The Arizona Department of Environmental Quality issued a PM-10 health watch for Thursday.
A health watch is issued when unhealthy air quality levels may approach federal health standards.
PM-10 stands for particulate matter measuring 10 microns or less. Arizona's particulate matter season typically starts with cooling temperatures. Particulate matter is created from either combustion (from car, industry and woodburning) or dust stirred in the air.
During a health watch, residents are encouraged to carpool and limit or keep from burning wood in fireplaces or outdoor fire pits.
For information on transportation alternatives, visit Valley Metro: www.ValleyMetro.org or call (602) 253-5000.