He also expressed concern about Americans and other Westerners traveling to Pakistan and Somalia for terrorist training.

VOA: special.2009.10.17

Or in situations where you have concern for your safety or for other's safety.

或者当你在为自己或他人的安危感到担忧时，都可以使用这个句型。

I'm worried 课堂 - SpeakingMax英语口语达人