Why is indoor air quality an issue?

According to the National Safety Council, people, on average, spend about 90 percent of their time indoors. Of that 90 percent, 65 is spent at home, and to make matters worse, those who are most susceptible to indoor air pollution are the ones who are home the most: children, pregnant women, the elderly, and those with chronic illnesses. Children breathe in 50 percent more air per pound of bodyweight than adults do. EPA studies have found that pollutant levels inside can be two to five times higher than outdoors. After some activities, indoor air pollution levels can be 100 times higher than outdoors.