In the early hours of August 22, 2020, Hurricane Laura was still just a tropical depression off the coast of the Leeward Islands in the Caribbean.

But effects from the monstrous storm, which would ultimately take at least 81 lives, were already being felt on the U.S. Gulf Coast.

As rain poured down on the Sweeny refinery in Old Ocean, Texas, that afternoon, two processing units failed, releasing nearly 1,400 pounds of sulfur dioxide, which can cause trouble breathing, and other chemicals.

Over the next few days, Laura siphoned up moisture from the warm waters of the Gulf of Mexico and transformed into a Category 1 hurricane.

In Texas, chemical plants began shutting down, hurriedly burning off unprocessed chemicals and releasing vast amounts of pollution in anticipation of the storm making landfall.

On August 24, Motiva’s Port Arthur refinery released 36,000 pounds of sulfur dioxide, hydrogen sulfide, and other noxious pollutants.

The next morning, Motiva began purging chemicals its plant had been processing, emitting nearly 48,000 pounds of carbon monoxide and propylene, among other pollutants.

The following day, a Phillips 66 refinery in southwest Louisiana shut down, releasing more than 1,900 pounds of sulfur dioxide.

Then, as gale-force winds swept through coastal communities and the relentless rain poured down, the chemical facilities increasingly malfunctioned.

On August 27, an overflow container at Motiva’s Port Arthur refinery flooded, causing it to spew over 1,700 pounds of pollutants.

Across the border in Louisiana, a chemical plant caught fire.

In Texas alone, Hurricane Laura resulted in at least an additional 680,000 pounds of pollution — almost as much as the toxic load carried on the train that derailed in East Palestine, Ohio, earlier this year.

These so-called “excess emissions” — the term of art for intentional and at times inevitable pollution beyond permitted levels — don’t just happen during hurricanes. From petrochemical refineries on the Gulf Coast to oil and gas wells in West Texas, hundreds of polluting facilities routinely emit hundreds of millions more pounds of chemicals into the air than their permits stipulate. The reasons are many: when a plant unexpectedly loses power, or when a customer is suddenly unable to receive the natural gas extracted at a well, or when a valve or pump or any other piece of complex machinery malfunctions.

The resulting pollution contains nitrogen oxides, sulfur oxides, and a slew of carcinogenic chemicals. Companies claim that these emissions are unavoidable. When faced with malfunctions or natural disasters, facilities have no option but to quickly shut down, which forces them to burn off the chemicals they’re processing. It is a necessary evil — or so goes the claim.

Read the full article about excess emissions by Naveena Sadasivam, Clayton Aldern, Jessie Blaeser and Chad Small at Grist.