Environmental groups are suing the Obama administration for scrapping a stricter limit for smog-forming pollution.
The groups say the administration violated the law by putting politics ahead of protecting public health.
The lawsuit was filed Tuesday in the federal appeals court in Washington by four environmental and public health advocacy groups.
The White House announced last month that it wouldn't support setting a new standard for ground-level ozone even though the Environmental Protection Agency and its scientific advisers said that step was necessary to protect public health.
The White House was under pressure from business groups and Republicans, and said a new standard would create "needless uncertainty" at a time when the economy was struggling.
The new standard would have replaced one set in 2008 by President George W. Bush.