The threshold that applies to the general population and is intended to approximate the level of dose or exposure at which the sensitive groups within any large population would begin to show an increase in mortality. The definitions below are intended only for use in the facility Hazards Assessment process. For purposes of conducting facility Hazards Assessments, the TEL should be interpreted as follows: For radiological releases: A projected dose (TEDE) of about 100 rem to reference man, where the projected TEDE is the sum of the EDE from exposure to external sources and the CEDE from inhalation during the early phase. The use of 100 rem TEDE as an approximation of the lethality threshold is quite conservative. Radiation effects studies have estimated a 5 percent risk of early fatality following an acute dose of 140 rem, with a smaller but indeterminate risk expected for doses below that level. Little if any risk of early fatality would be associated with 100 rem TEDE if the dose were received over a period of time from radioactive material taken into the body. For non-radiological releases: A projected 15-minute average concentration of the substance in air that equals or exceeds the ERPG-3 or alternative value for that substance