In one type of study, called a case–control study, cell phone use is compared between people with these types of tumors and people without them. In another type of study, called a cohort study, a large group of people who do not have cancer at study entry is followed over time and the rate of these tumors in people who did and didn’t use cell phones is compared. Cancer incidence data can also be analyzed over time to see if the rates of brain tumors changed in large populations during the time that cell phone use increased dramatically. These studies have not shown clear evidence of a relationship between cell phone use and cancer. However, researchers have reported some statistically significant associations for certain subgroups of people.

A decline in male sperm quality has been observed over several decades.[11][12][13] Studies on the impact of mobile radiation on male fertility are conflicting, and the effects of the radiofrequency electromagnetic radiation (RF-EMR) emitted by these devices on the reproductive systems are currently under active debate.[14][15][16][17] A 2012 review concluded that "together, the results of these studies have shown that RF-EMR decreases sperm count and motility and increases oxidative stress".[18][19] A 2017 study of 153 men that attended an academic fertility clinic in Boston, Massachusetts found that self-reported mobile phone use was not related to semen quality, and that carrying a mobile phone in the pants pocket was not related to semen quality.[20]
Cooper's prototype arrived on the market a decade later at the staggering price of $3,995. Designed by Rudy Krolopp, it was known as the Motorola DynaTAC 8000X, or simply "the brick.” Featuring 20 large buttons and a long rubber antenna, it measured about 11 inches high, weighed almost 2 pounds, provided one hour of battery life and could store 30 phone numbers.

In a February 2 statement, Jeffrey Shuren, director of the FDA’s Center for Devices and Radiological Health, wrote that despite the NTP study’s results, the combined evidence on RF exposure and human cancer—which by now amounts to hundreds of studies—has “given us confidence that the current safety limits for cell phone radiation remain acceptable for protecting the public health.” Chonock says that for him, evidence from the Ramazzini study does not alter that conclusion. “We continue to agree with the FDA statement,” he says.

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 in humans (2).