Reportable substances are any that might reasonably be expected to cause adverse human health effects, which include, among others, ammonia, all pesticides, chlorine, sodium hydroxide, and hydrochloric, nitric, phosphoric, acrylic, and hydrofluoric acids. Petroleum releases, however, are specifically excluded. Reportable releases are all those in which an actual release occurs and those where there is only the threat of a release but some action is taken as a result, such as evacuating persons from the area. Releases are defined as transportation- related when they have occurred during surface, air or water transport. Fixed-facility releases are defined as releases that occur at industrial sites, schools, farms or any other permanent location.
All events are either fixed facility or transportation-related.
An evacuation is defined as an event in which at least one person had to leave home or place of work. Injury data is gathered for all injuries related to the event. Releases were categorized by season, time of day, period of the week, type of area where the release occurred, and amount of chemical released. Period of the week was categorized as weekday or weekend. We categorized all ammonia release sizes as at least 100 pounds or 10 gallons or less than these quantities.