Readers share a report: In the event of a dirty bomb or a nuclear meltdown, emergency responders can safely tolerate radiation levels equivalent to thousands of chest X-rays, the Environmental Protection Agency said in new guidelines that ease off on established safety levels. The EPA's determination sets a level ten times the drinking water standard for radiation recommended under President Barack Obama. It could lead to the administration of President Donald Trump weakening radiation safety levels, watchdog groups critical of the move say. "It's really a huge amount of radiation they are saying is safe," said Daniel Hirsch, the retired director of the University of California, Santa Cruz's program on environmental and nuclear policy. "The position taken could readily unravel all radiation protection rules." The change was included as part of EPA "guidance" on messaging and communications in the event of a nuclear power plant meltdown or dirty bomb attack. The FAQ document, dated September 2017, is part of a broader planning document for nuclear emergencies, and does not carry the weight of federal standards or law.