But have you heard about thirdhand smoke?

知道“第手”吗？

Thirdhand smoke? I'm afraid not. What is it then?

“第手”？我恐怕不知道，那么，这个指的什么？

But now researchers are warning about what they call thirdhand smoke.

，如今，研究者对他们所称的第手发出了警告。