The NY Times has another story about a possible link between cell phones and brain cancer.

Apparently, this controversy has flared up not because of any new scientific research, but because several neurosurgeons told Larry King that they don't hold cell phones to their ears.

There are several points to keep in mind:

1. While neurosurgeons know how to diagnose and treat brain cancer, don't expect them to have any special expertise on the molecular causes of cancer - that's not what they study. Some individual neurosurgeons do have expert knowledge on this (there is one who happens to work in the lab next door to me), because they are surgeons and scientists who study the causes of cancer. But being a neurosurgeon does not automatically make one an expert on the causes of brain cancer.

2. It's physically impossible for the energy emitted by your cell phone to directly damage your DNA. Electromagnetic energy in the microwave frequency range cannot break chemical bonds - you need to get into the UV frequency range for that to start happening, which is why too much sun exposure poses an obvious risk of skin cancer. The sun's UV rays directly damage your DNA; your cell phone's emissions don't.

3. The fact that cell phone energy can't directly damage your DNA does not exclude the possibility that the microwaves stimulate some other biological process that can lead to cancer. That is certainly possible - we have no idea what that biological process might be, but it's certainly a possibility. It's a question we need to answer empirically: are there any studies that suggest this is happening? So far, the major studies that have been done suggest that the answer is probably not.

The answer is not completely settled, especially because the big studies so far have not focused on long-term use. It's probably safe to conclude, however, that if there is a risk, it is small, since a large risk would already have been picked up in the studies that have been done.

The lesson is, unless you hear that there is new scientific evidence that cell phones cause brain cancer, don't believe neurosurgeons or anyone else who tells you that cell phones cause cancer. The more urgent problem is cell phone-induced car accidents, not cancer.