However, the "New York Times" reports it overruled the unanimous advice of its scientific advisory council for a more protective standard.

The Clean Air Act requires periodic review and the announcement updates a standard from 1997.

The standard, stated in terms of average concentrations of ozone at ground level over an eight-hour period, is now 84 parts per billion.

If it survives court review, the standard would be lowered to 75.

Last year, a scientific advisory panel recommended just 60 to 70 parts per billion.