Which pollutant is not usually produced or added to the environment by human activities?

Question

(1).sound
(2).pollen
(3).radiation
(4).smoke

Answer 1

The answer is that human conduct affects all of the above.
Probably the developer of the question is looking for (2).pollen

The amount and kind of pollen is definitely impacted by human activity. In the southwest part of the USA, where there is naturally a very dry climate, irrigation has allowed us to introduce many plants that did not exist there a century ago. The pollen count is therefore significantly different than it used to be. People used to move there to avoid contact with many pollens that are now common in that area.