The Effect of Microwave Irradiation on the Turnover Rate of Serotonin and Norepinephrine in Rat Brain
Solomon H. Snyder, M.D. · 1970
At a Glance
Of the 874 peer-reviewed studies in this collection on electromagnetic fields, 701 — 80.2% — reported biological effects. On children's brains specifically the direct evidence is thin and the honest summary is layered: tissue measurements show absorption properties change with age, animal work shows radiofrequency exposure producing DNA strand breaks in brain cells, one large birth cohort links prenatal phone exposure to behavioral difficulties while cautioning the link may be non-causal, and the largest brain-tumor study found no overall increase in risk.
Based on analysis of 903 peer-reviewed studies
Children's brains are fundamentally different from adult brains—not just smaller, but actively developing, forming new neural connections, and undergoing critical periods of growth. This raises important questions about how electromagnetic field exposure might affect the developing brain.
Researchers have approached this question through multiple methods: measuring how much RF energy children's brains absorb compared to adults, studying cognitive outcomes in children with various EMF exposures, and examining brain tissue effects in laboratory settings.
This page presents the scientific evidence on EMF exposure and childhood brain development.
Key Findings
- -701 of 874 studies (80.2%) in this collection found biological effects from electromagnetic field exposure
- -Radiofrequency exposure produced single- and double-strand DNA breaks in rat brain cells at a whole-body absorption rate of 1.2 W/kg, from both pulsed and continuous-wave radiation (Lai and Singh 1996)
- -Tissue dielectric properties decrease with age, most markedly in brain and skull, which is the measured basis for expecting different absorption in children (Peyman 2001)
- -Prenatal phone exposure was associated with emotional and hyperactivity problems at age seven across 13,159 children, an association the authors warn may be non-causal (Divan 2008)
- -The largest brain-tumor study found no overall increased risk — 2,708 glioma and 2,409 meningioma cases across 13 countries — with suggestions of elevated glioma risk at the highest exposures that bias prevents interpreting causally (INTERPHONE 2010)
What the Research Shows
What the Research Shows
Of the 874 peer-reviewed studies indexed here on electromagnetic fields, 701 — 80.2% — reported measurable biological effects. Very few examine children's brains directly. Children cannot be enrolled in controlled radiofrequency exposure experiments, so the evidence comes from animal brain tissue, tissue-property measurement, adult cognitive testing, and observational cohorts.
How Absorption Changes With Age
Peyman and colleagues (2001) measured the dielectric properties of ten rat tissues at six ages across 130 MHz to 10 GHz. Properties decreased with age, and the trend was most apparent in brain, skull and skin, driven by declining water content. Because those properties govern how radiofrequency energy enters and deposits in tissue, younger tissue interacts with these fields differently. This is the measured basis for treating children's exposure as a distinct question — tissue data from animals, not a measured dose to a child's brain.
What Exposure Does to Brain Cells
Lai and Singh (1996) exposed rats at a spatial-averaged power density of 2 mW/cm², producing a whole-body specific absorption rate of 1.2 W/kg, and measured DNA strand breaks in individual brain cells four hours after exposure. Both single- and double-strand breaks increased, with no significant difference between pulsed and continuous-wave radiation. The authors positioned it as support for earlier in vitro and in vivo work showing radiofrequency effects on DNA.
A developing brain is building the structure it will use for life, and DNA damage during that period carries different consequences than the same damage in a mature, slowly dividing tissue. That reasoning is why the animal result gets weighted heavily in discussions of children — it is an inference about vulnerability, not a measured pediatric outcome.
Cognition and Behavior
Preece and colleagues (1999) tested 36 adults under about 1 W mean power at 915 MHz in a randomized cross-over design. Only choice reaction time changed, and it improved. Word, number and picture recall and spatial memory were unaffected.
The behavioral signal in children comes from Divan and colleagues (2008), who followed 13,159 children in the Danish National Birth Cohort to age seven. Children with possible prenatal or postnatal phone exposure showed greater odds of behavioral problems — emotional and hyperactivity difficulties — with the prenatal association stronger and surviving adjustment for confounders. The authors state that the associations may be non-causal and may reflect unmeasured confounding.
Hutter and colleagues (2006) added population evidence in adults, finding effects on wellbeing and cognitive performance among 365 residents near base stations at exposures far below recommended limits, with no known mechanism at those levels.
The Strongest Counter-Evidence
The INTERPHONE study ran an interview-based case-control study across 13 countries with 2,708 glioma and 2,409 meningioma cases and matched controls. It found no overall increase in either tumor type among mobile phone users — in fact reduced odds ratios that its authors attributed to participation bias or other methodological limitations. Suggestions of increased glioma risk appeared at the highest exposure levels, but the authors concluded that bias and error prevent a causal interpretation. That study concerns adults and tumors, not children and development, and it is the most substantial null result in this area.
What This Does Not Establish
Nothing here demonstrates that phone or WiFi exposure impairs a child's brain development. The tissue and DNA work is animal-based at exposures above typical use. The cognitive findings are in adults and are not uniformly negative. The behavioral cohort measures recalled phone use and carries the confounding its authors name.
Reasonable Practice
The steps that follow from this evidence are the ones that would be sensible even if every study above were overturned: keep phones away from children's heads by using speaker mode or wired headphones, favor texting over calling, keep devices out of bedrooms overnight, and use wired connections where devices do not move. Each reduces exposure during the years when the tissue differences are largest, and none costs anything worth counting.
Related Studies (903)
NUCLEAR MAGNETIC RESONANCE EVIDENCE USING D2O FOR STRUCTURED WATER IN MUSCLE AND BRAIN
Freeman W. Cope · 1969
THE ROLE OF DIFFERENT BRAIN FORMATIONS IN EEG REACTIONS OF RABBITS TO A CONSTANT MAGNETIC FIELD AND ELECTROMAGNETIC FIELDS OF ULTRA HIGH AND SUPERHIGH FREQUENCIES
R. A. CHIZHENKOVA · 1967
Researchers exposed rabbits for one minute to a constant magnetic field of 460 versts, a UHF field of wavelength 7.5 z at 30 v/m, and an SHF field of wavelength 12.5 cm with power flux density 40 m W/cm?. The constant magnetic field increased the number of EEG spindles. UHF and SHF fields caused the appearance of slow high-amplitude waves, which could be accompanied by increased spindles. Unilateral ablation of the midbrain reticular formation, posterior atrolateral thalamic nucleus, or anterior hypothalamus did not hinder these EEG responses. The authors concluded that the fields act directly on the central nervous system, not reflexively.
METHOD FOR THE MEASUREMENT OF IMPEDANCE CHANGES IN BRAIN TISSUE
R. T. KADO, W. R. ADEY, M.D. · 1965
SOME CLINICAL MANIFESTATIONS DUE TO CHRONIC ACTION OF THE CENTIMETER RANGE WAVES
E. A. Drozichina et al. · 1962
The researchers reviewed literature data and clinical observations from the Institute of Industrial Hygiene and Occupational Diseases of the USSR Academy of Medical Sciences collected over many years. They found that electromagnetic fields from centimeter-range waves under industrial conditions produced functionally reversible changes in organs and systems. In some cases these functional disturbances progressed to more pronounced and persistent pathological states characterized by vascular pathology and deviations in brain bioelectric activity.
ELECTROMAGNETIC PHENOMENA WHICH RADIATE FROM THE HUMAN BRAIN DURING INTENSE PSYCHOSENSORIAL ACTIVITY FROM DREAMY, HALLUCINATORY AND TELEPSYCHIC STATES
Cazzamalli, Ferdinando · 1960
THALAMO-CORTICAL SYSTEMS AND THE ELECTRICAL ACTIVITY OF THE BRAIN
JASPER, HH · 1948
LESIONS OF THE BRAIN FOLLOWING FEVER THERAPY
F. W. HARTMAN · 1937
THE BIOLOGICAL EFFECT OF SHORTWAVES ON THE BRAIN AND INVESTIGATION OF A THERAPY FOR CHRONIC BRAIN DISEASES
Paul J. Reiter · 1936
Cellular EffectsNo Effects Found
IN VITRO STUDY OF MICROWAVE EFFECTS ON CALCIUM EFFLUX IN RAT BRAIN TISSUE
Unknown authors
Control samples were processed identically without microwave power applied. The authors concluded that low power density pulsed microwave energy does not significantly alter calcium efflux.
EFFECTS OF LOW POWER MICROWAVES ON THE LOCAL CEREBRAL BLOOD FLOW OF CONSCIOUS RATS
Unknown authors
Researchers measured local cerebral blood flow in multiple brain regions of conscious rats using a radioactive iodoantipyrine technique. Rats were exposed for 30 minutes to pulsed microwaves at 1 mW/cm² or 15 mW/cm² average power density, or sham exposure. Both exposure levels increased blood flow by 10 to 144 percent in 16 of 20 regions, with the largest significant increases in the pineal, hypothalamus, and temporal cortex at 1 mW/cm² and in the pineal, temporal cortex, inferior colliculus, and medial geniculate at 15 mW/cm².
MICROWAVE EFFECTS ON NATURALLY OCCURRING CELL MEMBRANE CONSTITUENTS: A RAMAN SPECTROSCOPIC STUDY OF BOVINE BRAIN SPHINGOMYELINS
Unknown authors
The liposomes undergo thermally induced phase transitions between 30 °C and 40 °C. Samples were exposed to continuous-wave 2.4 GHz microwave radiation at power levels up to 25 mW/cm² while held at 36 °C. An increase in bilayer fluidity appeared above a threshold of 10–15 mW/cm², and at ~20 mW/cm² the fluidity change matched a ~3 °C temperature shift while bulk temperature rose only ~1 °C. The authors concluded a steady-state temperature difference exists between the bilayer interior and the surrounding aqueous medium under these exposure conditions.
Differential Heating of the Cortex, Hypothalamus and Rectum in Three Species by 2450-MHz Microwaves
Unknown authors
Animals were irradiated at 30 to 40 mW/g until rectal temperature reached 42.5 to 43.0 °C, then temperatures were recorded for over three hours. At baseline, cortical and hypothalamic temperatures were significantly lower than rectal temperatures in all three species. After heating, cortical temperature fleetingly exceeded rectal temperature in all species, while hypothalamic temperature exceeded rectal temperature only in rabbits. Brain temperatures fell rapidly in the first minute after exposure while rectal temperature declined much more slowly.
MICROWAVE EFFECTS ON ENERGY LEVELS OF BRAIN AND MALIGNANT BRAIN TUMOR
Unknown authors
Brain & Nervous SystemNo Effects Found
DRUG STUDIES OF MWR EFFECTS ON THE BLOOD BRAIN BARRIER
Unknown authors
Researchers exposed rats to 1.3 GHz pulse-modulated microwave radiation for 3 hours daily over 2-3 weeks at SARs ranging from 0 to 2.6 mW/g. After exposure, they measured the time to loss of righting reflex following barbital injection and found no significant differences between exposed and control rats at SARs of 0.42, 0.96, and 2.6 mW/g. In a separate experiment, rats exposed at 2.6 mW/g for two weeks were injected with dopamine and tested on an open field; although defecation was more frequent in exposed rats, no significant differences in motor activity were observed.
Brain & Nervous SystemNo Effects Found
STUDIES ON MICROWAVE AND BLOOD-BRAIN BARRIER INTERACTIONS
Unknown authors
Evans blue dye was injected either intracarotidally or intravenously to detect barrier opening. Microwave exposure produced no Evans blue staining in the brain except in the pineal body, pituitary gland, and choroid plexus, which lack a barrier. One brain exposed to 5 mW/cm2 and another brain exposed to 40 mW/cm2 showed unilateral hemispherical staining in several brain regions after intracarotid dye injection.
EFFECTS OF RADIO FREQUENCY FIELDS ON THE EEG OF RABBIT BRAINS
Unknown authors
IS THE BLOOD-BRAIN BARRIER ALTERED BY RF IRRADIATION?
Unknown authors
LOCALIZED HYPERTHERMIA IN DOG BRAIN USING AN INVASIVE MICROWAVE PROBE
Unknown authors
Early Developmental Deficits in Rats Following In-utero Exposure to 500 μW/cm², 2450-MHz Microwaves
Unknown authors
Researchers exposed eight pregnant rats to 500 uW/cm² 2450 MHz microwaves for 20 hours a day during the first 19 days of gestation. Exposed litters had seven times more neonatal deaths than controls, and pups weighed less on day 7 and opened their eyes one day later. Prenatally exposed females showed accelerated growth between 40 and 60 days of age and maintained a 10% higher body weight into adulthood.
ELECTROMAGNETIC RADIATION EFFECTS ON THE BLOOD-BRAIN BARRIER SYSTEM OF RATS
Kenneth J. Oscar, T. Daryl Hawkins
Permeability increases were also seen for inulin but not for dextran, and the effect was present immediately and at 4 hours but not at 24 hours after exposure. The magnitude of permeability change depended on microwave modulation, with differences between pulsed and continuous-wave exposures at the same average power density and between different pulse characteristics.
ASSESSMENT OF THE BIOLOGICAL EFFECTS OF RADIOFREQUENCY RADIATION
Joseph M. Lary, David L. Conover, William E. Murray
The authors reviewed and critically evaluated the radiofrequency biological effects literature through 1982. The review indicated that there appears to be a threshold for adverse biological effects in animals at a specific absorption rate of about 2 W/kg. At SARs between 1.8 and 4.5 W/kg, adverse effects included death, temperature increases exceeding 3%, hemorrhagic lesions, staggering and spasms in chicks, and extreme agitation in dogs. At SARs below 1.8 W/kg no clearly adverse effects were reported, but measurable temperature increases and physiological changes occurred in the 0.17 to 1.8 W/kg range. At SARs below 0.17 W/kg no temperature increases were reported and most effects involved calcium efflux or blood-brain barrier permeability.
A SYSTEM FOR PRODUCING LOCALIZED HYPERTHERMIA IN BRAIN TUMORS THROUGH MAGNETIC INDUCTION HEATING OF FERROMAGNETIC IMPLANTS
Unknown authors
The researchers are developing a magnetic induction system to produce localized hyperthermia in intracranial tumors. Differential heating is achieved using small ferromagnetic seeds that can be stereotactically embedded in residual tumor during craniotomy. In phantom tests, Trial 16 showed a temperature differential greater than 4°C out to 1 cm from the implant site with no significant direct heating of the phantom by the RF field. Heating patterns in single seed phantoms matched the theoretically expected inverse radial distance dependence.
THE EFFECT OF PRENATAL MICROWAVE EXPOSURE ON THE DEVELOPMENT OF BEHAVIORAL RESPONSES IN THE MOUSE
Unknown authors
Pregnant ICR mice were exposed to 2450 MHz continuous-wave radiation for 3 hours daily from gestational day 7 to 17 at an average power density of 10 mW/cm². Pups were tested from day 1 to day 21 postpartum using a battery of behavioral and neurological tests, all conducted blind. Exposed pups showed delayed initiation of several behavioral responses compared with sham-exposed pups. The delay affected the time needed for all exposed pups to achieve each response, but all exposed pups eventually reached the same developmental level as controls.
THERMAL EFFECTS ON COLONIC AND REGIONAL BRAIN TEMPERATURE IN UNANESTHETIZED RATS EXPOSED TO 2450 MHz CW MICROWAVES
Unknown authors
Researchers monitored colonic temperature and temperatures in the cerebral cortex, hypothalamus, cerebellum, and medulla of unanesthetized rats that were either sham-exposed or exposed to 2450 MHz CW microwaves at 65 mW/cm² for 30 or 90 minutes. Regional brain and colonic temperatures were significantly higher in exposed rats than in sham controls after both exposure durations. In sham rats the mean cortical temperature was 36.6°C. After 30 minutes of exposure cortical temperature rose to 40.0°C and after 90 minutes to 42.1°C. Cortical and cerebellar temperatures were slightly lower than colonic temperature, while hypothalamic and medullary temperatures were slightly higher in all groups.
What This Means for You
- Children's developing brains may be more susceptible to EMF effects than adult brains.
- Limit screen time and device use, especially for younger children.
- Use speakerphone or wired headphones instead of holding phones to children's heads.
- Shield your child's phone with a radiation-deflecting pouch. SYB Phone Pouch
Further Reading:
Frequently Asked Questions
No study in this collection measured electromagnetic exposure against children's brain development directly. The supporting evidence is indirect: radiofrequency exposure produced DNA strand breaks in rat brain cells (Lai and Singh 1996), absorption-governing tissue properties differ with age (Peyman 2001), and prenatal phone exposure was associated with behavioral difficulties at age seven in a 13,159-child cohort whose authors caution the link may be non-causal (Divan 2008).
The physical basis is real but narrower than usually stated. Dielectric properties governing radiofrequency absorption decrease with age, most markedly in brain and skull tissue, because water content falls (Peyman 2001). That means young tissue interacts with these fields differently. Combined with a developing nervous system's smaller margin for error in repair, it is a reasonable basis for extra caution — not a measured multiplier for a child's absorbed dose.
No. The largest study of mobile phones and brain tumors, INTERPHONE, examined 2,708 glioma and 2,409 meningioma cases across 13 countries in adults and found no overall increase in risk, with suggestions at the highest exposure levels that its authors said bias and error prevent interpreting causally (INTERPHONE 2010). This collection contains no comparable pediatric tumor study.
Use the measures that reduce exposure at no cost: speaker mode or wired headphones instead of the phone at the ear, texting instead of calling where it makes no difference, devices out of bedrooms overnight, and wired connections for anything that stays put. These are worth doing on the strength of the evidence as it stands, and they remain sensible whichever way the science resolves.
Further Reading
For a comprehensive exploration of EMF health effects and practical protection strategies, explore these books by R Blank and Dr. Martin Blank.
