Human Red Blood Cells Stay Stable After Wi-Fi-Band Electromagnetic Exposure

Human red blood cells exposed in vitro to 2.41 GHz electromagnetic fields at intensities typical of wireless communication devices showed no significant destabilization of their cell membranes, according to a study published in the journal BioRisk. The research, led by Bulgarian investigators, measured the release of hemoglobin from erythrocytes as a direct indicator of membrane integrity, and found that fields below the reference level for population exposure left the cells essentially unchanged, even after four hours of continuous irradiation.

The 2.4–2.5 GHz band is one of the most heavily used frequency ranges in modern communication technology, industry, and medicine. Wi-Fi routers, Bluetooth devices, Zigbee sensor networks, body area networks, and Internet of Things systems all operate in this microwave range, steadily raising ambient levels of high frequency electromagnetic fields. This has fueled public concern about possible deleterious effects on living organisms, particularly on children and adolescents, who are considered among the most sensitive groups because they will live with these technologies for the longest time.

Previous studies on microwave effects on biological systems have produced contradictory results, likely due to differences in irradiation conditions, the objects studied, and detection methods. Some experiments with human erythrocytes irradiated at 2.45 GHz found that short-term exposure in the reactive near-field of a wearable antenna had a stabilizing effect on the cell membrane, while longer exposure had a destabilizing one. Other work reported increased hemolysis in rats exposed daily for a month, along with elevated markers of lipid peroxidation and decreased antioxidant enzyme levels. Still other studies, including a multigeneration mouse experiment at 1966 MHz, found no harmful effects on fertility or development.

To resolve some of this ambiguity, the team designed two exposure setups in a semi-anechoic chamber. The first used an XBee S1 RF module connected to a microwave solid-state amplifier, transmitting a Zigbee-like pulsed signal at 2.41 GHz through a wearable textile polyester substrate antenna. Erythrocyte suspensions with a hematocrit of 40 percent were placed in the far-field region at 150 centimeters from the antenna, exposed to an electric field intensity of 0.213–0.238 V/m, comparable to power densities of 120–150 µW/m². The second setup employed a half-wave dipole metal antenna driven by a 50 W amplifier, generating a pulse-modulated signal with a pulse period of 4.608 ms and a pulse width of 2.304 ms. Samples were positioned at four distances corresponding to intensities of 5, 20, 40, and 180 V/m.

The blood material came from clinically healthy donors, with types A+ and A− investigated. Whole blood was centrifuged, the plasma and white blood cell coating removed, and the erythrocyte mass washed repeatedly with saline before being diluted to a hematocrit of 40 percent with phosphate buffer at pH 7.4. Treatment was applied between the fifth and twenty-fifth day after blood drawing, while samples were stored at 10 °C. Control cuvettes were shielded from electromagnetic fields in a metal box, background controls were placed in adjacent rooms, and some samples were incubated in water baths at 24, 32, or 38 °C for comparison with conventional heating.

Hemoglobin release was measured spectrophotometrically by recording absorbance at 413 nm, the maximum for hemoglobin, in the supernatant of each sample. The concentration of released hemoglobin was calculated using the molar extinction coefficient for hemoglobin at that wavelength. Results are presented as average values with standard errors from three to seven independent repetitions of each experimental variant.

After 20 minutes of exposure to the textile antenna signal, whether pulsed or continuous, no statistically significant difference in hemoglobin release was observed between treated and shielded control suspensions, even when measurements continued for five hours afterward. Notably, at three to four hours after the end of the pulsed exposure, a slight tendency toward membrane stabilization was noticed, echoing earlier findings with GSM 900 fields where released hemoglobin decreased over an hour after a 20-minute exposure. Even four-hour exposures at the same low intensity produced no significant membrane destabilization, with released hemoglobin reaching 18.54 µmol/l after four hours of continuous treatment, compared with 17.73 µmol/l four hours after a brief 20-minute exposure.

The picture changed only at the highest intensity tested. During four-hour exposure to 180 V/m continuous fields from the dipole antenna, significantly increased hemoglobin release appeared from the second hour onward and continued throughout the exposure. This intensity slightly exceeds the maximum allowed in controlled environments under the IEEE safety standard, which permits 174 V/m for workers in radio transmitters and base station installation, while the general population reference is 61.4 V/m. The other three positions, at 40, 20, and 5 V/m, resembled realistic population exposure scenarios and produced hemoglobin release similar to controls for the first three hours, with only slight elevations at 20 and 40 V/m after four hours.

Crucially, the samples exposed to 180 V/m showed a significant temperature increase to 32 °C, raising the question of whether the observed hemolysis was thermal in origin. Conventional heating experiments in water baths at 24, 32, and 38 °C produced released hemoglobin concentrations of 218±160, 311±235, and 277±209 µmol/l respectively, showing a tendency for heat-induced increase but with large standard errors that prevented a significant temperature-dependent differentiation. In a separate experiment, interrupting the 180 V/m exposure after one hour allowed the membrane to recover: released hemoglobin approached control levels within two hours of removing the field, though a slight elevation after one hour of irradiation had been detectable. The team notes that thermally induced hemolysis involves enzyme inactivation, formation of lytic agents, and melting of membrane lipids, but the temperatures examined fall below thresholds for spectrin alteration, enzyme inactivation, or lipid phase transition, suggesting oxidative processes between 20 and 37 °C may be essential in autohemolysis.

The authors conclude that in vitro exposure to 2.41 GHz electromagnetic fields emitted by wireless communication devices with power density below the reference level for general population exposure does not change the stability of the human erythrocyte cell membrane for up to four hours of exposure. They acknowledge that their results could not differentiate thermal from non-thermal effects at the highest intensity, and plan future experiments to determine whether non-thermal effects exist at permissible exposures and what mechanisms might underlie them. For the billions of people living alongside Wi-Fi and Bluetooth devices, the message is cautiously reassuring: at the intensities we actually encounter, our red blood cell membranes appear to hold firm.

Subject of Research: Biophysics

Article Title: Alterations in membrane stability after in vitro exposure of human erythrocytes to 2.41 GHz electromagnetic field

Article References: Angelova, B., Atanasova, G., Atanasov, N., Paunov, M., Gurmanova, M., & Kouzmanova, M. (2023). Alterations in membrane stability after in vitro exposure of human erythrocytes to 2.41 GHz electromagnetic field. BioRisk, 20, 83-96. https://doi.org/10.3897/biorisk.20.97616

Image Credits: AI Generated

DOI: 10.3897/biorisk.20.97616

Keywords: electromagnetic fields, erythrocytes, membrane stability, hemolysis, 2.41 GHz, wireless communication, BioRisk, Alterations, membrane, stability, vitro, exposure