the existing safety limits for cell phones remain acceptable for protecting the public health."²⁸⁴ The FCC adopted its decision to keep its limits (FCC 19-126, ET Docket 19-226) on November 27, 2019, and released it on December 4, 2019.²⁸⁵²⁸⁶

What are the ICNIRP guidelines?

What you see: A European or UK phone spec sheet quoting a SAR figure "over 10 g," or a council report citing "ICNIRP compliance" for a new mast.

ICNIRP, the International Commission on Non-Ionizing Radiation Protection, publishes the exposure guidelines used by many countries. Its current RF guidelines, covering 100 kHz to 300 GHz, were published in March 2020 in the journal Health Physics. They replace the 1998 RF guidelines and, in ICNIRP's words, "cover many applications such as 5G technologies, WiFi, Bluetooth, mobile phones, and base stations."²⁸⁷

The general-public basic restrictions in the 2020 guidelines are:²⁸⁸

For the general public, ICNIRP applies a reduction factor of 50 for whole-body exposure and 10 for local limits; these are its safety margins.²⁸⁸ Above 6 GHz, energy is absorbed close to the skin surface, which is why the guidelines switch from SAR to a power-density measure.

Why is the US limit 1.6 and Europe's 2.0?

What you see: Two different SAR numbers for the same phone model in different countries.

The two figures are measured differently. The FCC averages over 1 gram of tissue;²⁷⁹ ICNIRP averages over 10 grams.²⁸⁸ Averaging over a smaller mass captures sharper hot spots, so a 1 g number and a 10 g number for the same phone are not directly comparable, and "1.6 is stricter than 2.0" is not a fair reading on its own. The whole-body limit, 0.08 W/kg, is the same in both.²⁷⁹²⁸⁸

Canada's limits are set in Health Canada's Safety Code 6 (2015). For the general public they are 0.08 W/kg whole-body, 1.6 W/kg over any 1 g for the head, neck and trunk, and 4 W/kg over 10 g for limbs, averaged over 6 minutes, so Canada uses the same 1 g measure as the US.²⁸⁹

Switzerland applies a precautionary principle under which, according to its Federal Office of Communications, radiation limits "must be ten times lower in Switzerland than in neighbouring countries."²⁹⁰ Italy long used a 6 V/m attention value and quality objective for RF fields; according to the Molise regional environmental agency (ARPA Molise), Law 214 of December 30, 2023 raised both to 15 V/m, fully in effect from April 2024.²⁹¹

What does "possibly carcinogenic" (Group 2B) mean?

What you see: A headline saying "WHO: cell phones may cause cancer."

On May 31, 2011, in Lyon, a working group of 31 scientists from 14 countries convened by the International Agency for Research on Cancer (IARC), part of the WHO, classified RF electromagnetic fields as Group 2B, "possibly carcinogenic to humans."²⁹²

According to IARC's press release:²⁹²

• The basis was "limited" evidence for glioma (a brain tumor) and acoustic neuroma (a tumor of the hearing nerve) in wireless phone users, and "inadequate" evidence for other cancers.
• One study of past cell phone use (up to 2004) found a 40% increased glioma risk in the highest category of heavy users, who reported an average of 30 minutes a day over 10 years.
• Working group chair Jonathan Samet said: "The conclusion means that there could be some risk."
• IARC adds that the words "probably" and "possibly" carcinogenic "have no quantitative significance."

That last point matters for reading headlines. IARC's groups describe how strong the evidence is that something can cause cancer, not how large any risk is.

Australia's radiation agency, ARPANSA, describes the IARC classification as "largely based on limited evidence from human observational studies," and dates it to 2013,²⁹³ the year the full monograph was published, while IARC's own press release dates the decision to May 2011.²⁹² Both dates appear in coverage; they refer to the meeting and the publication.

In 2024, an IARC Advisory Group recommended, in a summary published in The Lancet Oncology, that RF fields be re-evaluated "with high priority" in the latter half of 2025-2029.²⁹⁴ IARC's announcement of its next listed meeting, Volume 144 on lead and cadmium compounds (October 19-26, 2027), does not mention RF,²⁹⁵ and Microwave News reported in 2024 that no date for an RF review had been set.²⁹⁶

What did the 2024 WHO review find about phones and brain cancer?

What you see: A 2024 headline saying "WHO review finds no link between mobile phones and brain cancer."

WHO surveyed experts in 2018 to set research priorities and then commissioned a series of systematic reviews (studies that gather and grade all the relevant research on a question by a preset method).²⁹⁷ The cancer review in humans was led by Ken Karipidis of ARPANSA and published in Environment International in 2024:

Karipidis K, Baaken D, Loney T, Blettner M, Brzozek C, Elwood M, Narh C, Orsini N, Röösli M, Paulo MS, Lagorio S. "The effect of exposure to radiofrequency fields on cancer risk in the general and working population: A systematic review of human observational studies - Part I: Most researched outcomes." Environment International 2024; 191:108983.²⁹⁷

What it reported:²⁹⁷

ARPANSA, announcing the review on September 4, 2024, said more than 5,000 studies from 1994-2022 were screened and 63 were included, and that there has been "no rise in the incidence of brain cancers" despite greatly increased wireless use.²⁹³ ARPANSA's summary: "we can be more confident that exposure to radio waves from wireless technology is not a human health hazard."²⁹³ It also said WHO is preparing an Environmental Health Criteria monograph that will draw on this and the other commissioned reviews.²⁹³

The review has critics. Microwave News, a newsletter on non-ionizing radiation, wrote in September 2024 that "the results of this review were never in doubt," pointing to the authors' ties to ICNIRP, the inclusion of a Danish cohort study not designed to study cell phones, and the omission of rodent studies by the US National Toxicology Program and the Ramazzini Institute.²⁹⁸ The same article quotes the International Commission on the Biological Effects of Electromagnetic Fields (ICBE-EMF): "There is no scientific justification for concluding there is any certainty that RF exposures do not cause cancer."²⁹⁸

In a January 2025 reply in Environment International to a critical letter by Di Ciaula and colleagues, the review's authors said the review covered only human studies and that a separate review of animal studies was in progress.²⁹⁹

As of October 2026, WHO's radiofrequency page still describes the Environmental Health Criteria monograph as work under way, a health risk assessment "to be published as a monograph," with no publication date given.³⁰⁰

Is 5G dangerous to health?

What you see: A flyer or post linking 5G masts to illness, or the 2020 claims linking 5G to COVID-19.

The WHO's Q&A on 5G, dated February 27, 2020, says:²⁷⁸

• "No adverse health effect has been causally linked with exposure to wireless technologies."
• 5G at around 3.5 GHz produces exposure "similar to that from existing mobile phone base stations."
• Beam-forming, where 5G antennas steer energy toward users, may make exposure more variable, and this is still being studied.
• "Only a few studies" have examined the frequencies 5G uses, so conclusions draw on research across the wider spectrum.

ICNIRP states that its 2020 guidelines explicitly cover 5G.²⁸⁷ The WHO Q&A predates the 2024 review described above. How 5G networks are built is covered in cellular.

Some local governments and campaign groups have called for 5G moratoriums; this section quotes only national and international agencies. For what the boxes on poles and lampposts are, see the sister guide Street Code: utility poles.

In Boston

RF exposure limits in the US are set federally by the FCC, and the limits above are the ones that apply to devices and transmitters in Boston.²⁷⁹

Federal law also limits what states and cities can do. Under 47 USC 332(c)(7)(B)(iv), no state or local government may regulate the placement, construction or modification of personal wireless service facilities "on the basis of the environmental effects of radio frequency emissions," as long as those facilities comply with the FCC's rules.³⁰¹ For where the area's large transmitters stand, see towers.

Elsewhere in the world

ICNIRP's guidelines are international and explicitly cover phones, Wi-Fi, Bluetooth, base stations and 5G;²⁸⁷ the US instead sets its own limits through the FCC.²⁷⁹ The practical difference most people meet is the SAR figure on a phone: 1.6 W/kg over 1 g under US rules, 2 W/kg over 10 g under ICNIRP. IARC's 2011 classification is a single global finding, while national agencies differ in how they explain it to the public, as ARPANSA's framing above shows.²⁹³

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