The U.S. Environmental Protection Agency has set more stringent new air-quality standards for sulfur dioxide (SO2). In a final regulation announced on June 3, EPA is jettisoning the current standard, which is 140 parts per billion over 24 hours, in favor of a one-hour, 75-ppb level. The estimated cost to fully implement the new standard by 2020 is $1.5 billion, EPA says. The agency says the new one-hour standard will protect public health by reducing exposure to high short-term concentrations of SO2, which is commonly emitted from powerplants and industrial facilities. EPA also is revising ambient-air monitoring requirements for SO?.