污染对公众健康构成严重威胁。

Pollution poses a serious ___threat to public health.

气候变化是一个需要立即采取行动的全球性威胁。

Climate change is a global ___threat that requires immediate action.

这种新病毒被认为是对民众的一个重大威胁。

The new virus was considered a major ___threat to the population.