Mobile monitoring for an airborne carcinogen in Louisiana's 'Cancer Alley'

In 2016, the U.S. Environmental Protection Agency (EPA) classified ethylene oxide as carcinogenic to humans, particularly when it is inhaled. Despite significant concern over chronic ethylene oxide exposure for people living between Baton Rouge and New Orleans, there are no published reports of ambient concentrations of the carcinogen that aren't derived from industry self-reported emissions data. So, Peter DeCarlo and colleagues proposed measuring the levels of this gas using optical instruments that quickly measure airborne chemicals and provide results in real time.

They used a mobile monitoring system with equipment mounted on a small truck or van. These mobile laboratories drove a fixed route along a heavily industrialized portion of the corridor.

• One small truck carried a tunable infrared laser direction absorption spectrometer, which measured ambient ethylene oxide in the surrounding air.
• The van carried a cavity ringdown spectrometer to detect downwind of petrochemical sites contaminant plumes, i.e., mixtures of ethylene oxide and other chemicals, which indicate the type of facility that emitted them.

DeCarlo and the team completed 23 130-mile laps with their mobile monitoring vans from January to February 2023. All of the ethylene oxide measurements were higher than EPA estimates, which were gleaned from industry-reported emissions. Specifically, the researchers' ambient air measurements revealed that most of the region had ethylene oxide levels that correspond to risk levels above EPA's acceptable upper limit. A few locations had contaminant concentrations that represent potentially serious health risks for facility workers. And the team's second van, with the cavity ringdown spectrometer, identified chemical plumes up to 7 miles from their likely sources, which are beyond the 6-mile distance of "fenceline communities." EPA defines fenceline communities as those where people live close enough to highly polluting facilities that they could be directly affected by the emissions of operation.

The researchers hope that this demonstration of a mobile monitoring system helps increase accurate measurements of hazardous air pollution in an area densely populated with ethylene oxide emitters. Their work also highlights important issues related to current detection and reporting methods and associated health impacts on people living near potential pollution sources.

The authors acknowledge funding from Bloomberg Philanthropies and the National Institute of Environmental Health Sciences.

Some coauthors are employed at Aerodyne Research, Inc., which provided a mobile laboratory and field sampling equipment. Some coauthors are employed at Picarro, Inc. which manufactures one of the instruments used in the study.