These impurities are byproducts of the manufacturing process. Little is known of its level of toxicity. It is probably safe to ingest, but does not have any ergogenic effect. Some unscrupulous companies will cut their creatine with Maltodextrine. So a 500 gram bottle may only contain 250 grams of creatine.
Lets look at the following chart.
So, as you can see, German creatine has less impurities than any other. The companies we carry here at Frontier Nutrition are only of the highest quality German Creatine. If you are trying to build quality muscle, make sure you add a whey protein powder.