Speck by speck,dust piles up

Although she was working with inchoate historical data,Mahowald said,“Nobody has come up to me and said,‘I don’t believe you.’ ” Climate change seems to be one source for all the new dust. Human land use is another.

Alternately,I asked,have researchers considered the possibility that the dust might have come from under my bed? Recently,my wool Schlitz hat fell down there. When I retrieved it,the hat had grown a full,gray rabbinical beard. “That doesn’t have anything to do with it,” Mahowald said,without pausing to consider my hypothesis. Her study didn’t measure dust from human sources,like our burping tailpipes and pilling sweaters,she explained. “Dust is such a vague term. I’m being very particular here: soil particles suspended in the atmosphere.”

If the future is looking like a dustier place,we could start by closing the windows,said Jane Novick,who lives on the fourth floor of a prewar building on Fifth Avenue,overlooking Central Park,New York. The buses and taxis crawl by all the time,she said. “I clean constantly,but not crazily,” Novick said.

All that cleaning can have an unintended consequence: Oddly enough,it actually breeds dust. In fact,cleaning is one of the three main sources of household dust,according to research on indoor particles. Cooking is the second; movement is the third.

Every step disturbs tiny particles of dirt,fibre,soot,pollen,paint,food and dead skin. In common parlance,it’s all dust,said Richard Flagan,the chairman of the chemical engineering department at the California Institute of Technology. As soon as these motes lift off a carpet (or a TV remote),“you induce air currents” that propel them around the room,he said.

Several thousand particles of this stuff will waft in any cubic centimetre of air,a space the size of a sugar cube. We travel through life emitting what scientists call “a personal cloud” of dust.

A piece of dust that is 100 microns in diametre (the size of a dot of chalk powder) will fall about a foot a second,said Flagan. A mote that is 1 micron in diametre,the size of a bacteria,will fall just 30 microns a second. And many of the particles created by cooking,which is a leading source of indoor dust,measure less than half a micron across.

Where does dust this small go? Anywhere it wants. Trying to herd it into a dustpan is either an act of hubris or a clown routine. Given these absurdities of scale,cleaning will inevitably scatter dust around the room. Still,the forces of chemistry and physics can help.

There may be no more primitive dusting tool than a damp cloth. You will not see it advertised on late-night TV. But that doesn’t mean it won’t work. “The reason that you use a wet cloth rather than a dry cloth,” Flagan said,“is the liquid introduces capillary forces.” The dust will bond to the wet surface,he said. “And then the particle doesn’. Maybe the dust stays,maybe not.MICHAEL TORTORELLO