These are two pictures taken down my hand-held fibre microscope - you can see the core and buffer of two examples of fibres that were spliced maybe three months ago in a new building. I suspect builder/decorator dust contamination and even though they have had their cover-pieces on they aren't air-tight and so we're now looking at an extra 0.2dBs of loss on those circuits.
Not a whole hill of beans, but worth noting. It is jolly hard to position and focus an iPhone over the eyepiece, but here is an image of what a new, uncontaminated fibre pigtail looks like (these are all multi-mod OM3 BTW). Aside from the JDSU microscope I also carry a Cletop cleaner when I'm on fibre mission. It's a small cleaner with a replaceable cartridge that allows you to swipe the end of the patch cord or pigtail with a fresh piece of dry-clean, lint-free material and it removes even stubborn stains.