Northern California and Nevada may need to ask for exemptions to a federal air quality rule the EPA is expected to issue this week, according to a NASA-led study.
Ozone pollution – the main ingredient in smog - can be in a region but not originate from there or from human-produced sources. It’s called background ozone, and apparently Northern California and Nevada have a lot of it.
A new NASA study shows levels of background ozone generated 77 percent of total ozone in the regions. The EPA has proposed lowering the ozone standard from 75 parts per billion to between 65 and 70.
The study's findings are particularly important because wildfires and transported pollution can cause background ozone to approach the proposed new limit. The Clean Air Act allows states to request an exemption - if they can show that it’s due to ozone from outside the country or from natural causes.
The EPA will make its final ruling by Thursday.
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