Could cell-phone radiation cause cancer? It is very crucial that I ask whether it could and not whether it does. I do not mean to be the least controversial.
To my surprise, having read "Physics for Future Presidents" by Richard Muller last year, I've come across a sentence of the sort (I'm paraphrasing):

cell phone radiation is way too weak to effect molecular structure, and therefore any claim about cell phone radiation causing cancer can be attributed to people blaming cell phones for their cancer.

This seems like a very strong statement! Is this a consensus among physicists that there is absolutely nothing to the claim that cell phone radiation could possibly (in any significant way) cause cancer? Is this really just being thrown around because people don't understand the physics?
To be very precise, the question is: is there a physics model that would suggest a mechanism by which cell phone radiation can cause any sort of damage that could lead to cancer?
 A: This wiki article  covers most bases.
In conclusion, the connection to cancer is unclear from controlled studies. There is some surface heat that can be generated when next to the head, of the order of 2 watts but not clear how bad that is. Sunbathing hatless heats by many more watts (1300/m^2). Cancer of the skin has been connected with the sun due to ultraviolet radiation ( cell phones are microwave range), but not the head.
If I were a man I would avoid hanging a cell phone next to the family jewels, because heat is deleterious to fertility:).
A: It could due to multi-photon effects. It's already known that cell phones cause changes to brain activity. This was widely reported in the news. For example see "Cell Phone Study: Cell Ups Brain Activity". As of now, this is an unknown effect. So it might be associated with something that causes cancer.
(I'm not worrying.)
A: No, cell phone use does not cause cancer. We know it doesn't cause cancer because:


*

*There is no plausible mechanism.

*Animal studies show no effect.

*Human studies that get non-null results don't show a dose-response.


Doing these cell-phone studies with human subjects makes as much sense as doing studies to figure out whether I can cause my neighbors to get cancer by thinking evil thoughts about them. In both cases, there is no remotely plausible physical mechanism for the direct effect as postulated. The only reason to do the cell-phone study and not to do the evil-thoughts study is that the former appeals deeply to people's folk beliefs, which have been built up from decades of movies and comic books where "radiation" causes magical effects.
Some studies with human subjects give positive results and some give null results. This should not surprise us. The studies are measuring the relative sizes of their random and systematic errors. In the studies where they succeed in getting their random errors down to a smaller level than their systematic errors, they will measure either a positive or a negative correlation with cancer. In the ones where they succeed in getting their systematic errors down to a smaller level than their random errors, they will get a null result.
A: Microwaves and radiowaves are non-ionising radiation; they simply do not have enough energy.
Radiation causes cancer by ionsing atoms close to DNA structure which damages the strands, leading to mutations.
Non-ionising radiation such as that from a cell phone cannot cause this type of damage.
A: Having co-authored a review of the epidemiologic research*, I believe long term (approx. 10 or more years) cell phone use increases tumor risk in humans, especially gliomas, acoustic neuromas, and tumors of the parotid gland.
I agree with mbq that the effect is likely due to electromagnetic radiation (EMR) that interferes with bioelectrical processes through non-thermal mechanisms. 
A cursory review (unpublished) of 116 published toxicology studies, including animal studies and human cellular studies, suggests that some cell phone carrier systems are more likely to be biologically reactive than others. Namely, systems that pulse the signal at extremely low frequencies (i.e., TDMA, GSM, and UMTS) are about three times more likely to yield statistically significant biologically reactive outcomes as compared to carriers that do not pulse the signal (i.e., CDMA and W-CDMA) (36% vs. 12%).  However, when EMR is tested at higher power outputs that exceed the current legal limits for cell phones (based upon a measure called the Specific Absorption Rate), then toxic effects are more likely observed regardless of carrier. However, at these higher power outputs we cannot rule out a thermal mechanism.


*

*Seung-Kwon Myung, Woong Ju, Diana D. McDonnell, Yeon Ji Lee, Gene Kazinets, Chih-Tao Cheng, and Joel M. Moskowitz. Mobile Phone Use and Risk of Tumors: A Meta-Analysis. Journal of Clinical Oncology. 20(27):5565-5572. Published online first Oct 13, 2009. Nov 20, 2009.URL: http://www.ncbi.nlm.nih.gov/pubmed/19826127
A: Generally ,I do not think cell phone use significantly increase the risk of getting cancer , However, I think that cell phone use have temporary effect on cognitive function because EMFs even if it is non-ionizing can have interactions with biological systems especially the brain which is electrically and metabolically very active .
