Used after a noun to mean 'when it comes to...' or 'as for...', introducing a specific topic or area of concern.
子供となると、風邪をうつしやすいから注意が必要だ。
When it comes to children, they catch colds easily, so you need to be careful.
仕事となると、彼はとても真面目になる。
When it comes to work, he becomes very serious.
お金となると、人は判断を誤りやすい。
When money is involved, people tend to make poor judgments.
A conjunction meaning 'if that's the case...' or 'if it turns out that...', used to introduce the consequences or judgments in that case.
彼が本当に来ないとなると、計画を変えざるを得ない。
If it turns out he really isn't coming, we'll have to change the plan.
それが事実となると、大きな影響が出るだろう。
If that proves to be true, it will have a big impact.
予算が足りないとなると、計画を縮小するしかない。
If the budget is insufficient, we'll have no choice but to scale back the plan.