Commentary on Earth Day and the Relationship to Historical Developments in Air Pollution Control and Scientific Next Steps

Since 1970 we have celebrated Earth Day to commemorate the start of the modern environmental movement. Scientists contributed to technology development which created pollution in the first place but also contributed to significant advances in data and discoveries to abate that pollution. I focus here on the causes of air pollution and the contributions of Arie Jan Haagen-Smit to determine the cause of smog. His efforts were followed by those of Houdry, Keith, Mooney, and many others to invent technology including the three-way catalytic converter in use at scale today to abate air pollution. These discoveries continue, and I discuss future areas of air pollution in need of new development including methane remediation.