“Excess” Emissions From Industrial Shutdowns and Startups Are Increasing Air Pollution

When Hurricane Harvey struck the Texas coast in August 2017, many industrial facilities had to shut down their operations before the storm arrived and restart once rainfall and flooding had subsided.

These shutdowns and startups, as well as accidents caused by the hurricane, led to a significant release of air pollutants. Over a period of about two weeks, data we compiled from the Texas’ Air Emission Event Report Database indicates these sites released 2,000 tons of sulfur dioxide, carbon monoxide, nitrogen oxides, volatile organic compounds and other pollutants.

These types of emissions that result from startups, shutdowns or malfunctions are often referred to as “excess” or “upset” emissions and are particularly pronounced during times of natural disasters, as was the case with Hurricane Harvey.

However, as we document in a newly published study in the journal Environmental Science & Technology, they also occur regularly during the routine operation of many industrial facilities, sometimes in large quantities. And, even if unintended or unavoidable, the pollutants released during these events are in violation of the U.S. Clean Air Act (CAA).

With the EPA now revisiting the rules regarding these air toxics, our study shows how significant they are to public health — and how historically they have not been systematically tracked across the country or regulated comprehensively.

Excess Emissions in Texas

Our study examines the occurrence of excess emissions in industrial facilities in Texas over the period from 2002 to 2016. We focused on Texas because, unlike nearly all other states, it has established comprehensive reporting requirements. The state collects data on so-called hazardous air pollutants that cause harm to people exposed to them, such as benzene, as well as substances called criteria pollutants, such as nitrogen oxides that contribute to the formation of ozone.

As a general rule, states set limits to industrial air emissions based on provisions in their State…

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