The Environmental Protection Agency sent a strong message with its appointment of Al Armendariz to the region's top post: It's time to clear the air.

The selection of the Southern Methodist University professor signaled a notable shift in the EPA's approach to regulating pollution. Armendariz, who will serve as regional administrator over Texas and four other states, has been a vocal critic of both his predecessor and state regulators.

He has been firmly entrenched in the clean-air camp, serving as a strong advocate for more stringent smog plans and tougher enforcement of pollution regulations. Plenty of Texas environmentalists are downright giddy about Armendariz's appointment. Several clean-air organizations went to bat for him during the selection process, writing to officials in Washington on his behalf.

Now they have reason to celebrate, as do all North Texans who are tired of inhaling our smog-choked air. There's little doubt that Armendariz will bring a much-needed, more aggressive approach to regulating dangerous pollutants.

Last year, when the EPA signed off on an inadequate air quality plan, Armendariz offered a tough critique, calling the proposal weak and "doomed to fail." He was right. But now Armendariz must find a way to transition from outspoken advocate to respected administrator.

Because he has been aligned with a number of environmental groups, he now needs to build confidence among state officials and industry leaders that he will be guided by science and his strong background in environmental engineering.

The Texas Commission on Environmental Quality already has telegraphed its concerns, with chairman Bryan Shaw issuing a statement that congratulated Armendariz but added: "While he has a long history as an environmental activist, I hope Dr. Armendariz recognizes that this position is too important to be used as a podium for environmental activism."

The EPA post is in part focused on enforcement, but the job also requires consensus building and ensuring that all sides have seats at the table and a say in the process. Armendariz certainly is up to this challenge, but he will have work to do as he builds relationships with those he has criticized.

With new ozone standards looming, tougher cement kiln rules pending and another round of pollution plans on the horizon, Armendariz comes to this job at a critical time. EPA officials in Washington already have publicly expressed their displeasure with Texas environmental programs, so Armendariz no doubt will have Washington's blessing to take a harder line against industries that foul our air.

For too long, Texas has shown deference to polluters, and Armendariz is poised to change that.

The transition will be interesting to watch. But most important, the result should be cleaner air.