Tropical Storm Harvey has caused unprecedented flooding in southeast Texas — but other dangerous environmental disasters could be on their way, including the leakage of chemicals that could explode or harm people.

Making landfall as a Category 4 hurricane, Harvey hit right into the heart of the state’s petrochemical industry. Several plants shut down to brace for the bad weather, but refineries and chemical plants have still been damaged.

Here’s a list of some of the most dangerous environmental threats currently developing in Texas:

Arkema’s chemical plant in Crosby

All residents within 1.5 miles of the plant were evacuated today, as chemicals could catch fire and explode, according to Reuters. The plant has been hit by over 40 inches of rain and was heavily flooded. That caused back-up electricity generators to stop working. These generators are key for keeping chemicals at low temperatures. If the chemicals heat up, they can catch fire or explode — and the plant has no way of preventing this from happening right now.

ExxonMobil’s refineries

The roof of a tank at the company’s Baytown oil refinery, the second-largest in the US, sank because of the heavy rains, causing the release of hazardous pollutants, according to The Washington Post. At a second petrochemical refinery in Beaumont, the storm damaged a piece of equipment that captures and burns sulfur dioxide, releasing over 1,300 pounds of the chemical. SO2 can cause respiratory problems in people, particularly in children, the elderly, and those with asthma. High concentrations of the chemical can also harm trees and cause acid rain.

Chevron Phillips chemical plant in Sweeny

When the plant was shut down during Harvey, it released 100,000 pounds of carbon monoxide, 22,000 pounds of nitrogen oxide, 32,000 pounds of ethylene, 11,000 pounds of propane, and a couple thousand pounds of 1,3-butadiene, benzene, and butane, according to The New Republic. These chemicals can harm human health, as well as the environment. Nitrogen oxide, for example, can cause respiratory problems. Benzene disrupts how cells work, and in the long-term, can damage the immune system and cause cancer.

Chevron chemical plant in Cedar Bayou

This plant was also shut down during Harvey, and it released huge amounts of chemicals, including 28,000 pounds of benzene and 56,000 pounds of nitrogen oxide gases, according to The New Republic.

Toxic Superfund sites

Harris County, where Houston is located, has at least a dozen federal Superfund sites — contaminated areas that the government is trying to clean. The heavy flooding could spill chemicals from these heavily polluted sites into the water, and deposit them where people live. It could even contaminate well water that people drink. Some of these sites contain oily sludge and pollutants like perchloroethylene and chlorinated hydrocarbons that are dangerous for people, according to The Washington Post. Before Harvey hit, the Texas Commission on Environmental Quality (TCEQ) secured the sites, shutting down systems and removing chemical wastes, The Post reports.

Resident who have environmental concerns can report them to the TCEQ by calling the complaint hotline, 1-888-777-3186, or by going online. The TCEQ also recommends residents check its hurricane response page, where people can check boil water notices, for instance. Harris County residents should contact Harris County Pollution Control Services at 713-920-2831 to report pollution concerns. City of Houston residents should contact 713-837-0311 or 311, according to Matthew Tresaugue, the manager of Houston Air Quality Media Initiative at the Environmental Defense Fund.