Everything is bigger in Texas, including the number of chemical plants, refineries, and other industrial facilities. So when one of the worst storms in American history hit the heart of Texas’ petrochemical industry, it also triggered one of the biggest mass shutdowns the area has even seen. At least 25 plants have either shut down or experienced production issues due to Hurricane Harvey’s unprecedented severe weather and flooding, according to industry publication ICIS. But those closures are not only disrupting markets; they’re also causing enormous releases of toxic pollutants that pose a threat to human health.

Take Chevron Phillips Chemical plant in Sweeny, Texas. When it shut down due to Hurricane Harvey, it released into the atmosphere more than 100,000 pounds of carbon monoxide, 22,000 pounds of nitrogen oxide, 32,000 pounds of ethylene, and 11,000 pounds of propane, according to a report the company submitted to the Texas Commission on Environmental Quality (TCEQ). A couple thousand pounds of 1,3-butadiene, benzene, and butane were released as well. All of these releases were far more than what was legally allowed.

Chevron reported similarly huge amounts of air pollution above legal limits due to the shutdown of its chemical plant in Cedar Bayou. 28,000 pounds of benzene, a known carcinogen. 56,000 pounds of nitrogen oxide gases, which react to form smog and acid rain. From just one “miscellaneous” source at the facility, a combined 40,000 pounds of various chemicals were released—and that source had no legal authority to release anything at all.

Smaller emissions events were also submitted to TCEQ. In preparation for Harvey, the Equistar plant in Corpus Christi released 5,000 pounds of both carbon monoxide and ethylene. The shutdown of Chevron’s Pasadena Plastics Complex caused some excess releases, mostly of carbon monoxide and isobutane. Javelina Gas Processing facility went far above its relatively low pollution limits for its shutdown, reporting releases of 10,000 pounds of carbon monoxide and 4,000 pounds of butanes, among other things. One Pasadena refinery released a bit of particulate matter.

Between August 23—the day it became clear Harvey would threaten Texas—and August 29, industrial plants reported 74 excess air pollution release events to TCEQ, or nearly 60 percent more than the previous week. Those releases have so far totaled more than one million pounds of emissions above legal limits, according to Air Alliance Houston, an environmental nonprofit that crunched the numbers.