Indoor levels of pollutants may be two to five times higher than outdoor levels. So even in cold weather, keep a window cracked, at least in the bedroom. Also run exhaust fans in high-humidity areas like bathrooms and the kitchen.

Choose natural cleaners; many mass-market products contain alkylphenols, ammonia, and other toxins that can trigger asthma, irritate the lungs and throat, and cause other health problems. Avoid candles or air fresheners with synthetic fragrances that contain harmful phthalates; soy candles with natural fragrances are more pleasant, anyway.

Consider replacing wall-to-wall carpeting with area rugs, and buy natural, untreated shower curtains and flooring instead of phthalate-emitting vinyl. If you don’t already have them, install carbon monoxide detectors and air purifiers. Last but hardly least, don’t let anyone smoke in your home.

To learn more, contact

• American Lung Association, www.lungusa.org
• EPA Indoor Air Quality, www.epa.gov/iaq
• Healthy Indoor Air for America’s Homes, www.healthyindoorair.org
• Safer Products Project,www.safer-products.org