an unpleasant fog that smells bad

A miasma of pollution hung in the air above Mexico City. 污染形成的瘴气弥漫在墨西哥城的上空。

a very unpleasant general feeling or character of a situation or place

After he lost his job, he sank into a miasma of poverty and despair. 失业后，他渐渐陷入贫困与绝望之中。