This week, after three days of live broadcast peer review sessions, experts concluded that a number of federal studies have provided "strong evidence" that cell phone radiation causes heart cancer in male rats.
Whether cell phone use is a cancer risk. So far, the federal government and mobile phone manufacturers have assumed that mobile phones can not naturally be carcinogenic due to their non-ionizing radiation. While ionizing radiation – the species associated with, inter alia, X-rays, CT scans, and nuclear power plants – causes cancer in sufficiently high doses, it was believed that non-ionizing radiation does not emit enough energy to break chemical bonds. This meant that it could not damage the DNA and therefore could not lead to cancer-causing mutations.
But the US National Toxicology Program study pair found "clear evidence" that radiation exposure in male rats resulted in cardiac tumors and found "some evidence" that it caused tumors in the brains of male rats. (Both are positive results: the NTP uses the terms "clear evidence", "some evidence", "ambiguous evidence" and "no evidence" when inferences are drawn.)
Tumors were also found in the hearts of female rats but they did not rise to the level of statistical significance and the results were described as "ambiguous", in other words, the researchers could not be sure that the radiation caused the tumors.
The next scientific step will be Determine what that means to humans. The peer-reviewed papers are forwarded to the US Food and Drug Administration, which is responsible for identifying human risk and issuing guidelines to the public, and the Federal Communications Commission, which develops security standards for mobile phones. The FDA was part of the group of federal agencies that commissioned the trials in the early 2000s.
Ronald Melnick, senior NTP toxicologist who designed the studies (and retired from the agency in 2009), says it's unlikely that a future study could conclude with certainty that the cell phone there is no risk for humans. "I can not see any proof of a negative that has ever come out of future studies," says Melnick.
He believes that the FDA should publish guidelines based on the results of the rat studies. "I would find it irresponsible not to give the public any clues," says Melnick. "Keep your distance from this device from your children Do not sleep with your phone near your head Use wired headsets This is something the agencies could do now."
Re-evaluation of data
When the draft results were released earlier this year, all results were labeled as "ambiguous," which the study means The authors felt that the data was not clear enough to determine if the radiation had any health effects or not. However, the group of peer reviewers (brain and heart pathologists, toxicologists, biostats and engineers among them) re-evaluated the data and improved some of the conclusions to "some evidence" and "clear evidence".
Peer review is an important part of any scientific study; it brings several more expert lives into the room to review a study for possible problems. Melnick describes the reviewers' decision to change some conclusions as an unusual step; "It's quite unusual for the peer review panel to change the final decision," he says, noting that peer testers downgrade the results rather than upvaluing them. "When NTP presents its results, the peer review is usually comparable to the outcome in almost all cases." In this case, the reviewers felt that the data – in combination with their knowledge of cancer and the study design itself – were significant enough to improve some of the outcomes.
The peer reviewers had some problems with the study; some wished it had taken longer (the rodents were exposed to radiation for two years), for example to detect later developing tumors, but others on the panel noted that the longer a rodent lives, the more likely it is to have tumors independently To develop the radiation, which makes it difficult to find the signal in the noise. Others wanted the researchers to dissect the rodent brains more than they did to find hard-to-find tumors. However, they found that science is an iterative process; the study was not perfect, but it is better than anything that has been done so far.
Overall, the peer reviewers praised the study for their rigorous conception and execution. George Corcoran, the head of the Department of Pharmaceutical Sciences at Wayne State University, said the study was "gold standard for design and behavior" and "consistently comprehensive and robust."
What studies actually found
The papers found that, in male rats, there was "unequivocal evidence" that exposure to cell phone radiation increased risk for a rare type of malignant tumor called schwannoma in connective tissues that surround nerves inside (they found "ambiguous" evidence of the same in female rats). They also found "some evidence" that the radiation in the male rats caused malignant glioma, a type of brain tumor that affects glial cells.
There was also "ambiguous" evidence that it increased the risk of heart disease and resulted in evidence of DNA damage. Baby rats born to mothers during the experiment had a lower birth weight. The researchers also found a statistically significant increase in lymphoma (cancer of the lymph nodes) in female mice and increased rates of liver cancer in the male mice. All these findings were described as "ambiguous".
As we have already noted, animal studies can not perfectly reproduce the use of mobile phones; You can not make a rat hold a tiny cellphone or put it in your pocket, for example.
But the results of these two rat studies are consistent with those of the largest mobile phone radiation human study to date, INTERPHONE. The INTERPHONE study, published in 2011, was a collaborative effort by researchers at 16 institutions in 13 countries and found that the heaviest mobile phone users developed gliomas more frequently – the same kind of brain tumor that the NTP study found in male rats. "So there is a match between human and animal data," says Melnick.
In response to the INTERPHONE report, the International Agency for Research on Cancer, the World Health Organization's cancer department, classified mobile phone radiation as 'potentially carcinogenic to humans' in 2011. (Melnick also sat on the panel that made this decision
The INTERPHONE authors reported various issues with their data, and the study was based in part on interviews with people who already had brain tumors so that they could be recalled biased and cause much insecurity. [HoweverMelnicksaystheINTERPHONEstudylookedattheratesofvarioustypesofbraintumors(meningiomaforexample)theydidnotfindanydifferenceinheavymobilephoneuserspointingoutthatiftherewasarecallbias"Whywasitthisguyandnotthisothertypeofcancer?"
The FDA will take the next step in the Be the human risk and the results interpret the public. "We take a responsible approach," said Edward Margerrison, director of the FDA's science and technology bureau, on Wednesday, according to News & Observer. "We will not kneel for anything."