Study Spotlight: 5G at 700 MHz Shows No Biological Effects on Brain Cells in New French Study

Published March 28, 2026 in Scientific Reports (Nature portfolio) — PMID 41904248

The Big Picture

One of the most common concerns about 5G is whether these signals can harm brain tissue. A team from the University of Bordeaux and University of Limoges just published one of the most thorough studies to date testing 5G-modulated RF-EMF on brain cells — and found nothing.

No oxidative stress. No cell death. No growth changes. At exposure levels double the European safety limit.

Classification: ✅ Reassuring

What They Did

Puginier and colleagues at CNRS (France’s national research center) exposed two types of brain cells to 5G-modulated 700 MHz RF-EMF:

Primary rat cortical astrocytes — the support cells that make up about half of brain tissue, critical for brain health and neuron function
Human SH-SY5Y neuroblastoma cells — a widely-used human neuronal cell model for studying brain biology

Exposure Conditions

The study used transverse electromagnetic (TEM) cells — specialized chambers that deliver precise, uniform RF exposure with accurate dosimetry:

Parameter	Low Dose	High Dose
Frequency	700 MHz (5G band)	700 MHz (5G band)
Modulation	5G NR signal	5G NR signal
SAR	0.08 W/kg	4 W/kg
vs ICNIRP limit	4% of limit	200% of limit
Duration	1 hour and 24 hours	1 hour and 24 hours

The 700 MHz band is increasingly important — it’s one of the primary frequencies allocated for 4G and early 5G deployment globally, yet has been poorly studied compared to higher frequencies like 1800 or 2450 MHz.

What They Measured

Using multiparametric flow cytometry (a technique that simultaneously measures multiple cellular properties), they quantified:

Mitochondrial reactive oxygen species (ROS) — the oxidative stress markers most commonly cited in EMF health concerns
Cell viability — whether cells survived exposure
Apoptosis (programmed cell death) — measured as both early and late stages
Cell proliferation — whether astrocytes changed their growth rate

Cells were analyzed both immediately after exposure and after a 24-hour recovery period — capturing both acute and delayed effects.

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What They Found

The Bottom Line: Nothing

“Across all exposure conditions, no statistically significant differences were detected compared to sham controls.”

Every measurement, at every dose, at every time point, in both cell types: no effect.

Let’s break it down:

Oxidative Stress (ROS)

At 0.08 W/kg (1 hour): no change
At 0.08 W/kg (24 hours): no change
At 4 W/kg (1 hour): no change
At 4 W/kg (24 hours): no change
After 24-hour recovery from any exposure: no change

Cell Death (Apoptosis)

Early apoptosis: unchanged across all conditions
Late apoptosis: unchanged across all conditions
No dose-response trend whatsoever

Cell Viability

Astrocytes: fully viable at all doses
Neuronal cells: fully viable at all doses

Cell Proliferation

Astrocyte growth rate: unaffected

Were the Assays Working?

This is critical: positive controls with hydrogen peroxide (H₂O₂) successfully triggered significant ROS increases and apoptosis, confirming the measurement systems could detect real effects. The assays were sensitive — they simply had nothing to detect from the RF-EMF exposure.

Why This Study Matters

1. It Used a Real 5G Signal

Many previous studies used continuous wave (CW) signals that don’t reflect actual telecommunications exposure. This study used 5G NR-modulated signals — the actual waveform your phone transmits.

2. Isothermal Conditions Were Verified

Temperature is the critical confound in RF-EMF research. At 4 W/kg, heating effects can occur. The researchers confirmed isothermal conditions — meaning any effects would have been non-thermal, the mechanism at the center of the EMF health debate.

3. Two Complementary Brain Cell Models

Using both rat astrocytes (primary cells, not a cancer line) and human neuronal cells provides stronger evidence than either alone. Astrocytes are often overlooked in EMF research despite making up ~50% of brain cells.

4. The 700 MHz Gap

This is one of the first studies to specifically investigate 700 MHz 5G effects on brain cells. Previous reassuring studies focused on higher frequencies (3.5 GHz, 26 GHz). The 700 MHz band penetrates tissue more deeply than higher 5G bands, making it particularly relevant for brain exposure during phone calls.

5. High-Impact Journal

Scientific Reports (Nature portfolio) is a reputable, peer-reviewed journal. The French institutions involved — CNRS, Bordeaux INP, EPHE — are among Europe’s leading research centers.

How This Fits With Other Evidence

This study joins a growing body of controlled lab research finding no effects at or near safety limits:

Study	Frequency	Cell/Model	Finding
This study (Puginier 2026)	700 MHz 5G	Brain cells	No effects at 4 W/kg
Allocca 2026	1950 MHz LTE	Neuroblastoma	No effects at 1.25 W/kg
Michelant 2026 (INERIS)	26 GHz 5G	Human volunteers	No stress biomarker changes
Leclercq 2025 (same group)	3.5 GHz 5G	Skin fibroblasts	No oxidative stress at 4 W/kg
Chen & Zhang 2026	3.5 GHz 5G	Head simulation	Brain SAR 1.7% of limit

The pattern across these studies: at realistic exposure levels, and even well above them, controlled studies consistently find no acute biological effects in brain tissue.

The Caveats

No single study settles the question. Important limitations to acknowledge:

In Vitro ≠ In Vivo

Cells in a dish lack the blood-brain barrier, immune system, circulating hormones, and complex neural networks of a living brain. Effects that require intact brain circuitry wouldn’t show up here.

Acute ≠ Chronic

The longest exposure was 24 hours with a 24-hour recovery. Real-world phone use spans decades. Cumulative or epigenetic effects couldn’t be captured in this timeframe.

Single Frequency

700 MHz is just one 5G band. Real-world exposure involves simultaneous signals from multiple frequencies, multiple devices, and multiple sources. Combined exposures might behave differently.

Positive Studies Exist

Other cell studies have found effects — typically at different frequencies, longer durations, or using different biological endpoints. The Bektas 2026 study found testosterone-producing Leydig cells affected at 1800/2450 MHz. The Zhu 2026 study found synergistic DNA effects when RF was combined with chromium pollution. Context matters enormously.

The Non-Thermal Debate Continues

This study found no non-thermal effects, but it only measured a subset of possible biological responses. Calcium signaling, gene expression, epigenetic changes, and immune modulation weren’t assessed.

What This Means for You

If you’re concerned about 5G:

This adds to the evidence that 5G signals at 700 MHz — even at double the safety limit — don’t cause acute damage to brain cells. Your actual exposure from a 5G phone is typically 50-100× below the levels tested here.

If you want to be cautious anyway:

Distance works. Using speakerphone or wired earbuds reduces brain exposure by 90%+ regardless of which frequency band your phone uses.

For the broader picture:

This is exactly the kind of study that builds the evidence base safety regulators rely on. Each new frequency, modulation type, and cell model tested fills a gap. The 700 MHz 5G gap just got significantly smaller.

Study Details

Title: “Biological effects of 5G-modulated 700 MHz RF-EMF exposure on neuronal and glial cell models under isothermal conditions”
Authors: Puginier E, Leclercq L, Poulletier de Gannes F, Hurtier A, Orlacchio R, Nabos P, Tijou H, Lévêque P, Arnaud-Cormos D, Percherancier Y, Lagroye I
Journal: Scientific Reports (Nature), March 28, 2026
DOI: 10.1038/s41598-026-43960-4
PMID: 41904248
Institutions: CNRS/University of Bordeaux, XLIM/University of Limoges, Institut Universitaire de France
Funding: Not specified in abstract
Conflicts of Interest: None declared

Frequently Asked Questions

Does this prove 5G is safe?

No single study proves safety — that requires decades of evidence across many frequencies, exposure levels, and health outcomes. But this study found no effects at twice the safety limit using rigorous methodology, which is genuinely reassuring for the 700 MHz band specifically.

Why test brain cells specifically?

Because the brain is closest to the phone during calls, and neurological concerns (headaches, cognitive effects, brain tumors) are among the most-cited potential health effects.

How does 700 MHz compare to other 5G frequencies?

700 MHz is a “low-band” 5G frequency that penetrates deeper into tissue compared to mid-band (3.5 GHz) or high-band (26+ GHz). It’s used for broader coverage, especially in rural areas. Deeper penetration means more tissue interaction — making safety data for this band particularly important.

What about long-term effects?

This study only tested acute exposures up to 24 hours. Long-term and chronic effects would require animal studies with lifetime exposure or large-scale epidemiological studies tracking human health over decades.

Were the researchers independent?

The study came from CNRS (France’s National Centre for Scientific Research) and public French universities. No industry funding was declared, and no conflicts of interest were reported. The lead institution (IMS-Bordeaux) has published both positive and null EMF findings in the past.

What should I do based on this study?

If you were specifically worried about 5G at 700 MHz harming your brain, this provides meaningful reassurance. For general precaution, using speakerphone or earbuds during calls remains the simplest way to reduce brain exposure from any phone signal.

Want to see what wireless infrastructure is near you? Search your address on EMF Radar to find cell towers, power lines, and substations in your area.

Read more from our Study Spotlight series: Is EMF Bad for You? | 5G Myths Debunked | EMF and Your Nervous System

Study: 5G at 700 MHz Shows No Biological Effects on Brain…