When I was in academia, I was involved in experiments consisting in the exposure of flies (drosophila melanogaster) to 900 MHz controlled electromagnetic fields

When I was in academia, I was involved in experiments consisting in the exposure of flies (drosophila melanogaster) to 900 MHz controlled electromagnetic fields. I participated to the design of the exposure chamber, essentially a bi-planar transmission line, with a peak electric field near 220 V/m. We were able to find evidence of an effect only after 7 days of continuous exposure to the field. The effect was an up-regulation of the genes encoding for a stress-response protein (Hsp70, aka heat-shock protein). We tried also exposure to pulsed high intensity magnetic field (~1T for 2 usec) for 3 hours, 1 pulse per second. Same effect. My opinion is that, as long as fields are at low intensity and for short periods, we can consider such exposures as moderately safe