For North Texas, another ozone season is behind us, another failure to meet federal clean air standards -- even under an old standard that we almost but didn't quite meet in 2009 and 2010.The region hasn't had healthy air since an ozone standard was set in 1997. Ozone forms on summer days when pollutants are baked in the hot sun, and it's a major irritant for people with respiratory or heart problems.President George W. Bush's administration sought a tougher ozone standard in 2008. President Barack Obama's administration set that new standard aside shortly after he took office and studied an even tougher one.Obama decided against that plan, telling the Environmental Protection Agency to use the 2008 Bush standard, at least until the regular cycle of clean air requirement-setting comes around next year.If all that back-and-forth leaves you dizzy, just remember this: Our air quality is a long way from where we need it to be, even as both Republican and Democratic administrations have pushed for lower ozone levels.The good news is that North Texas air is cleaner than it used to be. Ozone declined from 102 parts per billion in 2000 to 86 parts per billion by 2010. That almost met the 1997 standard for ozone concentrations to be less than 85 parts per billion, but the EPA still designated North Texas a "serious" nonattainment area.The ozone measure bounced back to 90 parts per billion in the overheated summer of 2011, then dropped to 87 this year.But we're now under the 2008 Bush standard, which allows no more than 75 parts per billion. The Texas Commission on Environmental Quality must submit a plan by 2015 to show how the region will meet that standard.Much of the region's improvement has come because vehicle owners have replaced their cars and trucks with newer, less-polluting models. Critics say the only way to meet the 2008 standard -- or an even tougher one that could result from the coming regulatory review -- is to crack down more on industrial polluters and the oil and gas industry.It's going to be hard, but we can't settle for dirty air.