The health effects of radiation are dependent on the cumulative amount, the energy and the particle makeup of radiation. Radiation is considered dangerous to life as low doses of ionizing radiation can cause damage to DNA causing cell mutations. Doses of between 100 to 600 rad (measurement for radiation) can cause stomach discomfort, fatigue and vomiting. However, doses of 200 to 800 rad without medical assistance has a 50% of causing death within 60 days. Doses of 800 or more rad are almost certainly lethal without treatment.