The head of the World Health Organization Ms. Gro Halem Brundtland, has warned parents against letting their children spend too much time on mobile phones and says their electromagnetic waves give her a headache. Her comment have given Irish mobile phone manufacturers a pain of their own as once again they are moved to insist there is no conclusive evidence that their products are harmful to human health. Ms. Brundtland, a medical doctor and mother of four children said yesterday she does not own a mobile phone. She forbids any one who works in her Geneve office to use one to protect herself from electromagnetic radiation waves. "If you enter my office you are invited by me. No one who is invited would like to give me headaches" Ms. Brundtland said at a news conference in Oslo wher she attended an international conference on cancer. "I would be cautious about letting children use mobile phones for hours every day because we don`t know enough about the damage" she said.