When Biden administration officials unveiled a first-in-decades crackdown on pollution from heavy-duty trucks last month, they touted the requirements as a major step toward cleaner air and environmental justice.
The measure compels engine makers to adopt technology designed to curb tailpipe emissions. Tucked inside the 1,200-page rule, though, is an exemption -- pushed by manufacturers including Daimler Truck North America and Navistar International -- that threatens to obliterate the regulation's smog-cutting potential.
Since pollution-control systems don't work as well in chillier conditions, the provision is designed to relax some standards as temperatures drop. But the shift begins at a balmy 77 degrees Fahrenheit -- warmer than the average temperature across most of the continental United States, even during summer.
For Dave Cooke, a senior vehicles analyst at the nonprofit Union of Concerned Scientists, the joke writes itself. It's "a loophole big enough to drive a polluting semi through," Cooke said.
The Biden administration's approach underscores the challenge facing the president as he struggles to balance two sometimes-competing goals: protecting the environment and bolstering the economy. President Joe Biden trumpets his green credentials, but industry lobbyists -- armed with warnings of higher costs -- are weakening some of his efforts.
Pressure from oil-industry allies has already complicated a push to curb pollution from the prolific Permian basin. And the stakes will only get higher as the administration begins writing sweeping regulations to throttle greenhouse gas emissions from power plants and passenger cars.
The Environmental Protection Agency's new rule on truck emissions, finalized in December, is meant to stifle smog-forming pollution from semi-trucks and other heavy-duty vehicles beginning with 2027 models. It's the first update of the limits in more than two decades.
Supporters praised the regulation as key to stemming respiratory illnesses stoked when nitrogen oxide spews out of tailpipes and reacts with sunlight to form ozone. EPA Administrator Michael Regan said the requirements would spur "air quality improvements across the United States," especially for the poor and communities of color overburdened by air pollution.
When engines come off the assembly line, they'll have to meet emissions limits more than 80% stronger than current standards. The provisions will drive a nearly 50% drop in nitrogen oxide emissions from heavy-duty trucks on the road in 2045, the EPA estimates. Additional on-road tests are supposed to ensure that pollution doesn't creep up when the engines are used in the real world.
But those on-road limits are relaxed between 77 degrees and 41 degrees. And at chillier temperatures, the real-world test data is scrapped altogether. That's a far cry from an earlier EPA proposal to ignore on-road performance only at 19.6 degrees and below. While the new rule still curbs pollution, the exemption has made it less effective.
"We're concerned that effectively it may mean that manufacturers have to put on less control technology" and "can let their emissions drift up," said Kim Heroy-Rogalski, chief of the California Air Resources Board's mobile source regulatory development branch.
In California alone, the change could translate to an extra ton of nitrogen oxide pollution per day in 2037, according to California Air Resources Board estimates -- roughly the equivalent of putting an additional 780,000 cars on the road, compared with what the rule would have achieved without the adjustment.
The exemption came at the behest of the Truck and Engine Manufacturers Association, a small-but-mighty trade group. Laboratory tests commissioned by the group used cold air blown over a sample engine to show that emissions increased below 77 degrees. Tightening pollution controls would require more heat, using more fuel and boosting greenhouse gas emissions, the association said.
Daimler Truck North America told the EPA that the proposed standards weren't feasible because cold air temperatures "directly affect the system's ability to comply." The EPA was urged to exclude test results achieved during higher temperatures.
When officials at the California Air Resources Board caught wind of the effort last fall, they pushed back. The state, long at the vanguard of U.S. environmental regulation, struggles to combat smog worsened by heavy-duty trucks hauling freight across the region.
The board was already doing real-world emissions monitoring on trucks in operation -- but in contrast to the industry-sponsored lab tests, California's data showed pollution controls still worked when temperatures dipped.
In the end, the EPA agreed with the manufacturers' arguments, calling the association's testing a key indicator of the standards' feasibility and concluding the results showed limits "should be numerically higher to account for real-world temperature effects."
The board's data came in too late to be considered in developing the final rule, the EPA said in an emailed statement. The agency stressed other requirements will help drive real-world performance.
The EPA's approach is unique. In Europe, real-world emissions aren't allowed to climb even when it's as cold as 19 degrees Fahrenheit, said Ray Minjares, director of the heavy-duty vehicles program at the International Council on Clean Transportation.
The manufacturers association argued that the temperature adjustment won't lead to a proportional increase in ozone because it doesn't form as easily in colder weather. California's on-road tests rely on older engine models, the industry group said. Daimler said the ambient temperature adjustments "reflect both the laws of physics and sound rulemaking."
California officials and environmental activists are pushing the Biden administration to to change course. Critics could file a lawsuit challenging the rule.
"We really think the EPA should reconsider that temperature adjustment," Heroy-Rogalski said. The California Air Resources Board is looking for ways "that we might have to encourage them to take another look at that."