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The fact that DDT is still in house dust is a surprise to most people, since the pesticide was banned in the U.S. in 1972. But a house is a little like a living organism: once it absorbs a contaminant, it may never purge it completely. Dust in our homes, says Beamer, especially deep dust in our carpets and furniture, is a conglomerate of substances over the life of the home and can provide a historical record of chemicals that have entered it. contaminant n. 污染物;致污物 purge v. 净化;清除 The mess that originates within the home is a lot easier to measure and control. The more people who live there, the more skin thats going to be shed, the more pets, the more animal fur. And, as Mom always warned, the more you walk around the house while eating, the more food debris youll drop on the floor which also attracts more insects that will die, decompose and add their own special zest to your dust. Cooking smoke and tobacco smoke, which are the most obvious contributors when theyre being produced, actually make only a small contribution to what winds up on floors and surfaces. The tiny size of the particles makes them likelier to rise and adhere to other surfaces or simply remain in the air than to settle. shed v. 散发;流出 wind up 卷起;扬起 It goes without saying that your home will never be dust-free, but there are ways to reduce your own dust loading and its important that you try. Dust mites, which feed on shed skin, produce allergens that are known triggers for people suffering from asthma. Same goes for cockroach dust, especially in cities. No one needs much convincing about the wisdom of getting rid of arsenic, and the good news is that about 80% of it can be removed simply by cleaning floor dust regularly. | 
