That it may cause stress related symptoms in humans is completely comprehensible, particularly among heavy and compulsive users. The Precautionary Principle Science at present cannot affirm whether cellular phone poses undue health risk. Nor are there evidence to prove that it is completely harmless. There are no randomized control trials stating that cellular phone improves economy, quality of life, or even personal communication. Personally, I find the precautionary principle a useful guidance under the circumstances.
People have a duty to take anticipatory action to prevent harm.
The burden of proof of harmlessness of a new technology, process, activity, or chemical lies with the proponents, not with the general public. The Medical Advice Avoid dial and drive as much as drink and drive. Use the mobile phone only when line phones are not available. For heavy users, consider a hands free set. The inverse square law applies here.