What level of radiation at the frequencies used by the cellular network(1-2 Ghz) is harmful for human health?
Addition to the previous answer
First you need to understand how radiation causes cellular damage.
EM waves like γ-rays, X-rays and high-energy UV (in certain molecules even visible light) can knock out the electrons from the atom and create an ion and free radicals by breaking chemical bonds. This term — ionizing radiation is not used for low energy UV and visible light because these waves can only ionize a few types of molecules and are not ionizing in general. Moreover X-rays and γ-rays can dislodge even inner electrons which UV and visible light cannot (High energy γ-rays can also lead to the nuclear reaction of pair production). These ions that are formed are reactive and can attack other molecules (DNA/proteins etc) around them. DNA absorbs UV and this can cause DNA lesions such as dimerization of adjacent pyrimidines (via a cyclobutane bridge). Both reactive ions and pyrimidine dimers can cause cancer; the former is most frequent in melanomas which happen because of solar UV. Since UV cannot penetrate very deep, they affect mostly the skin (See here).
IR, with energy lower than visible light does not have sufficient energy to cause electronic transitions. But it can cause vibrational transitions such as bond stretching and bending. Microwaves have even lower energy and can only cause molecular rotation. Both IR and microwaves because of their property to make molecules move, generate heat.
Continuous usage of mobile phones can cause discomfort but only because of their heating effect. They can by no means cause cancer and even though mobile phone radiation is classified as a potential carcinogen (IARC Group 2B) perhaps because of the pressing allegations of certain factions, they do not have sufficient energy to cause DNA damage.
If you ask me if mobile phone radiation can be harmful to human health, then I would say yes, they can be potentially harmful with prolonged usage but in no way as harmful as to be causing cancer. I would say that it is as harmful as wine :P
Afaik. radio waves don't have enough energy to cause anything similar to the damage ionizing radiation (gamma rays) does.
What it can cause is probably heat damage similar to microwave ovens.
According to the United States Food and Drug Administration's Center for Devices and Radiological Health, a U.S. Federal Standard limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts of microwave radiation per square centimeter at approximately 5 cm (2 in) from the surface of the oven. This is far below the exposure level currently considered to be harmful to human health.
- Advanced Measurements of Microwave Oven Leakage - http://www.arpansa.gov.au/pubs/emr/microwave.pdf
According to the article referenced by wikipedia a 35 W/kg SAR level (caused by a 30 mW/cm2 leakage) can raise the tissue temperature with 1.5°C, which probably does not any serious damage. I guess from this you can count the radiation intensities - you are interested in - to any frequencies.