PHOENIX - A high-pollution advisory and no-burn day have been issued across Maricopa County and may extend through this weekend.
Arizona Department of Environmental Quality officials say anyone sensitive to pollution should avoid heavy physical activity outdoors Friday.
They also say people with respiratory problems including asthmatics should limit straining outdoor activity.
The ADEQ advisory predicts fine particulate matter in the area that is unhealthy for people sensitive to the air debris.
Authorities say that that type of particulate can come from combustion, including vehicles and wood burning.