First came the water; then came the fire.

Explosions and flames erupted into the air at a chemical plant in Crosby very early Thursday morning. Floodwaters had knocked out the cooling system needed to prevent organic peroxides from breaking down, and also blocked any path for workers to get back to the site and prevent the disaster.

Now the surrounding residents, living 25 miles northeast of downtown Houston, have been instructed to shut their doors and windows, turn off air conditioners and do everything possible to avoid breathing in the acrid smoke and fumes pouring out of the plant owned by Arkema Inc.

So what, exactly, is in the air?

That's a very good question.

As Chronicle reporters Mark Collette and Matt Dempsey revealed in their 2016 "Chemical Breakdown" series, more than 2,500 facilities throughout the Greater Houston region contain stockpiles of explosive or toxic materials. Federal safety inspections are rare and our state government helps corporations conceal contents. Politicians, industry leaders and their lobbyists have been working for years to keep Texans ignorant about the chemicals and toxins that dot our landscape.

Rich Rowe, Arkema's CEO, is just another example. He refused to make public the plant's chemical inventory or its federally mandated risk management plan, the Chronicle reported.

Exposure to the Arkema fire has sent 15 sheriff's deputies to the hospital as of this writing, yet the company still won't explain the specific sort of adverse health effects that people should expect from the emissions. The company also couldn't answer pointed question by Dempsey about why volatile materials weren't neutralized before workers fled the site.

A known carcinogen - polycyclic aromatic hydrocarbons - has already been detected in the smoke, according to Neil Carman, clean air director for the Sierra Club's Lone Star Chapter.

Who knows how bad things really are?

All across Houston's chemical complexes, as Hurricane Harvey bore down, odors and flames settled into the cloud-filled sky. At least 32 air emission events were reported with the Texas Commission for Environmental Quality, and at least 20 chemical or gas leaks have been listed by the Coast Guard's National Response Center.

The National Response Center's log of spills and emissions, Chronicle's business columnist Chris Tomlinson noted, hasn't been updated since Sunday.

In 2013, 15 people died and more than 160 others were left injured after the West Chemical and Fertilizer Company erupted in a massive explosion. Dozens of homes were destroyed but apparently no lessons were learned. A 2016 report conducted by the U.S. Chemical Safety Board found that Texas had failed to respond to the disaster with laws or regulations that would keep Texans safe from a similar sad fate.

How many more people have to end up in the hospital - or the morgue - before our politicians treat chemical threats with a sense of deadly seriousness?

Harvey was an act of God.

The disaster in Crosby is purely man-made.

Gov. Greg Abbott has the ability to call a special session and demand that the Legislature pass laws mandating transparency, safety and land use rules that will prevent future disasters. Until then, we look to Harris County District Attorney Kim Ogg, County Attorney Vince Ryan and federal prosecutors to investigate Arkema and other companies with serious scrutiny.

The lights may finally be coming on at homes across the Gulf Coast, but we still remain in the dark about dangerous chemicals.