Editor’s Note: In mid-May, Scientific American will announce the winners of this year’s Scientific American 10. Every Monday we will profile a previous Scientific American 50 winner.

Year in Scientific American 50: 2002

Recognized for: Bill Becker earned a place on the award's inaugural list as an environmental policy leader for his work urging a reduction in auto emissions. As executive director of the National Association of Clean Air Agencies (NACAA, an association of state, territory and city agencies that helps to manage policy across the country), he coordinated efforts to create model air pollution regulations that could be—and were—turned into law.

What has happened to his work:
Since the successes cutting car emissions, Becker and the NACAA have scaled up. Working with the U.S. Environmental Protection Agency (EPA) and other groups, they've helped to pass two more key rounds of emission regulations, including one targeting large trucks and another taking aim at "non-road sources" (which includes less obvious culprits such as construction and farm equipment).

As part of NACAA's mission to help clean air agencies, the group has written model rules that states can adopt to control emissions and air pollution. "The last administration did a terrible job of regulating mercury from power plants," Becker notes. "And we developed a model rule that we provided to states and localities around the country." In 2005 the group announced a model rule—more stringent than reductions mandated by the EPA—to curb mercury emissions from coal-fired power plants at least 90 percent by 2012. Since then, about half of the states have adopted it, Becker says.

What he is doing now: More recently, Becker and the NACAA have been pushing for stricter emission regulations for trains and ships as well as offering recommendations [pdf] to the Obama administration, such as advocating for a science-based revision of National Ambient Air Quality Standards. "When the federal government is unable or unwilling to do its job, we'll step in," he says. "We are going to make sure that the public health is fully protected."