In a Little Britain sketch the woman who runs dieting club Fat Fighters quizzes here charges with "How many calories in dust are there? Anyone?" before answering herself, "That's right, there are no calories in dust!"
Maybe there are no calories in dust, but according to one big business, there's definitely money in it.
In probably the most high tech solution to proving that there is, in fact, brass in muck, waste management firm Veolia has developed a plan to sweep up tens thousands of tonnes of road dust and extract the precious metals that form part of it. Metals like platinum, palladium and rhodium.
These aren't just lying around, they've come from various sources, including catalytic converters in cars, mobile phones, computers, dental fillings and white gold.
Twigs, fag ends
Once gathered, the dust is taken up to their plant in Rugby where the stones, twigs, fag ends, aluminum cans and bits of plastic are separated from the rest then a big magnet used to pick up steel and iron. In a year, they reckon they'll be sifting through around 30,000 tonnes of street sweepings.
Though it sounds very technical, it's a technique that brings together soil washing, which isn't new, and Veolia's own method of extracting the palladium from the residual dust from that washing.
With a better understanding of the price of precious metals, it all becomes a bit clearer why there are so many recycling companies out there ready to snap up our old mobile phones or computers. Though they may not work anymore or have the latest bells and whistles, they do still have value in the precious metals market.
And our street sweepers? Next time I see one, it won't be some solitary soul cleaning the pavement with his barely-bristled brush and filthy cart. No. He's like the gold miner of yesteryear heading to California to strike it rich through sheer hard graft come rain, wind, hail or snow.
Though instead of reaping the direct fruits of his labour, he's on minimum wage.