Washington science writer Seth Borenstein knew the U.S. Environmental Protection Agency was not going to notify anyone when it posted new data on the nation’s air quality for 2018. But he knew where it would be posted, and knowing it would be newsworthy, he just kept checking.

President Donald Trump had been saying that U.S. air quality had never been better, and that it had improved while he was president. Trump’s administration was using that rationale, in part, to replace an Obama-era clean-air rule with a new regulation that was friendlier to coal-fired power plants, and that is almost assured, experts say, to lead to worse air quality and more deaths.

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The Utah State Capitol in Salt Lake City is shown during a clear day, Dec. 13, 2018, and during an atmospheric inversion four days later. Inversions trap tailpipe and other emissions in the bowl-shaped mountain basins, creating a murky haze that engulfs the capital. Federal data shows U.S. air quality worsening in the past two years, but scientists say it is too early to see the effects of environmental policy by the Trump administration. They say, however, that looser restrictions will almost certainly reverse the gains made in recent decades.

AP Photo / Rick Bowmer

When the air quality data finally showed up, Borenstein teamed with New York-based Health and Science data journalist Nicky Forster to evaluate the data, put it in context and run it by scientists to make sure we fully understood it. It appeared to show that air quality was, for the second year in a row, worse than it had been earlier in the decade.

But Forster also found errors in the posted data, which he pointed out to EPA. AP couldn’t run the story based on numbers we knew were wrong, but the EPA, while admitting the errors, did not initially say when or if it would fix them. Forster and Borenstein pressed the agency persistently over a period of four weeks until finally they fixed the mistakes: The EPA had initially undercounted the number of extremely hazardous air days.

Their persistence made AP the first to report that the annual number of days of poor air quality in the U.S. had increased for the second year in a row. After decades of improvement, U.S. air quality was starting to deteriorate.

The story ran on the eve of the EPA’s announcement of its new regulation, undermining the rationale for the new standards with the government’s own numbers. Trump’s new rule, experts told the AP, could turn what is so far a modest backslide into a deadly trend. “There is zero reason to expect any other outcome,” one expert said. The story appeared on several front pages, it was featured by Axios and MSNBC, and it attracted more than 200,000 Facebook engagements.

For diligent reporting and sophisticated analysis to hold a federal agency accountable for its data and regulatory policy, Borenstein and Forster earn this week’s Best of the States award.