 At present, we don't know precisely the degree to which the risk of cancer and other adverse health effects are increased by the exposure to the radiofrequency fields from cell phones. I explored the brain tumor data previously. What other potential adverse health effects might there be? For example, what about the effect on brain function? The dramatic increase in the use of cell phones has generated concern about possible negative effects of the radiofrequency signals delivered to the brain. However, whether acute cell phone exposure affects the human brain is unclear, so researchers decided to put it to the test, using PET scan technology and did find elevated brain activity in the region of the brain closest to the antenna after 50 minutes of exposure to a cell phone call. But what does that actually mean? Well, it's evidence that the human brain has at least some sensitivity to the effects of cell phone radiation. The increased metabolism in brain regions closest to the antenna suggests the brain absorption of cell phone emissions may enhance the excitability of brain tissue. The potential health consequences of this are unknown, noted the accompanying editorial, though suggests an effect on brain functioning is possible, potentially affecting neurotransmitter and neurochemical brain activities. Maybe that can explain the changes in psychological test outcomes observed after exposure to cell phone radiation. Wait, what? Earlier studies failed to find an effect of short-term cell exposure on human cognitive performance, but this 2017 review noted that several studies now indicate an increase in things like brain tissue excitability, which may translate out into measurable cognitive effects. This cortical excitability, excitability of the outer layer of the brain, might underpin disruptions in sleep tied to cell phone exposure, for example, but may also improve reaction time. If you expose people to active cell phones while playing like a computer game, they can actually respond faster compared to sham exposure, meaning like placebo exposure, same scenario, but with the cell phone turned off. So the industry can be like, okay, okay, so cell phone radiation does affect brain function after all, but the effects are positive. A decrease in reaction time upon exposure to microwave radiation from cell phones can help people better respond to different threatening situations, decreasing errors perhaps, reducing destructive accidents. But the difference in reaction time was just a few thousands of a second. Put all the studies together, and the effects seem so small that implications for human performance in everyday life can be practically ruled out. There was a study that found that heavy cell phone users did better on a test of the ability to filter out irrelevant information, but this improvement in focused attention may just be because heavy cell phone users have lots of practice carrying on conversations in crowded places. Overall, electromagnetic fields from cell phones do not seem to induce cognitive or fine motor skill effects. Nonetheless, one has to worry about the existence of sponsorship and publication biases, meaning maybe studies funded by cell phone companies were designed in a way to skew the results, or were quietly shelved and never published if they showed anything negative. And indeed, if you compare the source of funding and results of studies of the health effects of mobile cell phone use, studies funded exclusively by industry were substantially less likely to report significant health effects. It would look suspicious, though, if all the industry studies just showed no effects, so some have accused the industry of taking obfuscation to a new level. Although, yes, the industry funded studies were significantly more likely to show no effects, as one might expect, no two studies reported the same effects, and the few attempts at replication failed. Thus, the apparent message of the studies dovetails well with the industry's position that there are no reproducible biological effects. So they're not just denying the existence of effects. If the industry funded studies all just universally found no effects in contrast to independent research, the industry research program could have been more easily dismissed. Of course, they all couldn't come out showing health effects. That would have been bad for business. So by instead coming up with this wide hodgepodge of conflicting results, they can better protect themselves, perhaps all part of a well-designed legal strategy to fight off lawsuits. But we may never know. We do know that when the World Health Organization came out saying cell phones may be causing brain tumors, the cell phone industry went into damage control to attack the agency similar to when the WHO came out against second-hand tobacco smoke. Sowing confusion and manufacturing doubt is just what industries tend to do.