Current scientific evidence indicates there is no link between using a portable (laptop) computer and cancer. Most of the theories about laptops and cancer relate to heat, electromagnetic radiation, or radiation from wireless networks (WiFi). One theory is that men who use laptops on their laps could be at greater risk of testicular cancer because of the heat near the scrotum, which could damage cells. While some studies show heat (from various sources, not just laptops) can affect a man’s sperm and fertility, there is no research linking heat from laptops to cell damage or cancer. There have been cases of ‘toasted skin syndrome’ (mottled skin condition caused by long-term heat exposure) in people who used laptops resting on their legs for long periods. Some claim that such damage could potentially lead to skin cancer, but there is no evidence to prove this. Computers, like many other electrical appliances, produce electric and magnetic fields, however most are in the extremely low frequency range. According to the World Health Organisation, the field strengths are far below international exposure limit guidelines and there is no scientific evidence of health effects from long-term, low-level exposure.