根据下面资料，回答31-35题 <br /> You've spent 90 percent of your life inside. What have you been breathing in that whole time? Conversations about pollution tend to focus on the outdoors—the exhaust from cars and buses, the contaminant smog that comes wheezing out of smokestacks and factories. But we're missing what's right in front of our noses, what we breathe in for most of our lives：indoor air.<br /> Indoor air pollution is "an area that's relatively unexplored compared to other fields in public health," says Dr. Joseph Allen, director of the Healthy Buildings Program at Harvard's Center for Health and the Global Environment. Despite the fact that indoor air is sometimes more polluted than outdoor air, "we haven't dedicated comparable resources to it." <br /> The issue of indoor air pollution was all but unspoken until the 1970s, when buildings started to get sealed with energy-conscious insulation. That's when so-called "sick building syndrome" started to pop up nationwide, with huge numbers of tenants complaining about sickness and discomfort. Their symptoms were mostly caused by indoor pollutants, particularly what scientists call volatile organic compounds, or VOCs. VOCs are especially harmful in indoor spaces because they easily evaporate；formaldehyde, for instance, boils at -2 degrees Fahrenheit, meaning it will sublimate in any indoor environment that isn't a deep freezer. <br /> VOCs are everywhere, in some of the most common materials and products of home and office—there is benzene in art supplies, formaldehyde comes in paint, perchloroethylene comes in fabric-, wood-, and shoe-cleaning products. They present a whole host of health threats, as do other types of indoor chemicals and pollutants, including the risk of causing cancer and "damage to the liver, kidneys, and central nervous system," according to the National Institutes of Health. <br /> WHAT CAN WE DO to protect ourselves? Allen says the solution may lie in the people responsible for making buildings, who have the power to control and monitor indoor air quality. And while the bigger solution may lie in ground-up renovations, everyone can help improve the air we breathe by looking for toxic chemicals on the labels on the products we buy, keeping up regular cleaning routines, and making sure to monitor and purify indoor air quality. <br /> "We must understand that the indoor environment influences your health," Allen says. "When people start thinking about where we spend our time and all that's around us, I think things will start to change." <br /> We can infer from the text that energy-conscious insulation________