You can’t control whether a relative smoked in the house you grew up in, whether the factory near your childhood home leached chemicals into the groundwater, or whether the air outside your apartment has fine particulates floating through it on any given afternoon. But oncologists —the doctors who spend their careers thinking about why people develop cancer—are clear about one thing: There’s a long list of exposures inside your home that you can actually do something about. “How we sleep , what