I came across a video clip that claims to show the effects of cell phone usage on blood cells. Before taking the first blood sample and putting it under a HC-4000 live microscope the test person hadn't used a cell phone for 24 hours, other blood samples were taken after 6, 17 and 29 minutes of nonstop cell phone calling without using a headset. According to the clip, after 17 minutes of calling the blood can be compared with someone who suffers from a severe flu fever.
While it's not a very scientific study, it may be a wise idea to use a headset if you use your cell phone a lot.
