== Answer == Numerous studies have been done, including those by the federal government. The general conclusions are that no types of cancers or cell changed have been detected under cellphone usage against one's head. Of course, time well tell in reference to your question, as scientific studies are just that; science. Even if a low percentage of people did get cancer from cellphones, I would presume it wouldn't happen until late in life, when you'd most likely die of something else anyway. So keep utilizing those night and weekend minutes without any fears! And as far as health problems; there are people who claim they are "EMF Sensitive", so presumably most of these people will claim it affects their health. However, these people would be better off seeing a psychiatrist to ward of the nausea and sickness they (irrelevantly & factitiously) encounter from exposure to less than 1 watt of transmit power.
== Answer ==
No, but if your ringtone is too loud, you could lose your hearing. SO BE CAREFUL!!!!
== Another answer... ===
The affects on human health have been under constant debate for many years, specifically if the radiation emitted is enough to be damaging to the brain. It has been proven that depending on how close the cell phone antenna is to your head, between 20% and 60% of the radiation emitted by your cell phone is transferred into your head. The radiation actually penetrates the area around your head and is absorbed, with some radiation reaching an inch, to an inch and a half, into your brain.
Dr. George Carlo, PhD, JD, is an epidemiologist and medical scientist who, from 1993 to 1999, headed the first telecommunications industry-backed studies into the dangers of cell phone use. He ran afoul of the very industry that hired him when his work revealed preventable health hazards associated with cell phone use. His studies concluded that cell phone radiation caused DNA damage, impaired DNA repair, and interfered with cardiac pacemakers. European research later confirmed Dr. Carlo's findings.
European studies suggest that cell phone radiation contributes to brain dysfunction, tumors, and potentially to conditions such as autism, attention deficit disorder, neurodegenerative disease, and behavioral and psychological problems. Until further research into cellphone radiation is done or accepted, it is generally recommended that you use a headset at all times in order to maximize the distance between your head and the cellphone.
At the time of this writing (2012 Feb) there is no concrete evidence that cell phone usage has any immediate or long term physiological health effects at all. While radiation emmissions have, in the past, been a point of contention, there is no acceptable evidence published at this time indicating cell phones present a health hazard.
A note on Dr. George Carlo. Carlo worked with Dow Chemical, promoting the idea that dioxins were harmless (we now accept dioxins as a carcinogen). Carlo's CV also shows pro-smoking input, and a Congressional inquiry as to methods, with the optimum quote being, "Carlo seems to have spent $17.5 of the geverment's money without even getting a test tube wet."
First promoting the safety of cell phones, after his federally funded "study" completed, he did an immediate about-face and started promoting the damgers of cell phones, including a book on the topic. Now, it's indicated that Carlo has started a training center that teaches how to develop an income from the cell phone companies via tort style litigation.
Input from Dr. George Carlo is often questions and appears to be suspect. Consider a more objective, less well-funced source for information.