[PRODIG] dust and hairs on a digital exposure?

[Pete Jenkins]

Hi Folks,  I have just done a shoot at a Travelling fair which has involved some reasonably long exposures (1/10th sec or longer)and small apertures (f22 and smaller) on a fairly wide angle lens (17-35mm).               I am quite concerned to see on some of these images what appear to be hairs and dirt.  Big black marks on the image.  They are very random and are clearly some sort of rubbish caught somewhere.  The lens ‘looks’ clean, so where would all this crap be collecting? What can I do.  Could it be the lens?  I only see it at very small apertures.   When I stop down and look through the eyepiece onto a light subject I can just start to see some of this muck, but nothing as bad as has appeared on these particular images.               What do I clean and how?  Oh yes it’s a Canon D10.                 Help                 Pete Jenkins