In the USA, current regulations require that new facilities for the storage of high-level nuclear waste be able to guarantee its conformity to current detailed legal standards for 10,000 years (equivalent to the entire span of recorded history), an impossible scientific task. This means that, whereas underground storage of high-level radioactive waste such waste is generally considered the safest option available, construction and operation of underground storage facilities is not possible, leaving the waste at the surface where the risks of eventual public exposure are almost certainly higher.