Kumar G, Wood AW, Anderson V, McIntosh RL, Chen YY, McKenzie RJ. Evaluation of hematopoietic system effects after in vitro radiofrequency radiation exposure in rats. Int. J. Radiat. Biol.. Ahead of print. Nov, 2010.

Due to large increase in the use of mobile phones, public attention has been drawn to potential adverse effects of exposure to their radiofrequency (RF) electromagnetic fields (EMF). Although there have been many studies investigating possible RF EMF biological effects, there is still no clear evidence to indicate that this type of non-ionizing radiation poses a risk for human health.

The objective of this study was to investigate the effects of 900-MHz continuous wave radiofrequency radiation (RFR) exposure on the hematopoietic system in rats.

Rat femur and tibia bones were placed in Petri dishes containing media and divided into 900-MHz RF-exposed and sham-exposed groups. Dishes were kept in transverse electromagnetic cells for 30 minutes during the exposure period. The mean specific energy absorption rate (SAR) for the RF exposure was 2 W/kg at 16.7 W root mean square. After exposure, bone marrow cells were extracted and tested for proliferation rate of whole bone marrow cells and lymphocytes in a trypan blue exclusion test using a haemocytometer, maturation rate of erythrocytes by acridine orange (AO) staining, and DNA damage (strand breaks/alkali labile sites) of lymphocytes using an alkaline single cell gel electrophoresis assay (SCGE)/ Comet assay.

No significant differences in bone marrow cell or lymphocyte proliferation rates were observed between the RF-exposed and sham-exposed groups. The viability of attached bone marrow cells was observed to be 99.7% and the viability of attached lymphocyte cells was 99.8%. No significant differences in maturation rate of erythrocytes were observed between the RF-exposed and sham-exposed groups. Various parameters of DNA strand breaks and alkali labile sites were measured in the sham group and RF-exposed group. Comet length, comet height, comet mean intensity, head diameter, head mean intensity, % DNA in head, tail length, % DNA in tail, tail moment and olive moment were not significantly different between the sham- and RF-exposed groups.

Interpretation and Limitations
Numerous studies regarding RF radiation exposure have in general indicated no detectable damage to DNA, chromosome aberrations, or mutations in exposed bacteria, insects, or rodents. The authors suggest that this study confirms and strengthens the results of other studies since the hematopoietic system is the most proliferative system of the body, consisting of different types of stem cells, and is highly sensitive because hematopoietic cells undergo rapid division. The limitation of this study is that continuous wave exposure cannot be taken as fully representing mobile phone handset exposures because of the lack of pulse modulation. It is also difficult to extrapolate the results to humans.

This study suggests that a single RF exposure at the ICNIRP public SAR limit level of 2 W/kg at 900 MHz does not disrupt the cellular processes of blood cells in rat bone marrow.

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