Seven years ago representatives from General Motors, Ford, Chrysler and other car manufacturers joined President Barack Obama to announce historic new vehicle mileage standards. The industry-supported targets would have doubled the fuel efficiency of cars and light trucks in the U.S. to 54.5 miles per gallon by 2025.

But in April the Environmental Protection Agency announced plans to roll back part or all of the new standards, saying they were “wrong” and based on “politically charged expediency.” Let me explain why this terrible idea should unify Republicans and Democrats in opposition. The rollback is going to harm us economically and hurt us physically.

The Obama-era standards made sense for many reasons, starting with our wallets. It is true that each vehicle would initially cost $1,000 to $2,000 more as manufacturers researched lighter materials and built stronger vehicles. In return, though, we would save about $3,000 to $5,000 in gas over the life of each vehicle, according to a 2016 report by Consumers Union. (Because gas prices were higher in 2011 and 2012, when the standards were proposed, estimated savings back then were significantly higher—about $8,000 per car. Prices have risen somewhat since 2016.) This research will also help auto companies compete internationally.

National security and trade deficits are also reasons to keep the existing standards. Despite a growing domestic oil industry, the U.S. imported more than 10 million barrels of oil daily last year, about a third of it coming from OPEC nations. Imports added almost $100 billion to our trade deficit, sending hard-earned dollars to Canada, Saudi Arabia, Venezuela, Iraq and Colombia. Better gas mileage could eliminate half of our OPEC imports. It would also make our country safer and more energy-independent.

The biggest reason to support the fuel-efficiency standards, however, is the link between vehicle exhaust and human health. More than four in 10 Americans—some 134 million of us—live in regions with unhealthy particulate pollution and ozone in the air. That dirty air makes people sick and can even kill them. A 2013 study by the Massachusetts Institute of Technology estimated that about 200,000 Americans now die every year from air pollution. The number-one cause of those deaths—more than 50,000 of them—is air pollution from road traffic.

Air pollution, and smog in particular, is the reason California places so much emphasis on air-quality standards. The federal Clean Air Act gives the state the right to set its own standards for vehicles, pending approval by the EPA administrator. This arrangement is not new. It began with model-year 1969 vehicles. Every White House administration since then—Republican and Democrat—has approved waivers for California and allowed other states to follow California's lead.

Despite tremendous progress by companies and through targeted regulations, California still has the worst air quality in the country. According to the American Lung Association, the top four metropolitan areas for ozone pollution are those of Los Angeles, Bakersfield, Visalia and Fresno. Six of the top seven for year-round particle pollution are all in California, too. In case anyone thinks this is blue-state California's problem, think again. Air pollution is red-blue color-blind when it comes to making us sick. Other cities high on the pollution lists include Phoenix, Pittsburgh, Salt Lake City, Cleveland, Cincinnati, Dallas and my childhood home, Houston.

Here is what a rollback in mileage standards would mean: Thousands of Americans would die unnecessarily from cardiovascular and other diseases every year. Our elderly would face more bronchitis and emphysema. More children would develop asthma—a condition that, according to an estimate by the Centers for Disease Control and Prevention, affects more than one in 12. Millions of your sons and daughters have it. My son does, too.

Rarely in my career have I seen a proposal more shortsighted and counterproductive than this one. Please say there is still time to change our minds.