Hello.

I will really appreciate your help.
1) Is it possible to use "unknown" in the following context: "It is still unknown what effect the accident will have on the world."?
2)Is it possible to use "include" in the sentence: "The organization includes 62 nations."?
Thank you very much for your help.

Both are OK, but for some reason "not known" sounds better to me than "unknown" in the first sentence.

"Is comprised of" is better than "includes" in the second sentence. Otherwise, the organization might also contain anything.. like fish and bicycles.