The myth

The chief ingredient of household dust is human skin; 70, 80 or 99 per cent, in various versions

The "truth"

There seems to be no basis at all for this Well Known Fact – except wishful guesstimating on the part of those advertising copywriters whose job it is to sell us anti-dust devices. There’s no evidence to suggest that dust is mostly made up of any one ingredient; rather, it is a delightful salmagundi or potpourri of everything that is likely to be drifting around your house – cat dander, face powder, cigar ash – or that might be blown in every time you open the door, including soil, pollen, insect excreta, and general industrial pollution. The precise ingredients and proportions present will presumably depend in part on where you live, as well as how – Bognor dust is likely to be sandier than Hackney dust – and on the time of year. Human skin will certainly be on the list, but it is shed chiefly when washing, and therefore disappears down the plughole, not into the dustpan.