Smog, or âground-level ozone,â as it is more wonkily called, occurs when emissions from combusting fossil fuels react with sunlight. Soot, or âparticulate matter,â is made up of tiny particles of chemicals, soil, smoke, dust, or allergens, in the form of gas or solids, that are carried in the air.
Arizona is a U.S. state with two senators in the United States Senate and nine representatives in the United States House of Representatives. Scroll down for a map of the districts.
Much of that growth has come in the past 40 years -- in 1970 there were less than two million people in Arizona. The population of Arizona is concentrated around Phoenix, the state capital, and Tucson, its second largest city. The largest county in Arizona by population is Maricopa County, which is home to 4.1 million of the state's 6.9 million people.