The effect of mobile phone radiation on human health is the subject of recent interest and study, as a result of the enormous increase in mobile phone usage throughout the world. As of November 2011, there were more than 6 billion subscriptions worldwide. Mobile phones use electromagnetic radiation in the microwave range. Other digital wireless systems, such as data communication networks, produce similar radiation. In 2011, International Agency for Research on Cancer (IARC) classified mobile phone radiation as Group 2B - possibly carcinogenic. That means that there "could be some risk" of carcinogenicity, so additional research into the long-term, heavy use of mobile phones needs to be conducted. The WHO added that "to date, no adverse health effects have been established as being caused by mobile phone use." Some national radiation advisory authorities have recommended measures to minimize exposure to their citizens as a precautionary approach.
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