Smoke from Ferguson fire causing air quality to reach danger level

Smoke from the Ferguson Fire caused air quality in Fresno to reach the danger zone for a few hours Tuesday.

Early Tuesday, soot from the fire caused one measure of air quality to reach Level 5, meaning “No outdoor activity. All activties should be moved indoors,” according to advice from the San Joaquin Air Pollution Control District.

Fine particulate matter known as PM 2.5, which can get into the bloodstream via breathing and cause health problems, exceeded 75 micrograms per cubic meter for four one-hour periods from midnight to 4 a.m. Tuesday.

The high reading was registered by the central Fresno air monitor.

The measure then dropped to a lower level at which sensitive individuals should stay indoors and people should exercise indoors or limit vigorous activity outdoors. After noon, the risk level fell to safer Levels 3 and 2.

Also Tuesday, the Environmental Protection Agency issued an Air Quality Index map showing bad air coming to Fresno from the Ferguson Fire early Tuesday.

Although the central San Joaquin Valley is a federal non-attainment area for air pollution, high PM 2.5 values caused by wildfire emissions do not count against the region, said Jaime Holt, spokeswoman for the San Joaquin Valley Air Pollution Control District.

The EPA deems wildland fires to be “exceptional events,” she said.

Meanwhile, the Valley has been experiencing high ozone numbers at air monitoring stations most of the month, according to preliminary data from the California Air Resources Board. Ozone is a precursor to smog.

High ozone numbers can be attributed to wildfires, but the numbers must be analyzed to figure out what caused them, as summer is the typical ozone season, Holt said.

“It is not as cut and dry as the high PM 2.5 readings,” she said.

On July 25, the San Joaquin Valley Air Pollution Control District issued a “health cautionary statement” about smoke from the Ferguson Fire in Mariposa County and other fires.

“Smoke from wildfires produces particulate matter which can trigger asthma attacks, aggravate chronic heart and lung diseases, and increase the risk of heart attack and stroke,” the district said. “Where conditions warrant, people with heart or lung disease should follow their doctors’ advice. … Anyone being exposed to poor air quality or wildfire smoke should move inside to an air-conditioned environment.”

This story was originally published July 31, 2018 at 6:28 PM.