 Nevertheless, there have been several accidents involving flasks, including derailments, collisions, and even a flask being dropped during transfer from train to road, with no leakage having occurred.Problems have been found where flasks "sweat", when small amounts of radioactive material absorbed into paint migrate to the surface, causing contamination risks.Studies identified that 10–15% of flasks in the United Kingdom were suffering from this problem, but none exceeded the international recommended safety limits.