>> environmental factors take decades to see their effect, not a few years. >> reporter: if it may take decades to get a clearer answer, what can we say about cell phone safety now? scientists here in san jose, california are trying to answer that very question. >> one of the things we have to do first is literally put the brain inside the head. >> exactly. it's very light now. >> reporter: the fcc requires all cell phones emit below 1.6 watts per kilogram of radiation. in order to test for, that scientists here try and mimic the human brain, with salt, sugar, and water. let me show you how they do this test. this is a model. this is supposed to proximate the human skull, an adult male. this is my phone we've attached there, connected at the angle most people would speak with. and inside over here, this liquid inside represents liquid brain. the phone is making a call.