UPDATE: Walmart fire triggers air quality advisory, state warns of touching toxic debris

The fire at a Walmart Fulfillment Center west of Indianapolis Wednesday sent a huge plume of smoke billowing up into the air that could be seen for miles away.

In the aftermath of the fire, environmental and public officials in the area face a number of questions: How is this smoke impacting air quality? Are there toxins or other harmful substances in the smoke and debris? Is there any lingering threat to residents living or working in the path of the smoke plume?

Barely 24 hours later, with the charred remains of the giant warehouse in Plainfield still smoldering, it remains unclear what the fire, smoke and debris could mean for the environment and public health. Officials from state and federal agencies are working to find answers.

The fire began around noon Wednesday at the warehouse in Plainfield, about 15 miles west of downtown Indianapolis.

Walmart distribution center fire in Plainfield: What we know about massive Indiana blaze

The state operates air monitors in the downtown area, and the results from those monitors have remained largely normal in the last day, according to Nikos Zirogiannis, an assistant professor at Indiana University’s O’Neill School of Public and Environmental Affairs.

The city of Indianapolis said the fire was “front of mind” and they were following information from the Indiana Department of Environmental Management about air quality. Based on the data shared Thursday morning, the ozone and particulate matter levels were moderate.

By Thursday afternoon the city declared a Knozone Action Day. These are issued when ozone or particulate matter in the air rises above certain levels and may become unhealthy for sensitive individuals.

"IDEM notes that smoke is lingering in the area of Marion, Boone, Hendricks, and Hamilton counties, and that high particulate matter values have been monitored on the west side of Indianapolis," a city news release says.

IDEM issued its own release Thursday afternoon declaring an Air Quality Action Day. The department confirmed elevated levels of particulate matter PM2.5, which contains microscopic dust, soot and liquid that settles deep in the lungs and cannot be easily exhaled.

"Weather conditions will continue to spread the smoke to the northeast," IDEM's release says. "Conditions should improve overnight and Friday."

The action day is for Boone, Hamilton, Hendricks and Marion counties.

A network of resident-owned sensors also showed some potential impacts. Called PurpleAir, these are sensors owned by ordinary Hoosiers and installed at their homes.

A handful of sensors in the northwest part of Marion County showed rises in particulate matter that started yesterday afternoon and continued into the evening, though they have tapered off this morning.

Zirogiannis said the PurpleAir network is beneficial to give a sense of air quality in local neighborhoods, but does stress that the sensors are not as accurate as the agency monitors and do not have oversight. They also can be impacted by actions at the individual homes, such as if a homeowner started to grill near one of the sensors, he added.

In a fire like this, it’s particularly important to know what was burning.

If there were any sort of household chemicals or cleaners, that could mean toxic gasses and fumes were being released, Zirogiannis said. Those are toxins that would not be picked up by IDEM’s or PurpleAir’s monitors.

IDEM said it has Emergency Response staff on the scene. It is coordinating with the U.S. Environmental Protection agency for air quality testing, according to local officials.

Town of Plainfield spokeswoman Stephanie Singh said IDEM crews are on the ground working, and town officials are waiting to hear back about the results of the testing.

The state agency did not respond to questions about what tests it is doing or if it has detected any toxic substances. The Indiana Department of Homeland Security said IDEM expects to issue an update Thursday afternoon.

Homeland Security also is urging residents to avoid any ash and debris on their lawns. Local fire departments, including Bargersville Fire, echoed that notice to Hoosiers.

Bargersville Deputy Chief Mike Pruitt said on Twitter that “these materials can be very toxic” and could contain carcinogens, or cancer-causing toxins. Walmarts have everything from household chemicals to plastics, he said, and those items are mixing and burning together.

That unknown risk is why firefighters take precautions to protect their respiratory system and limit contact with these materials, Pruitt told IndyStar.

Ashes and debris traveled into Boone County, north of the fire. Officials at the county’s health department did not immediately respond to IndyStar inquiries, but a post to its Facebook page says, “It's all hands on deck for the Walmart Distribution Center fire. … Officials say that if you come across debris that you do not touch it for fear that it may be toxic.”

Hendricks County Health Department did not immediately respond to IndyStar inquiries. The Marion County Health Department said it did respond and provide support at the request of Hendricks County and its Hazmat team is monitoring for any effects in Marion County.

It is unclear at this time how debris and potential air quality impacts will be addressed and who will be responsible.

This story will be updated.

Call IndyStar reporter Sarah Bowman at 317-444-6129 or email at sarah.bowman@indystar.com. Follow her on Twitter and Facebook: @IndyStarSarah. Connect with IndyStar’s environmental reporters: Join The Scrub on Facebook.

IndyStar's environmental reporting project is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.

This article originally appeared on Indianapolis Star: UPDATE: Walmart fire causes air quality advisory for Central Indiana