The EPA Let Companies Estimate Their Own Pollution Levels. The Real Emissions Are Far Worse.

This story was originally published by ProPublica .

For decades, noxious, cancer-causing gases poured from some of the nation’s largest industrial polluters, seeping invisibly from cracks in antiquated pipes or billowing out of smokestacks in plumes that choked the communities nearby.

And for decades, the Environmental Protection Agency tracked those emissions not by monitoring the air but by relying on a kind of honor system. Companies were allowed to estimate their chemical pollution using methods that even the EPA conceded were often unreliable.

In 2023, the EPA received irrefutable proof that these estimates were highly flawed. The agency had required 20 industrial facilities to temporarily install air monitors around their perimeters — known as fence-line monitoring — to see how ba