Pollutants—such as smoke from tobacco, burning wood, and cooking; gases from cleaning products and building materials; dust mites; mold; and pet dander—all contribute to an unhealthy indoor environment that has ill effects on human health. Over the past year, we’ve seen these hazardous conditions compounded by the presence of wildfires in California and the Midwest.

Fine particles 10 micrometers in diameter or smaller, including those found in dust and smoke, are especially a concern because they can make their way deep into the lungs. Breathing in particles for just hours or days is enough to aggravate lungs and cause asthma attacks, and has been linked to heart attacks in people with heart disease. According to the EPA, long-term exposure to high particle levels is linked to bronchitis, reduced lung function, and premature death. 

Volatile organic compounds (VOCs), including formaldehyde, that are released into the air from adhesives, paints, and cleaning products can cause nose, throat, and eye irritation; headaches; nausea; and damage to the liver, kidney, and nervous system. Some gases, such as radon, cause lung cancer and death.