Asbestos, a cancer-causing construction material, has been found in 96 of 100 school buildings across South Korea, a report showed Friday, raising concerns about the threat the hazardous material poses to students\' health. Asbestos exposure becomes a health concern when high concentrations of asbestos fibers are inhaled over a long time period, causing asthma, respiratory disease or even lung cancer. South Korea has banned the use of the material in new construction projects since the late 1990s for health and safety reasons.