In his last act as EPA Administrator on Friday, Scott Pruitt vacated an Obama-era ruling that dramatically restricted sales of polluting "glider" trucks.

Pruitt's earlier efforts to repeal the ruling were opposed by a broad, bipartisan coalition of environmentalists, public health advocates, truck makers, and some Republican representatives from states with other manufacturing interests.

The glider trucks, led by manufacturer Fitzgerald Glider Kits, are new truck bodies and frames fitted with old, diesel engines that pre-date emissions controls.

Western Star semi tractor used to promote Fitzgerald Glider Kits

Western Star semi tractor used to promote Fitzgerald Glider Kits

Those engines emit as much as 43 times the carcinogenic particulate matter and 13 times as much smog-forming nitrogen oxides as modern diesel truck engines. In the presence of sunlight, nitrogen oxides form smog, which has been linked to asthma.

Fitzgerald sold as many as 3,000 gliders in 2017, and under the Obama Administration the EPA ruled that each glider-kit manufacturer would be limited to 300 per year. 

The loophole in federal emissions regulations was intended to allow the reuse of relatively new and expensive truck engines after an accident destroyed the truck. Manufacturers such as Fitzgerald. however, turned it into a thriving profit center after new emissions controls were required on heavy diesel highway engines starting in 2007, and they saw a market for trucks with older engines that were simpler, cheaper, and easier to repair.

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To justify closing the loophole, Pruitt had cited a study by Tennessee Technical University showing the trucks did not pollute significantly more than newer trucks, but the industry funded study was not peer reviewed and was later retracted by the University.

Manufacturers such as Virginia-based heavy-truck maker Volvo, Illinois-based Navistar, and Cummins, which makes diesel engines in Indiana, all opposed Pruitt's efforts to keep the loophole open, as did UPS, which buys thousands of long-haul trucks. Name-brand truck and engine makers have invested millions in developing the cleaner engine technology.

“I cannot recall an issue with such a breadth of opposition," Paul Billings, national senior vice president for advocacy at the American Lung Association told the Washington Post.

Fitzgerald Glider Kits headquarters in Crossville, Tennessee

Fitzgerald Glider Kits headquarters in Crossville, Tennessee

“This just does not make any sense to me,” Christine Todd Whitman, the first EPA head in the George W. Bush Administration, told the New York Times. “Everybody breathes the same air, Democrats or Republicans. This is about keeping people healthy."

According to a New York Times report, Fitzgerald executives and family members contributed $225,000 to the campaign of Tennessee Senator Diane Black when she ran for governor. Senator Black then introduced an exemption for Fitzgerald Glider Trucks in Congress.

On his way out the door of the EPA, Pruitt announced that "The Agency is exercising its enforcement discretion in 2018 and 2019," meaning it will refrain from enforcing the glider rule for two years.