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The Dirt On Dust

By Joe Palca

Published November 16, 2009 12:01 AM

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When you get right down to it, dust is pretty complicated. It also may be affecting your health.

Paloma Beamer of the University of Arizona spends a lot of her time thinking about dust — what it's made of and where it comes from.

Where Does Dust Come From?

Beamer says there are really only two places dust can come from: outdoors and indoors.

We are an important part of the process of getting the outdoor stuff indoors. We bring it with us when we enter a house — through "soil particles that come in on your shoes," says Beamer, or tiny particles suspended in the air when we open the door and walk in.

Then there's the indoor component of dust. "Like pieces of your carpet fiber or your furniture, your bedding, or anything like that that starts decaying," she says.

Then there are organic contributors. "Skin flakes and the dander off your pets, and other insects or bugs that might be in the home."

Now, as anyone who's looked under a sofa knows, there's dense dust and there's fluffy dust.

"A lot of the fluffy things, I think, tend to do more when you get a lot of fibers. In my house, it comes from cat hair," Beamer says.

Beamer's interest in dust stems comes from her effort to measure people's exposure to toxic substances. In a recent paper in the journal Environmental Science and Technology, she calculates the proportion of dust that's from indoor sources, compared with the amount from outdoor sources. She figures that one-third comes from indoor inorganic sources like carpet fibers. "Two-thirds comes from both soil tracked in, and the outdoor air particles," Beamer says.

She says it's important to know these ratios, because it will give a measure of the potential exposure people have in their houses when they live near a toxic waste site.

How the toxins in dust get into your body depends on the size of the dust particle.

Dustology

Andrea Ferro of Clarkson University in Potsdam, N.Y., is also a dust expert. She says some of the particles are small enough that they can float in the air, and we can get them into our lungs. Others are larger and tend to sink to the ground. Some are simple, made of only a single organic or inorganic compound. Others are complex.

"So you could have a particle that has an inorganic center and then an organic coating. So it can be very complicated," Ferro says.

One thing that's remarkable about dust is that it sticks around. Without vacuuming, Ferro says, it can stick around for a long time.

"We're finding things like [the pesticide] DDT in many floor dust samples," says Ferro. "We banned that decades ago, but it's still there."

In addition to breathing in dust though your nose, you can also ingest it by mouth. Heather Stapleton of Duke University studies the environmental chemicals that wind up in dust. You may not be in the habit of licking the floors or carpets in your home, but some younger members of your household might be doing essentially that.

"As a parent of a 6-month-old, I can't tell you how many times I look at my son, and I see him with his hands in his mouth all the time, or picking up a toy and putting it in his mouth," says Stapleton. "It's really difficult to quantify what mass of dust you're actually exposed to and any contaminates associated with that dust. But it definitely occurs."

Stapleton says she is trying to quantify this route of exposure. Her work focuses on a flame retardant that was banned from children's pajamas because of its potential toxicity. But it's still used in furniture and foam cushions, and somehow it's leaching out of those items and finding its way into the dust of a house.

Stapleton says there's a lot of work to be done in the world of dustology.

"Our understanding of how much dust a person is exposed to is very limited."

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View Transcript

STEVE INSKEEP, host:

Next, we're going to give you the dirt on dust. Even the most well-scrubbed homes will have some dust buildup somewhere, and the reason to remove dust is not just aesthetic. As NPR's Joe Palca reports, dust has some potentially harmful stuff in it.

JOE PALCA: As they used to say in Elizabethan times: How dost thou?

(Soundbite of vacuum cleaner)

PALCA: I tend to favor a vacuum. On the other hand, nature abhors a vacuum. But before we get into removing dust, let's talk a bit about what dust is and how it gets into your house.

Dr. PALOMA BEAMER (University of Arizona): Outdoor soil particles that come in on your shoes.

PALCA: Paloma Beamer is on the faculty of the University of Arizona in Tucson and something of a dustologist. Outdoor soil is one element in dust. Another is the tiny particles in air that float in when you open a window or door. And then there's the indoor component of dust.

Dr. BEAMER: Like pieces of your carpet fiber or your furniture, your bedding or anything like that that starts decaying.

PALCA: The indoor components also include certain bits of organic matter.

Dr. BEAMER: A lot of our skin flakes and dander off your pets and other insects or bugs that might be in the home.

PALCA: Now, as anyone who's looked under a sofa knows, there's dense dust and there's fluffy dust.

Dr. BEAMER: So a lot of the fluffy things, I think, tend to do more when you get a lot of fibers. In my house, it comes from cat hair.

PALCA: Beamer is interested in dust because it's one way people can be exposed to toxic substances. For example, for someone living near a toxic waste site, some of those chemicals can end up in house dust. The question is how much. In a recent paper in the journal Environmental Science and Technology, she calculates the proportion of dust that's from indoor sources compared to outdoor.

Dr. BEAMER: The indoor percentage would be around 34 percent, and then the two-thirds from outdoor comes both from soil tracked in and the outdoor air particles.

PALCA: But to understand the potential for exposure, it's also crucial to understand how dust can get into your body. Turns out, for dust, size matters.

Dr. ANDREA FERRO (Clarkson University): The big thing about particles and breathing particles is the size of those.

PALCA: Andrea Ferro is also a dust expert. She's at Clarkson University in Potsdam, New York. She says some of the particles are small enough that they can float in the air, and we can breathe them into our lungs. Others are larger and tend to sink more rapidly to the ground. One thing that's remarkable about dust is that it sticks around. Ferro says without vacuuming, it can stick around for a long time.

Dr. FERRO: And we're finding things like DDT in many indoor dust samples. We haven't had - you know, we banned that decades ago, but it's still there.

PALCA: In addition to breathing in dust though your nose, you can also swallow it. Duke University's Heather Stapleton is an environmental chemist. She says you may not be in the habit of licking the floors or carpets in your home, but some younger members of your household might be doing essentially that.

Dr. HEATHER STAPLETON (Environmental Chemist, Duke University): Being the parent of a six-month-old, I can't tell you how many times I look at my son and I see him with his hands in the mouth all the time, or picking up a toy and putting it in his mouth. So it's incredibly difficult to quantify what mass of dust you're actually exposed to and any contaminants associated with that dust. But it definitely occurs.

PALCA: Stapleton says it's really hard to estimate just how much exposure a person has to the chemicals in dust. But, obviously, reducing the amount of dust will reduce your exposure.

Dr. BEAMER: Keeping a well-dusted home, a well-vacuumed home will reduce the dust in your home the most.

PALCA: Paloma Beamer says you want to get a good vacuum, and if it has one, change the bag before it gets too full.

Dr. BEAMER: I think it's important to remind yourself to not just vacuum your floor, but also your upholstered furniture.

PALCA: Yeah. Oh, dear. OK. More work to do.

(Soundbite of laughter)

(Soundbite of vacuum)

PALCA: Joe Palca, NPR News, Washington.

(Soundbite of music)

INSKEEP: Dusting the globe. This is NPR News. Transcript provided by NPR, Copyright National Public Radio.

Source: NPR

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