Dust. Who knew?

A few years ago, I wrote a novel called “Motes.” The title of the book comes from the term used to describe particles of dust. Each particle is called a “mote.” There are alien creatures in the story from ten light-years away who are smaller than a dust mote. A human boy in the story sees one of them that appears to be behaving in decidedly non-dust-like ways and traps it in a peanut butter jar. You might be amazed at the story that develops from that.

Well, that’s enough shameless self-promotion. Let’s get on with the discussion. Since I wrote a book about dust-like things, I did a bunch of research about dust. It’s pretty fascinating stuff, actually.

I love math. I love everything about numbers, so a lot of what I am going to talk about centers around the concept of examining dust and figuring out the percentages of its constituents. Hang on and get your nerd on.

The average house in the United States collects a whopping 40 pounds of dust in any given year. Forty pounds! Wow! Locate a five-year-old. If it’s a kid from your own family, pick the child up. The average weight of a human that age is about forty pounds. Be amazed at how much dust that represents. (If it’s a stranger’s kid, ask politely to hoist their offspring and then feel awkward when they grab the tyke’s hand and dart away, fumbling for their pepper spray.)

You’ve probably heard that a certain percentage of the dust you find lying around your house is actually dead skin cells. Yum. That’s actually true. Let’s figure out how much.

The average human being sheds about 1/3 of an ounce of dead skin every week. Going back to that average house with the forty pounds of dust in it, let’s figure out how much of that is skin. In the United States, the average population of any given household is 2.6 people. That seems small to me, but that’s the number published. Two-point-six people times 0.33 ounces of skin each week, times 52 weeks in a year, works out to just a little under four pounds of skin lying around the house after a year of skipping the dusting routine. Your average adult chihuahua weighs anywhere from about 3.3 to 6.6 pounds. Now, imagine a wad of skin flakes the size of an ankle-nipping chihuahua. That’s what collects in your house in a year. Of course, if there are more than the average 2.6 people living in your house, you’ve got even more skin in the game, so to speak.

People like to throw numbers like 70 or 80 percent around when they talk about how much of what you see as dust being human skin. I think they do that just to creep everyone out, but the 10 percent that is closer to the truth is gross enough.
What about the other 90 percent? What’s it made of? The answer is that it varies. That’s pretty unsatisfying, but a lot of factors contribute to your own personal dust pile. In general, stuff you’ll find in there includes:

  • Pollen
  • Hair
  • Fibers from your clothing and upholstery
  • Paper
  • Dirt from outside
  • Cosmic dust—yes, particulates from space actually can be found on your fireplace mantle
  • Other “stuff” that could be metals, insect parts, and things associated with dust mites

Dust mites are creepy all on their own. They eat dust, primarily the dust from organic sources in the list above, and they poop out material that can trigger allergies in humans. When people say they are allergic to dust mites, they are really saying they are allergic to dust mite feces. Dust mites are particularly fond of dead skin cells when it comes to their menu choices. That means you will find loads of them in places where humans sleep.

Your mattress right now is home to somewhere between 100,000 and 10,000,000 Dermatophagoides farinae (the scientific name for dust mites found in North America). That’s a wide range, but it varies depending on how often and how vigorously you launder your bed coverings, not to mention how many people share your sleeping place. There are so many of these little varmints in your bed that as much as ten percent of the weight of a two-year-old pillow may be made up of dust mites and their droppings. Sweet dreams, by the way.

Don’t worry. If you are not allergic to their droppings, the mites are harmless. They only eat dead stuff. Now, don’t you feel better?

The thing on the list that really grabs my attention is “cosmic dust.” In my book, some of that dust is actually living creatures from a distant planet, along with their vehicles and other technology.

While writing that story, I became keenly aware of dust on surfaces and floating in the air around me. (By the way, a speck of dust can float in the air in for up to five days before settling down.) I wondered many times then, and since, just which particles I see around me are from extraterrestrial sources. As it turns out, some 40,000 tons of dust land on our planet from space every year. Most of that is from micrometeorites that fall through the atmosphere undetected. Notice I said, “most.”

I can’t help but wonder what else might be in that 40,000 tons. That’s a bunch. The blue whale is the largest animal ever known to exist. They top out at about 130,000 pounds. It would take over 240 of the biggest ones to total 40,000 tons. Do you think at least a few of those little motes of dust might be something more interesting than particles of meteorites?

Hmmm…

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