Science Questions

Where does dust come from?

Sun, 9th Mar 2008

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Question

Nicholas asked:

I want to talk about dust. At this time of year the sun starts coming through the window and you can see the surfaces you've dusted carefully are covered with dust . You can actually see dust in the sun beams. I wanted to know where all this dust comes from. My dictionary defines dust as finely powdered earth, dirt etcetera, lying on surfaces and blown about by the wind. That strikes me as being all very well for agricultural dust but household dust is very different. I can't believe it's all my epidermal cells.

Answer

Chris:  I'm afraid actually, it is Nicholas, it's you and all the other people who have lived and visited your house.  The stats really stack up and they are really quite scary.  The average human loses about 30 or 40 dead skin cells every single second.  If you were to add them all up and put them in a giant bag over the course of a lifetime that would weigh about 1-and-a-half stone in dead skin alone.  Most of that debris you see lying around your house is dead bits of you floating around.  You're breathing that in, you're breathing in bits of your partner, your family, your visitors, your friends.  It's just bits of yourself.

Nicholas:  Well, I'll just have to accept that but even so 1.5 stone over the period of a lifetime doesn't seem like that much.

Chris:  Yes, but a skin cell is very, very tiny.  The weight of a cell is measured with about 9 zeros in front of it (10-9kgs).  It's tiny!

Nicholas:  But a particle of dust is not one skin cell, is it?

Chris:  No, these things are clusters.  They get stuck together and other fats and materials that are present stick them together.  As a result you end up with something that forms a blob of dust.

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