We investigated the mechanisms by which radiofrequency (RF) fields exert their 
activity, and the changes in both cell proliferation and the gene expression 
profile in the human cell lines, A172 (glioblastoma), H4 (neuroglioma), and 
IMR-90 (fibroblasts from normal fetal lung) following exposure to 2.1425 GHz 
continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) RF 
fields at three field levels. During the incubation phase, cells were exposed at 
the specific absorption rates (SARs) of 80, 250, or 800 mW/kg with both CW and 
W-CDMA RF fields for up to 96 h. Heat shock treatment was used as the positive 
control. No significant differences in cell growth or viability were observed 
between any test group exposed to W-CDMA or CW radiation and the sham-exposed 
negative controls. Using the Affymetrix Human Genome Array, only a very small (< 
1%) number of available genes (ca. 16,000 to 19,000) exhibited altered 
expression in each experiment. The results confirm that low-level exposure to 
2.1425 GHz CW and W-CDMA RF fields for up to 96 h did not act as an acute 
cytotoxicant in either cell proliferation or the gene expression profile. These 
results suggest that RF exposure up to the limit of whole-body average SAR 
levels as specified in the ICNIRP guidelines is unlikely to elicit a general 
stress response in the tested cell lines under these conditions.