Astrophysicist Karel Schrijver, co-author of Living With the Stars: How the Human Body Is Connected to the Life Cycles of the Planets, and the Star, talked to National Geographic about how this dust affects humans. "There's still an awful lot of dust floating around," she says. "...That dust falls onto the Earth all the time and has from the very beginning. It's why the planet was made in the first place. Nowadays, you don't even notice it. But eventually all that stuff, which contains oxygen and carbon, iron, nickel, and all the other elements, finds its way into our bodies."
Space is one of three sources of dust on Earth. The other two main sources are your home (dead skin cells, pollen, dust mites, and more), and dry, arid places like deserts. In fact, the dust from the Sahara Desert can blow all the way over to the Caribbean.