The bulk of your average household dust bunny consists of skin flakes, clothing fibers, outdoor dirt, and tiny shreds of houseplants and newspaper. But look closer and you'll see an even finer, gray dust. That's where the metals, pesticides, soot, and molds congregate; and for those nasty characters, houses are an excellent pollution preserve.
Outdoors, these things are at the mercy of sunlight and organisms in the soil that slowly break them apart. But once inside your home, they can snuggle into nooks and crannies and especially carpets, where they can linger indefinitely.
Children are at greatest risk for exposure to toxics in dust, because the average child can consume half a cup of powder-fine motes by age six just by sucking it off her thumb, or by eating dropped food. Recent studies suggest that babies who crawl through germy environments gain protection from allergies and asthma, so household sterility may not be a healthy goal. Fortunately, much of the nastiest stuff in dust is there because we bring it in. And that means we can stop a lot of it at the door.
No lead paint in your place? That's a start. But half the lead in your house may come from outdoors, often carried on your feet. Hot spots include roadsides where lead accumulated during the era of leaded gas, and the soil adjacent to a house whose exterior was once lead-painted. The solution is simple: Go shoeless indoors. And if you garden in dirt that may be contaminated, don't tromp through the house in dusty clothes.
Other metals, such as mercury from coal burners and chromium from metal finishing, also turn up in house dust, especially if there's an industrial source nearby. Unfortunately, all the dusting and vacuuming in the world won't solve the problem if there's a steady supply blowing in on the wind.
Smoke is a mixture of gases and little black particles that contains scads of noxious chemicals. While tobacco smoke is obviously harmful, even burned toast can produce soot that contains mutagens -- chemicals that tinker with your genes. Candles and incense are another source. Be very wary of candles with lead wire cores in their wicks.
Prevention is easy: Don't let your candles smoke. Some can be discouraged by trimming the wick every couple of hours. Others may need more oxygen than they can get in a jar. You can test an unburned wick for lead by smearing it across a blank sheet of paper -- lead leaves a smudge. And don't burn the toast.
And you thought the only mold you had to fear was the greenish one crawling across the bread. Increasingly, investigators of so-called "sick buildings" are discovering highly toxic strains of mold, particularly stachybotrys. The medical jury is still out on just how bad "stacky" spores are, but they've been blamed for things like memory loss, lung ailments, and a few infant deaths.
Molds love moisture, so ventilate, ventilate, ventilate. "Prevent-ilate" by cutting down on shower time, repairing leaks, and covering pots of boiling water. Air conditioners and dehumidifiers can help. For more on mold, see www.cdc.gov/nceh/airpollution/mold.
Most people use at least one pesticide indoors every year. In fact, some researchers estimate that 80 percent of our pesticide exposure occurs in our own
homes. How can that be? For the record: Rose powder is a pesticide. Roach killer is too. Moth balls are as well. For some alternatives, see www.epa.gov/iaq/pesticid.html.