Is there any health risk in cellular phones?

Question

Cellular phones are taking ever increasing part in our lives, and I keep hearing people saying they are harmful to our health.

Are there any scientific researches so far proving or disproving those claims?

I found couple of semi-scientific articles:

1. Is there any link between cellphones and cancer? which says:

   The possible connection between cellphones and cancer is controversial. Many years' worth of studies on cellphones and cancer have yielded conflicting results
   ...
   In one study that followed more than 420,000 cellphone users over a 20-year period, researchers found no evidence of a link between cellphones and brain tumors
   ...
   Another recent study suggested a possible increased risk of glioma — a specific type of brain tumor — for the heaviest cellphone users, but no increase in brain tumor risk overall.

2. Long-term Cell Phone Use Linked to Brain Tumor Risk which says:

   Long-term use of both mobile and cordless phones is associated with an increased risk for glioma, the most common type of brain tumor, the latest research on the subject concludes.
   The new study shows that the risk for glioma was tripled among those using a wireless phone for more than 25 years and that the risk was also greater for those who had started using mobile or cordless phones before age 20 years.

Though the second appears to conclude direct health risk, I'm pretty sure it's not yet any hard proof otherwise we would have seen huge lawsuits being filed all over the place.

If really harmful, what factors are in place e.g. cellular phone model, signal strength, etc?

Answer 1

The IARC has concluded that cell phones are a "possible carcinogen" due to the amount of evidence going both directions.

The gist of it is summarised on the website itself:

• Cell phones emit radiofrequency energy, a form of non-ionizing electromagnetic radiation, which can be absorbed by tissues closest to where the phone is held.

• The amount of radiofrequency energy a cell phone user is exposed to depends on the technology of the phone, the distance between the phone’s antenna and the user, the extent and type of use, and the user’s distance from cell phone towers.

• Studies thus far have not shown a consistent link between cell phone use and cancers of the brain, nerves, or other tissues of the head or neck. More research is needed because cell phone technology and how people use cell phones have been changing rapidly.

_{Mobile phone and cordless phone use and the risk for glioma – Analysis of pooled case-control studies in Sweden, 1997–2003 and 2007–2009}

Answer 2

Exposure to ionizing radiation, such as from x-rays, is known to increase the risk of cancer. However, although many studies have examined the potential health effects of non-ionizing radiation from radar, microwave ovens, cell phones, and other sources, there is currently no consistent evidence that non-ionizing radiation increases cancer risk (1).

Source: http://www.cancer.gov/about-cancer/causes-prevention/risk/radiation/cell-phones-fact-sheet#q2

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