Since 1990, the Clean Air Act (CAA) has defined a list of Hazardous Air Pollutants (HAPs), requiring the U.S. Environmental Protection Agency (EPA) to set emissions standards for many sources of these pollutants. HAPs include heavy metals, organics, and other airborne pollutants that are not otherwise regulated as “criteria” air pollutants (such as carbon monoxide, particulate matter, and ground level ozone). The 1990 CAA Amendments included a list of 189 HAPs (later corrected to 188), and empowered EPA to modify the list. In the intervening decades, EPA conducted rulemakings and deleted four initially-listed HAPs, but until 2022 had never added a new HAP. However, EPA has now added 1-bromopropane (1-BP) as a new HAP, effective February 4, 2022.
