Nothing makes our air dirtier than the cars we drive.

“Of all the sources of air pollution in the state, mobile sources contribute 41 percent,” said Paul Farrell, assistant director of air planning at the state Department of Energy and Environmental Protection. “They’re the biggest contributor by far.”

If those cars burn gasoline more efficiently, less pollution results. Our air will be healthier, with lower levels of the pollutants that create ozone and force people with asthma and chronic obstructive pulmonary disease to stay indoors.

“Who wants to sit next to the tailpipe of a car?” said Dr. Gregory Dworkin, a pediatric pulmonologist at Danbury Hospital.

Which is why the Trump administration’s decision last week to walk away from the federal Environmental Protection Agency’s plans to tighten those standards seems both totally expected — given Trump’s stand on environmental issues so far — and totally wrong-headed.

Instead of pushing American automakers to be more innovative, Trump and EPA commissioner Scott Pruitt are letting them slide. Which means American cars will be more expensive to drive and less attractive on world markets.

Claire Coleman, an attorney who specializes in climate and energy issues for the Connecticut Fund for the Environment, said the effort to increase fuel efficiency standards has actually been good for car companies.

“It’s kept our automakers more competitive,” Coleman said. “Back in 2011, they were saying this was a great thing for them.”

If there is a good catch in all this for Connecticut, it is this: The federal Clean Air Act allows California — and no other state — a waiver to set its own stricter air and auto emissions standards. Other states can piggyback onto that waiver by passing laws saying they’ll abide by the California standards.

So far, 13 states, including Connecticut, have done that. For the moment, the Trump administration seems willing to let that stand.

“It’s a very good thing,” Coleman said.

All the New England states except New Hampshire have adopted the California standards, as have New York, New Jersey, Pennsylvania and Maryland. So there is a Northeastern effort t to clean up the air.

But Connecticut is — geographically, demographically, and atmospherically — a tough place for this to work. Prevailing jet stream winds blow pollution here from big Midwestern power plants.

Connecticut also gets a flow of auto pollution generated in the Interstate 95 corridor from Washington, D.C., northward. It’s also a small, densely populated place with a lot of cars of its own.

The state adopted the California standards in 2004; they went into effect in 2008. Because it takes at least a decade for older, dirtier cars to go to the Great Junkyard in the Sky, Connecticut might not yet be seeing the benefits of the new standards.

And because ground-level ozone forms on hot summer days with lots of sunshine, cool, wet summers can lower the number of bad air days in the state.

Karl Wagener, the director of the state Council on Environmental Quality, said state ozone levels have stayed about the same for the past 10 years. But cleaner cars have obviously helped things from getting worse, he said.

“If we had cars like we did in the 1970s? Good God, it would be awful,” Wagener said.

And, lest anyone forget, dirty air has a human cost. Ozone, for example.

“It’s a bronchoconstrictor,” said Dworkin of Danbury Hospital. “It causes the airways of the lungs to get smaller.”

Which means people with compromised lungs suffer if they go out when ozone levels are high.

“It can set off an asthma attack,” Dworkin said of ozone. “It can inflame and damage the airways.”

Farrell of the DEEP said if carbon dioxide emissions aren’t checked and climate change accelerates, a host of other medical problems are coming our way.

Climate chance could mean much more erratic weather, with drier, hotter summers and more bad air days.

“There could be more wildfires,” Farrell said. “There could be new infectious diseases.”

If the California waiver stands — a serious if — cars sold in Connecticut will get cleaner. Fuel efficiency will save people money. And cars will burn less fuel, releasing less greenhouse gas.

So, wait and see if changes that make no sense continue, or whether they get fought in the courts.

“There are environmental issues you could have a reasonable debate about,” Wagener said. ‘But not this.”

Contact Robert Miller at