Well, this is an interesting question in one way, because it shows that there must be some word going around in parts of the world, or wherever, that wasabi--which is somewhat similar to horseraddish--is or can be dangerous.
I think, Pavel123 san, that it would be good to also explain how it is you have come to think that wasabi could be dangerous. As far as I know, it is not. I love to use just a little bit more with my sushi than what the sushi chef normal applies under the slice of sea creature--it's a rush !!
I'm not so certain that there is, in the final product, actually, so much that can be compared between 'karashi' and 'wasabi.' They are rather two different tastes, and effects--to a connoiseur--(we could well say) are different enough, not to mention the looks.
I also understand that there would be many who do not really know about such things in detail, and may not have had the actual experience of seeing or taste-testing them, so I will give that degree of not knowning, a place in the random, common universal events catagory.