A panel of external scientific experts met at NIEHS March 26–28, 2018, to review the conclusions of two draft NTP technical reports. The goal of the NTP studies was to establish the potential health hazard of exposure to cell phone radiofrequency radiation (RFR).
The $30 million studies took more than 10 years to complete and are the most comprehensive assessment to date of health effects in animals exposed to RFR with modulations used in 2G and 3G cell phones; 2G and 3G networks were standard when the studies were designed and are still used for calls and texting.
The expert panel agreed with NTP conclusions that there was little indication of RFR-related health problems in mice, but the panel recommended that some findings be changed to indicate stronger levels of evidence that RFR caused tumors in rats. Working with the NTP scale of clear evidence, some evidence, equivocal evidence, and no evidence, the panel made several recommendations:
The panel agreed there were unusual patterns of cardiomyopathy, or damage to heart tissue, in exposed male and female rats and that there were increases in damage to brain tissue in exposed male and female rats, which further supported the classifications of cancerous effects in the brain. For several other tissues, including the prostate and pituitary glands, the panel agreed that tissue changes were equivocal, meaning it was unclear if any of these tumor increases were related to RFR.
In the final reports, prepared for release in November 2018, NTP concluded there is clear evidence that male rats exposed to high levels of RFR developed cancerous heart tumors and that there is also some evidence of tumors in the brain and adrenal gland of exposed male rats. For female rats, and male and female mice, the evidence was equivocal as to whether cancers observed were associated with exposure to RFR.
The final reports represent the consensus of NTP and the panel of external scientific experts who reviewed the studies in March 2018.