Tablet computers are fairly new, but their use has grown exponentially since they were first brought on the market. In the past, computers like desktop PCs were very big and bulky. They emitted Electromagnetic Radiation (EMR) radiation, but users were relatively safe, because the computer was often used a safe distance away from the body.
Today, tablets produce many times the computing power than older computer models, yet are extremely portable and easily fit into your laps and hands. Tablet computers are also used much closer to the body, thus creating health risks that did not exist 10-20 years ago.