Experts are divided over the effects on human health of the electro-magnetic radiation emitted by mobile telephone transmitters. According to Loukas Margaritis, director of the cell biology and biophysics department at Athens University, most effects of exposure to mobile telephony radiation, such as headaches and short-term memory loss, are mild. Healthy cells can usually use their defensive mechanisms to adapt to such exposure without suffering damage. But this is no guarantee, since some groups in the population – such as children, the infirm, the elderly and people with pacemakers – are more vulnerable to radiation. Efthymios Karabetsos, of the non-ionizing radiation office of the National Atomic Energy Commission, argues that exposure to electro-magnetic radiation should be evaluated at all points that affect the public. Also, Karabestos says it must be established whether the legal limits of exposure are being adhered to.