By now you may have heard that cell phones are "possibly carcinogenic to humans." That's according to the World Health Organization and something some scientists have suspected for a while. But now that it's coming from the WHO, those who have questioned the safety of cell phones have significant international support.But why "possibly"? What is that supposed to mean? The latest judgment from the WHO sounds a little wishy-washy, and that's because of the inconclusive nature of the scientific studies on this subject.The available research on the health effects of cell phone is retrospective. That means scientists are looking into the past at the association between people's behavior and brain health, rather than designing an experiment that will require a controlled setting. Researchers can't control retrospectively how much any individual uses a cell phone, or regulate other environmental factors that might be detrimental to brain health, or even know how far away from the head different people hold their cell phones. Remember that the amount of radiation you receive is related to distance-squared from the source, so the further away your phone is physically, the safer you would be.In a closer-to-ideal experiment regarding cell phone use, scientists would be able to monitor exact cellphone use of particular users over a given time period under controlled conditions, and track their health as well. That would be a prospective study. They would look at particular groups of users - those with high, medium and low usage - and compare health effects. They would know who has what kind of phone, make sure that person kept the same phone during the entire duration of the experiment, and figure out a way to standardize the phone's distance from the head.The Interphone study, the largest scientific look at the cell phone health question to date, is a retrospective study. It also is partly industry-funded, and while the WHO's International Agency for Research on Cancer coordinates it, several researchers who analyze the data receive money from the mobile phone industry.In May 2010, Interphone published results indicating no connection between cancer and phones. But it defined "highest" exposure levels as using a mobile phone half an hour a day over a 10-year period. In the appendix of the study, published only online, the risk of developing a glioma brain tumor about doubles if you are using a cell phone over a 10-year period.In general, the Interphone study has many flaws. Among them, participants self-reported how much they used their phones, and memory isn't always accurate. Also, Interphone does not include children and young adults, who could be at increased risk of brain disease from cell phone radiation. Interphone also fails to address cordless phone use. But the bottom line is that while it doesn't prove with absolute certainty that anything causes anything, it is still a reason to pause and think about your cell phone use.Also, in February, a National Institutes of Health study found that cell phone use is associated with increased brain cell activity, although no one really knows what that means for longterm health.As you can see, there are a lot of different factors involved here, and it's hard to know what to make of this data. CNN's own Dr. Sanjay Gupta says he uses a wired earpiece when talking on a cell phone. If you are concerned about cell phone safety, continue to check in with CNNHealth.com and "The Chart" for the latest reporting on medical and scientific studies and keep in mind, if leading neurosurgeons are using wired ear pieces, it may be a good idea to do the same. Here are some tips for minimizing cell phone radiation.Source: CNN