If you were really worried about impurities in your food then you wouldn't be eating food. There's impurities in everything, even the most wholesome sounding organic stuff. The whole "there's blood and pus in milk" is a fact yes, but it's also a scare tactic used by the PETA crowd. Guess what, there's cow's blood in your steak too! OMG NOOOOooo
Anyway, cow's milk is fine unless you're lactose intolerant. Like me. Then it's pretty much a hateful poison that makes your guts explode.
Oh and I prefer vanilla Silk to Rice Dream.