小編寄語：熟悉四六級閱讀理解題型的同學(xué)應(yīng)該都了解，英語四六級考試閱讀理解材料大多選自《時代》《衛(wèi)報》《科學(xué)美國人》等外刊。要想閱讀理解這部分拿到高分，必須在平常多閱讀，掌握新詞匯，鍛煉閱讀速度。但對于很多同學(xué)來說，如何每日在浩瀚的互聯(lián)網(wǎng)世界尋找合適的閱讀材料進行分析解讀是一項很耗時間的事情。為此，滬江英語每日精選《衛(wèi)報》《時代》等外刊上的文章供大家進行閱讀練習(xí)。

【今日閱讀推薦】本篇閱讀材料“灰塵背后的那些事兒”選自《時代》（原文標(biāo)題：What's in Household Dust? Don't Ask 2010.2 23）。如果大家覺得比較簡單，就當(dāng)作泛讀材料了解了解，認識幾個新單詞或新表達方式也不錯。如果大家覺得這些材料理解上有難度，不妨當(dāng)做挑戰(zhàn)自己的拔高訓(xùn)練，希望大家都有進步^^

It's hard to get too worked up about dust. Yes, it's a nuisance, but it's hardly one that causes us much anxiety — and our language itself suggests as much. We call those clumps of the stuff under the bed dust bunnies after all, not, say, dust vermin.

to get worked up 為某件事生氣；不開心

clumps of ?一團一團的

dust bunny ?積塵；灰兔子（關(guān)于灰塵的比較萌的說法）

But there's a higher ick factor to dust than you might think. And there's a science to how it gets around — a science that David Layton and Paloma Beamer, professors of environmental policy at the University of Arizona, are exploring.

get around ?傳播；散播

Layton and Beamer, whose latest study has been accepted for fall publication in the journal Environmental Science & Technology, knew a lot about their subject even before they set to work. Historically, everyone from chemists to homemakers has tried to figure out just what dust is made of, and the Arizona researchers drew their preliminary data mostly from two studies of household dust conducted in the Netherlands and the U.S. The American survey in particular was a big one, covering six Midwestern states. Layton and Beamer also included a localized study in Sacramento, Calif., that focused particularly on lead contamination. What all those surveys showed was decidedly unappetizing.

figure out ?理解；解決；計算

The specific dust mix in any household differs according to climate, age of the house and the number of people who live in it — not to mention the occupants' cooking, cleaning and smoking habits. But nearly everywhere, dust consists of some combination of shed bits of human skin, animal fur, decomposing insects, food debris, lint and organic fibers from clothes, bedding and other fabrics, tracked-in soil, soot, particulate matter from smoking and cooking, and, disturbingly, lead, arsenic and even DDT.

"There are more [components]," Beamer says. "Dust is a hodgepodge of all sorts of things. It would probably be impossible to make a list of all the possible items."

But dust's ingredient label is not the whole story, since all of those flecks and bits behave differently and present different levels of health risk. To investigate those factors more closely, Layton and Beamer developed a computer algorithm that looked at the size, source and toxicity of dust particles as well as how easily they enter the house, if they ever exit and, if so, by what route. That information, by extension, can provide at least a rough sense of the dust load in your own home.

As a general rule, the majority of household dust — about 60% — comes from outside, through windows, doors, vents and, significantly, on the soles of your shoes. Smaller dust particles — from 28 to 49 microns, or thousandths of a millimeter — tend to stay on your shoes. The rest is shaken off inside. A higher share of the dust that floats in the air gets deposited, but again, there's a lot that determines how much any one home will get.

"Here in Arizona," says Beamer, "where we leave our windows open most of the year and have an arid climate, we would probably have a higher ratio." Industrial centers or sooty cities have plenty of dust too, though for different reasons.

arid adj. 干旱的；不毛的

ratio ?n. 比例

There's not much to fret about in simple particles of dirt or organic materials such as pollen (though they can trigger allergies), but lead, arsenic and DDT can be a more serious matter. About one-third of the arsenic in the atmosphere comes from natural sources — volcanoes principally. The rest comes from mining, smelting, burning fossil fuels and other industrial processes. Even in relatively low concentrations, arsenic is not without risk, especially to small children who play on the floor and routinely transfer things from their hands to their mouths. The same is true for lead, which comes less from wall paint — the source most people would expect — than from auto exhaust, smelting and soil deposits. "Lead loading on floors is a key determinant of blood-lead levels in children," Layton and Beamer wrote in their paper.

fret about ?因……焦急；為……煩惱

particle n. 顆粒；微粒

pollen n. 花粉

low concentration ?低濃度

determinant adj. 決定性的 ?n. 決定因素

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. 凈化；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 that's 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 you'll 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 they're 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. 散發(fā)；流出

wind up ?卷起；揚起

It goes without saying that your home will never be dust-free, but there are ways to reduce your own dust loading — and it's 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.

it goes without saying ?不言而喻；不消說

allergen ?過敏原；反應(yīng)原

None of this means that dust poses a clear and present danger or that you need to take any extraordinary measures. Just clean regularly, don't smoke, eat at the table — and try not to freak out. Dust bunnies are still only bunnies; you may just want fewer of them.

freak out ?嚇壞了；崩潰

Question time:

1. How does dust come into our houses?

2. What's the key factor of blood-lead levels in children according to Layton and Beamer' papaer?

3. How to get rid of the dust in house?

【參考答案反白可見（按ctrl+A即可）】

1.?Generally, the majority of household dust — about 60% — comes from outside, through windows, doors, vents and on the soles ofour shoes.

2.?Lead loading on floors.

3.?It's important that you try, just clean regularly, don't smoke, eat at the table — and try not to freak out.

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