When the television is on, it generates heat; similarly, when someone sits on a sofa, her body heat is transferred into the cushions. Tiny amounts of flame-retardants incorporated in these common household furnishings to nullify the flammable petrochemical polymers they're made of (substances like plastic and polyurethane) begin to leach out. The flame-retardant chemicals attach themselves to dust particles on the floor or pieces of furniture, says Heather Stapleton, an assistant professor of environmental chemistry at the Nicholas School of the Environment.
Stapleton is studying how these chemicals end up entering the human body. She will soon begin testing children—who spend more time on the floor and are more apt to put objects in their mouths—to see whether by ingesting more dust, they also are ingesting more of the chemicals.
Dust, which Stapleton describes as a catchall definition for a host of solid particles smaller than 1 millimeter in diameter, is itself an elusive topic of study. Its composition differs from region to region and even from house to house, making it difficult for researchers to draw conclusions about something as seemingly simple as how chemicals stick to it. (The microscopic shot of household dust shown here includes fabric fibers and fungal spores.)