Thread by @albiewxdude

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Since I do air quality consulting for a living, I have been following this incident at the ITC site in Deer Park for the last few days. Before I state why I think this is a really big story that isn’t getting nearly enough press

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(yes, I know there’s been a lot already), let me give a little bit of background about my expertise. I am a meteorologist who specializes in analyzing the dispersion of air pollutants in the atmosphere via analysis of air quality monitoring data and air quality

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modeling data. I have over a decade of experience doing this kind of work and have worked for the Texas Commission on Environmental Quality (TCEQ) and for private sector consulting firms.

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When this event started several days ago, it caught the public’s attention in a hurry because of the huge plume of smoke that resulted from the materials in the tanks being combusted by fire. While this was an onerous sight, no air quality monitors in the area

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were detecting pollution concentrations above acceptable levels. This is because as these vapors were being burned, the heat caused the pollution to increase in buoyancy and rise in the atmosphere. This allowed the pollution quite a bit of time to disperse above

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the ground before hitting ground level and affecting people. By the time this happened, dispersion was sufficient such that no monitors detected any air quality issues.

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The fire lasted for three days and was extinguished on Wednesday. Once the fire was extinguished, the problem that was visible to the public was solved, but a much bigger problem was manifesting. Vapors of toxic materials were still escaping from the site, but

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they were no longer being burned. This lack of burning resulted in the pollutants not being destroyed by combustion and not being well-dispersed. Raw vapors were being released virtually at ground level and began to directly affect the surrounding area.

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The pollutant of biggest concern is benzene for two reasons. First, benzene is present in all of the materials that were stored in the affected tanks at the ITC site. Second, benzene is an extremely toxic chemical, and the fact that exposure causes cancer is

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well-known. The TCEQ has an exemplary Toxicology Division, and part of their job is to determine what are called Air Monitoring Comparison Values (AMCVs) for toxic pollutants such as benzene. Hourly monitored concentrations of air pollutants that are above an

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hourly AMCV are considered hazardous to human health. The hourly AMCV for benzene is 180 parts per billion (ppb). On the morning of March 21, 2019, the Houston Deer Park #2 monitor recorded a benzene level of 191 ppb.

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This may not sound that severe, but this also requires some important context. The image below shows the location of the ITC site (upper green point) and the location of the Houston Deer Park #2 monitor (lower green point). The distance between the ITC site and

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the monitor is approximately 5.6 miles. Since the uncombusted pollutant vapors had very little dispersion at all, the concentration of benzene at ground level would increase with decreased distance to the site. Since hazardous levels of benzene were able to make

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it more than 5 miles away from the site to a monitor southwest of the facility, it can be reasonably concluded that a large part of Deer Park (the area between the site and the monitor) experienced ground level concentrations of benzene much higher than the 191 ppb

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detected by the monitor. There is no way to know how much higher, unfortunately, since there are no other benzene monitors between the ITC site and the Houston Deer Park #2 monitor. However, the fact that hazardous levels of benzene were able to cover such a

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large area is extremely concerning. This is a much greater public health problem than the fire ever was, but it’s not getting nearly enough press due to the fact that this problem is not visible.