Pima County’s air quality has reached unhealthful levels, thanks to high winds and blowing dust.
For large particles, a monitor near Grant Road and First Avenue was slowly climbing in the morning, and the air-quality index hit 103 at 2 p.m., after hitting 101 at 1 p.m., 95 at 10 a.m. and 97 at 11 a.m.
At a level of 101, the air is rated unhealthy for sensitive groups such as asthmatics and others with heart or lung diseases, as well as seniors and the very young. From 51 to 100, the air is rated moderate, meaning it’s OK for average citizens to breathe, but that people with heart and lung diseases should try to limit their outdoor exertion.
“At this point, we're not saying not to go outside. We're saying that when you are outside you should limit your exertion levels,” said Beth Gorman, a Pima County Department of Environmental Quality program manager. “If people are supersensitive, they may want to restrict their exposure to outside air.”
Shortly after 11:30 a.m. today, the county DEQ issued an air pollution advisory because of the high readings. The particles are uprooted by high winds from their natural homes in farms, mines, dirt roads, vacant lots and disturbed areas.
Particulate matter is made of tiny specks of soot, dust, and aerosols that are suspended in the air.
The advisory was issued because the air quality index readings keep ticking up, pushing closer toward being unhealthy for sensitive groups, German said.
“As I’m looking out the window, the visibility seems to be worse than it was this morning,” German said just after noon.
On the positive side, the actual dust concentrations in the county air monitor at Grant and First — the one with the highest readings in the county monitoring network — have been declining all morning, after peaking around midnight, she said.
The reason the AQI keeps rising is that it represents an average of 24 hours of air quality readings. As low concentrations from Thursday morning and early afternoon fall out of the index as this day proceeds, the index level is rising because the 24 hour average grows -- even as the hourly concentration readings are now dropping.
“The good news is that we’re not adding to the problem now,” German said. “But there’s still a lot of particulate dust in the air, and the particles are so small that they will remain airborne for a little while before it settles out.”
It’s now a race against time to see if the AQI reading reaches 101 before the hourly particulate levels drop enough to make a 101 reading impossible, German said.
Contact reporter Tony Davis at firstname.lastname@example.org or 806-7746.