That's a good question. I think if one were to wash thoroughly and allow one's hands to dry completely, that one would be better off than not washing at all, but I don't have anything to back up my guess. I suppose it might vary with type of contamination.

However, I don't normally encounter that situation. When I'm out back packing, I normally wash with treated water. There are also various types of hand sanitizers and baby wipes out there, although soap and water are considered to be the best, and soap and water don't develop antibacterial resistant bacteria.

One item of note: according to Discover magazine, one should scrub one's hand after soaping up for at least 30 seconds before rinsing off. Some friends of mine in the food prep industry say that washing twice at 30 seconds is what they've been taught.

Yes washing your hands is important when handling food for cooking but if the only water available is contaminated rinsing off with that water leaves your hands contaminated so the thing to do is to decontaminate the water. I have read about a doctor working in Africa that only had contaminated water so what he did was to use Potassium iodide in the saturated solution form, by adding ten to twenty drops to this water after about five minutes it was ready to drink.

Now this soulution of potassium iodide is also known as SSKI is probably can be obtained at a drug store, households today don't seem to keep this on hand as they did many years ago when it was known as tinture of iodine to use on scrapes and cuts.

So to sum up if you only have contaminated water to wash with if you had SSKI you could first treat it with SSKI before washing or for drinking.