Regular washing out will not only make the pole last much longer, but will also reduce the black residue from these poles. The reason that the poles give out black dust in use is due to the fact that they pure carbon fibre poles. Fibre Glass pole will not produce black dust in use, unless they have been made with black resin - which we do not think many are. All poles with a carbon content will, at some point, produce carbon dust as they wear. This residue is produced when small grit/sand particles abrade the inner/outer surface of the poles as they telescope.
The easiest way of controlling this is to wear gloves whilst working. We have worked with carbon fibre poles now for about 9 years and have always worked with some kind of hand protection as a matter of course; the benefit of this is that we never get 'black' hands. Wearing gloves of some sort should actually form part of a good method and H&S statement for any contractor as it also protects against contaminants that the hose picks up. When the weather is not cold we recommend wearing a pair of disposable Nitrile gloves (£6-7 per 100 on eBay), it also means that you can peel them off and eat lunch or conduct business with clients with completely clean and hygienic hands.