highest poisons

[KLPNO]

Hello everyone
I'd like to ask about the meaning of the phrase "highest poisons" in the following sentence.

But the air was breathable again, the wind having blown away the highest poisons.

Does "highest poisons" mean the most dangerous poisons?

[meez]

Depends on the context. Could be the most dangerous poisons or the ones which are physically highest in the air.

[KLPNO]

Depends on the context. Could be the most dangerous poisons or the ones which are physically highest in the air.

Here is what the author says about these poisons earlier:

Presumably the doomed were even more impressed, watching the tower of saltwater and foam soar high overhead, dislodged chunks of wood falling around them, and an endless thunder shaking the world as huge quantities of gas -- methane laced with hydrogen sulfide -- bubbled free.

[Anglika]

Even the context is not very helpful! I think the author is meaning the most dangerous poisons.