Well they won't be certified virus free unless they were seed potatoes. When I was a kid they grew seed spuds around where I lived, and a farmer told me you could use chemicals on them that you can't use on food crops. This is why you get better quality spuds for seed, and mustn't eat them... lots of effort goes to making them this way.
You might get away with it if you use normal spuds, but unless you're completely skint you should use seed ones...