A Nobel laureate who helped prove how dangerous chlorofluorocarbons are to the ozone layer and who served as a scientific adviser to President Obama has died. Dr. Mario Molina, a US citizen born in Mexico, passed away Wednesday at the age of 77 at his Mexico City home, the Washington Post reports. When Dr. Molina first started studying CFCs—industrial chemicals used in coolants for air conditioners and refrigerators, deodorant sprays, and other aerosols—it wasn't believed they caused any harm to the environment. Along with UC Irvine professor F. Sherwood Rowland, however, Molina discovered that CFCs actually did pose a significant danger, by depleting the ozone layer. That discovery led to the scientists winning the 1995 Nobel Prize in Chemistry, along with atmospheric chemist Paul J. Crutzen.
Now, the world says goodbye to the man called "one of the single most important contributors to climate protection in world history" by former White House climate adviser Paul Bledsoe, per Science. Molina's environmental nonprofit says he died of "unexpected cardiac problems," Reuters reports. Molina's work jump-started international efforts to curb CFCs, including 1987's Montreal Protocol, which imposed regulations on man-made chemicals that deplete the ozone layer. Environmental attorney Durwood Zaelke says Molina always remained a "gentleman," even when the chemicals industry "vilified" him for his work against CFCs. "Mario never, never changed his willingness to fight," Zaelke says. "This is who he was." (Read more Nobel laureates stories.)