Last year, the U.S. Embassy installed an air monitor on the roof of one of its buildings, and every hour it posts the results to a Twitter feed, with a score ranging from 1, which is the cleanest air, to 500, the dirtiest.

NEWYORKER: Green Giant

The EPA said it is working with Federal Emergency Management Agency and the Texas Committee on Environmental Quality to monitor air quality in the area.

WSJ: Fertilizer-Storage Risk Is Often Overlooked

The pilots said there was "a concentrated period of discussion where they did not monitor the airplane or calls" from air traffic control, though both said they heard conversation on the radio, the report said.

CNN: Report: Stray jet's pilots were on laptops