1. In what year did people begin to understand air pollution would be a problem? Explain.

1937 because UT's the answer of the historian questions

Explanation:

because thats yyh and because of it being like thaf

Before the Industrial Revolution, our planet's atmosphere was still untainted by human-made pollutants. At least, that's what scientists thought until recently, when bubbles trapped in Greenland's ice revealed that we began emitting greenhouse gases at least 2,000 years ago.