Air pollution, chemical and gas spills, dirty floodwater: Harvey is posing a unique threat to public health and an incredible challenge for the regional EPA.Harvey Has Morphed into a multi-pronged environmental disaster.

At first, it was just another thing to worry about. Hurricane Harvey was headed straight toward the heart of America’s petrochemical industry, where dozens of refineries and chemical plants sit next to vulnerable communities. There were forecasts of biblical rainfall, which experts predicted could flood facilities and cause accidental toxic substance releases, or worse, explosions. If multiple plants shut down at once, there could be huge emissions of harmful air pollutants. And if too much rain fell on the region’s Superfund sites, they could overflow, threatening human health.

It’s been nearly a week since Harvey first made landfall in Texas, and all of these things have happened. In the most high-profile case, a flooded chemical plant east of Houston burst into blast smoke twice, leaking chemicals and sending 15 people to the hospital. Federal Emergency Management Agency administrator Brock Long is calling the plume “incredibly dangerous,” noting that the organic peroxides at the facility pose threats to human health. Residents living in a 1.5-mile radius around the plant were ordered to evacuate.

But this is far from the only pollution event that has resulted from Harvey, and arguably not the most dangerous. More than one million pounds of toxic air pollutants have spewed into the region’s atmosphere due to mass refinery and chemical plant shutdowns, with more pollution events expected as the plants start to back up. Drinking water across southeast Texas is also “going to be contaminated,” infectious disease specialist Rick Watkins told the Guardian, because of the disruption of sewage systems, which will leak into floodwater. According to Newsweek, “drinking water has [already] come into contact with dirty floodwater.” Superfund sites, of which there are at least a dozen in Harris County, continue to threaten contamination of floodwater as well.

Other spills are happening too. Rainfall caused a 6.3-million-gallon gas tank to tip over and leak “an unspecified amount” of fuel at a Kinder Morgan facility in Pasadena. On Wednesday, the Sierra Club released a long list of issues reported at petrochemical facilities across the region. More are likely on the way.

These combined threats pose a truly unprecedented challenge for the regional office of the Environmental Protection Agency that covers southeast Texas. “I can tell you, there was nothing even remotely like this during Sandy,” said Judith Enck, the former EPA Region 2 administrator who handled the environmental response to that historic 2012 storm. “We had some refineries in New Jersey that were impacted, but nothing like this.”

Fortunately, the regional EPA office covering Houston and the surrounding areas appears to recognize the magnitude of the challenge. On Wednesday, EPA’s Region 6 office activated the National Incident Management Team, said David Gray, the office’s acting deputy regional administrator. That team consists of on-scene disaster response coordinators from other regional EPA offices across the country to handle the multiple threats. And though President Donald Trump has not appointed a Region 6 administrator, the acting administrator, Sam Coleman, was in charge of EPA’s response to Hurricane Katrina. “Our team here in Region 6 has a lot of experience over the years in responding to emergencies,” Gray said in an email.

Specifically, Gray said EPA officials have inspected two Superfund sites near Corpus Christi and have visited two wastewater and drinking water systems that may be contaminated. (Gray did not specify which ones.) He said aerial assessment aircrafts are conducting reconnaissance over the impacted area. And he said the regional office is coordinating with FEMA and EPA’s D.C. headquarters. “Administrator [Scott] Pruitt is in regular contact with EPA staff across the agency who are part of this hurricane response effort,” Gray said.

It is far too early to assess the effectiveness of the EPA’s response—and too early to say what the human health effects will be. While the Arkema chemical plant situation was drawing significant attention from the media on Thursday, it is not the biggest threat to public health, according to Dan Cohan, an environmental engineering professor at Rice University who specializes in air quality management. That honor will likely go either to contaminated drinking water or to the air pollution coming from the many petrochemical facility shutdowns and startups.

“I think the shutdowns and startups and other exceptional event releases are likely more important (though less dramatic and visible),” Cohan said. “They’re likely to release far more pollution overall, and the startups coming during weather when the pollution could more easily impact air quality.” Mass shutdowns of petrochemical facilities have already released thousands of pounds of carcinogenic compounds into the atmosphere, but the wind and rain from the hurricane likely dissipated the emissions. Now, as the rain and winds clear, multiple petrochemical facilities will be starting up at the same time. Startups are huge emissions events, and many will likely be happening in unison.

The vast majority of these plants are located in the Houston area, posing a health risk to the millions of people who live there. Most at risk, however, are the communities that live directly next to the facilities—communities that are disproportionately low-income and minority. In a statement issued via the Sierra Club, local Houston environmental justice organizer Bryan Parras said the risk these communities face is “terrifying,” particularly because the state’s air quality monitors are down. “The only way we can really know what’s happening is when we see it or smell it,” he said.

The uncertainty that comes with this multi-pronged pollution risk will be a new feeling for many in Houston and the surrounding area, but not for Parras or the people who live in the city’s East End. “The environmental crimes against my community and thousands more like it have been happening for decades, and superstorms like Harvey only heighten the threats we face,” he said. Perhaps now that the threat has ballooned into a region-wide crisis, those in charge of preventing these disasters will start to pay attention.