A thick, smoky haze filled the North Texas skies on Oct. 19.
People called television stations and newspapers, including the Denton Record-Chronicle, as well as state and local officials asking about the unusual sight — and the putrid smell.
Some said the air smelled of chemicals, or burning plastic, or burning tires.
By midmorning, local officials took the extraordinary step of issuing an air quality alert for particulate matter, the extremely small, airborne particles that are able to get past the nose and into the lungs. Particulate matter can irritate the hearts and lungs and trigger health effects, such as asthma and heart attacks.
Television meteorologists reported a temperature inversion that Thursday in Dallas-Fort Worth. They said low winds and a warm layer of air about 5,000 feet up in the atmosphere kept the smoke from dispersing. A few suggested a controlled burn of grasslands near Midlothian and Mansfield could have been the source.
But no one really knew the cause. And it appears no one may ever know.
Officials at the Environmental Protection Agency in Dallas declined to answer questions, saying the Texas Commission on Environmental Quality was in charge.
The Texas Commission on Environmental Quality doesn’t consider the event “actionable” and is not investigating what caused the smog on Oct. 19, according to agency spokesman Andrew Keese.
Phoning it in
Some people knew to call the TCEQ that day to complain about the sights and smells, according to documents obtained by the Denton Record-Chronicle. An employee at a Whataburger in Arlington called after arriving at work that morning. The caller had stopped at Walmart on the way and noticed it smelled like tires burning. At the Whataburger near Interstate 20 and Collins Street, the employee said it still smelled like tires burning.
According to the complaint record, the caller looked for smoke or other possible source for the smell, but couldn’t see anything unusual.
Jane Lynn of Arlington called the TCEQ about 10 a.m., complaining that it smelled of burning chemicals or plastic outside.
"A thick, white haze covered the neighborhood and made it nearly impossible to be outdoors," Lynn said.
The TCEQ told her that without a known cause, they couldn’t investigate the problem, which frustrated her.
"There was a dead silence after it all blew away, and I want some answers," Lynn said.
The staff at the North Texas Council of Governments also noticed the haze and the smell, according to Chris Klaus, a program manager. Klaus heads the air quality programs for the council, a voluntary alliance of local governments that tackles regional issues.
Klaus saw that particulate levels were climbing along with the haze. After 9 a.m., the council staff decided the agency should issue an air quality alert, a first for them, Klaus said.
“It [the particulate] could be a health issue,” he said.
Alerts and monitors
The TCEQ takes the lead on air quality alerts. The agency usually issues air quality alerts for ozone, a more persistent problem in North Texas than particulate. But both ozone and particulate have levels regulated by federal law.
Federal regulations have both a short-term and long-term standard for particulate. The 24-hour standard, measured every hour and averaged for one day, is 150 micrograms per cubic meter of air. The annual standard, which is averaged over every hour of every day, is 12 micrograms.
At 9 a.m., when local officials issued the alert, the Arlington air quality monitor had reached a concentration of 56.4 micrograms.
At noon, at the peak of the haze, a Dallas monitor recorded concentrations of 176 micrograms and 141 micrograms. (The two numbers represent readings for two different sizes of particulate.) At noon, the Denton monitor also peaked at 41.8 micrograms of particulate.
State environmental officials did not issue an alert because particulate readings were not high enough, Keese said.
The agency’s seven monitors that tracked particulate that day averaged 12.5 to 22.2 micrograms. The haze was a nonevent in TCEQ’s view, Keese said.
The agency declined to comment on the council's decision to issue the alert for particulate.
“The air quality event referenced would not be considered unusual during ozone season,” Keese said in an email to the Record-Chronicle.
By the end of the day, ozone levels had increased, too. They rose high enough on Oct. 19 to change the game for 2017. Denton’s ozone monitor recorded its second-highest level of the year. And the year's average increased from 78 parts per billion to 79 ppb, making Denton's annual ozone readings the highest in the region again.
The federal limit for ozone is 70 ppb.
Satellite images show a bright line of smoke that begins shortly after dawn on Oct. 19. The images were obtained by the Record-Chronicle through an open records request to the National Oceanic and Atmospheric Administration. The plume appears to begin in Erath County, about 100 miles southwest of Arlington, according to Pinliang Dong, a geography professor at the University of North Texas.
Dong noted that subsequent satellite images show the line of smoke dispersing as it moves toward and through southern Tarrant and Dallas counties between 8:15 and 9:45 a.m.
“If the reported smell in the air occurred in the morning hours, my interpretation could be useful,” Dong wrote in an email.
Jim Schermbeck, a clean air advocate with the local nonprofit Downwinders at Risk, said he drove the freeways that day and noticed the plume seemed to run along the hills from the southwest in Midlothian toward the northeast to Dallas and Denton.
As the morning progressed, particulate readings at state monitors increased from the southwest to the northeast. The Midlothian monitor peaked at 37.9 micrograms at 8 a.m. The Arlington monitor peaked at 56.4 micrograms at 9 a.m. The Dallas monitor peaked at 141 micrograms and 176 micrograms at noon.
However, officials at both the Texas Forest Service and the Erath County Fire Department said they did not respond to any large fires that day.
Both Klaus and Schermbeck emailed state officials about the amount of time that goes by between the recording of air quality data and the time it is posted online — about two hours.
Schermbeck called the state's system antiquated, saying it doesn't enable officials to locate a source of pollution or predict how a plume is traveling to warn people in its path.
Other cities, such as Baltimore and Chicago, have air quality monitoring networks built with affordable technology that makes it possible to pinpoint pollution and even prevent future problems, Schermbeck said.
But the question whether state officials can predict or prevent another smoke-filled day like Oct. 19 is a non-starter for TCEQ, Keese said.
“This question is not relevant since there was not a specific incident that caused the event,” Keese wrote.
PEGGY HEINKEL-WOLFE can be reached at 940-566-6881.
FEATURED PHOTO: This still image from a NBC5 video shows smog over North Texas on Oct. 19. Courtesy photo/KXAS-TV (NBC5)