After decades of improvement, reductions in smog-forming emissions have slowed dramatically, according to new nationwide study based on satellite measurements. The findings could explain why progress cleaning air pollution in California and other parts of the country is faltering at a time when official estimates show pollution should be steadily declining.
Emissions of smog-forming nitrogen oxides declined by 7% per year from 2005 to 2009, but fell by only 1.7% annually from 2011 to 2015, even increasing in some areas of the United States, according to the study in the Proceedings of the National Academy of Sciences.
The slowdown was discovered by an international team of researchers who compared official U.S. Environmental Protection Agency emissions inventories to actual measurements of pollution in the atmosphere from satellites and ground-based air monitoring stations.
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