The stricter smog standard proposed by the Obama administration joins a string of historic — and controversial — moves by the administration to improve air quality.
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People familiar with the proposal tell The Associated Press that the Environmental Protection Agency is expected to announce Wednesday a preferred range of 65 to 70 parts per billion to reduce the amount of smog-forming pollution allowed in the air.
The agency's scientific advisers had endorsed a standard of 60 parts per billion. The current standard is 75 parts per billion, put in place by President George W. Bush in 2008.
Those familiar with the proposal were not authorized to discuss it by name ahead of the official announcement and spoke on condition of anonymity.