Scientific American – Here’s how to read the Air Quality Index and protect yourself from unhealthy air – “The color-coded Air Quality Index categories you’ll find on the Environmental Protection Agency’s AirNow website rank air quality on a 500-point scale and are meant to give the public an easy way to understand the health effects of the air around them daily. The lowest numbers on the scale indicate healthy air, and the high end is hazardous…The Air Quality Index considers five measurements of air pollution: ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide and nitrogen dioxide. These pollutants have health impacts, typically involving irritation and inflammation of the respiratory system, which can, in turn, contribute to the development of conditions such as asthma and heart disease…”