[00:02] of household dust comes from dead skin and hair. It's mostly a mix of soil, outside, along with tiny textile fibers from inside your home. But, that's not all. 1 g can hold thousands of mites, microscopic spider relatives that feed
[00:17] thousands of their fecal pellets. When inhaled, their proteins can weaken your airways' protective barrier, causing one of the most common allergic reactions on the planet. The smallest particles are even worse. Below 2 and 1/2 micrometers,
[00:31] your lungs and cross into your bloodstream, contributing to millions of make rain. >> [music] particle, giving water vapor something to condense on. That's how 28 million
[00:46] tons of Saharan dust replaces the phosphorus tropical rains wash from the Amazon soil every year. Without it, the rainforest would slowly starve. And Every year, Earth gets showered with
[01:00] over 5,000 tons of comet and asteroid dust. So, the next time you dust, remember, for every pinch of regular household dust, there's a few nanograms household dust, there's a few nanograms of stardust.