Mobile phone manufacturers test their devices for compliance with the exposure limits and report this value (known as the Specific Absorption Rate or SAR). These independently set limits also include large safety margins (50 fold or 5000%) to cover any unknown health impacts. Manufacturers have provided SAR information since 2001 on company websites and in manuals. The MWF also runs a SAR reporting program: www.sartick.com
Although the biggest relative exposure to radio frequency electromagnetic fields comes from holding a mobile phone next to your head to make a phone call, in everyday use modern smart phones operate at a fraction of international safe exposure limits. This is because the network instructs the device to only use the minimum power needed to make and maintain a good connection.
Further information about SAR is available on sartick.com or from the United States Federal Communications Commission.