One problem for medical care on Mars missions, is the difficulty in returning to Earth for advanced care, and providing adequate emergency care with a small crew size.[1] A crew of six might have only trained at the level of Emergency medical and one physician, but for a mission that would last years.[18] In addition, consultations with Earth would be hampered by a 7 to 40 minute time lag.[18] Medical risks include exposure to radiation and reduced gravity, and one deadly risk is a Solar Particle Event that can generate a lethal dose over the course of several hours or days if the astronauts do not have enough shielding.[18] The effect of radiation on stored pharmaceuticals and medical technology would have to be taken into account also.[18]