Over 2,000 code orange air quality alerts were issued across the U.S. in 2011 alone, a recent report by the National Resources Defense Council (NRDC) found. The surge in code orange conditions—which warn that air quality is unhealthy for those with lung diseases, the elderly, and children—means more people remaining indoors as a health precaution.
“Too many Americans are breathing unhealthy air this year," says the NRDC's John Walke. "Orange is the dividing line between whether people play outside or decide to stay indoors that day."
The Air Quality Index, which is determined by EPA assessments of harmful pollutant concentrations in the air, is a color-coded system of six levels. The levels and their meanings are: green — healthy; yellow — moderate; orange — unhealthy for people with respiratory conditions, seniors and the young; red — unhealthy for everyone; purple — very unhealthy, emergency conditions; maroon — hazardous.