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First, it is uncertain how to apply the results obtained in rats and 
mice to humans. Second, many of the studies that showed 
increased tumor development used animals that had already 
been treated with cancer-causing chemicals, and other studies 
exposed the animals to the RF virtually continuously—up to 22 
hours per day.
For the past five years in the United States, the mobile phone 
industry has supported research into the safety of mobile 
phones. This research has resulted in two findings in particular 
that merit additional study:
1
In a hospital-based, case-control study, researchers looked 
for an association between mobile phone use and either 
glioma (a type of brain cancer) or acoustic neuroma (a 
benign tumor of the nerve sheath). No statistically 
significant association was found between mobile phone 
use and acoustic neuroma. There was also no association 
between mobile phone use and gliomas when all types of 
types of gliomas were considered together. It should be 
noted that the average length of mobile phone exposure in 
this study was less than three years.
When 20 types of glioma were considered separately, 
however, an association was found between mobile phone 
use and one rare type of glioma, neuroepithelliomatous 
tumors. It is possible with multiple comparisons of the same 
sample that this association occurred by chance. Moreover, 
the risk did not increase with how often the mobile phone 
was used, or the length of the calls. In fact, the risk actually 
decreased with cumulative hours of mobile phone use. 
Most cancer causing agents increase risk with increased 
exposure. An ongoing study of brain cancers by the