We tend to think of air pollution as something outside -- smog, ozone, or haze hanging in the air, especially in summer. But the truth is, the air inside homes, offices, and other buildings can be more polluted than the air outside. The air inside your home may be polluted by lead (in house dust), formaldehyde, fire-retardants, radon, even volatile chemicals from fragrances used in conventional cleaners. Some pollutants are tracked into the home. Some arrive via a new mattress or furniture, carpet cleaners, or a coat of paint on the walls.
In that mix, you'll also find microscopic dust mites -- a major allergen -- plus mold and heaps of pet dander, says David Lang, MD, head of Allergy/Immunology at the Cleveland Clinic. "Even if you don't have pets, you've probably got pet dander," he tells WebMD. "It's become what we call a community allergen. Pet owners carry it around on their clothes and shed it throughout the day. You can't get away from it."
Children, people with asthma, and the elderly may be especially sensitive to indoor pollutants, but other effects on health may appear years later, after repeated exposure.
Indoor allergens and irritants have become much more important in recent decades because we're spending more time indoors, Lang says. And because modern homes are airtight, these irritants can't easily escape. "We're all exposed to a greater degree than we were three or four decades ago," he says.