Hmmm
If you're in the US, then as Xanthippe says above - the US had their first clean air act introduced then: The Air Pollution Control Act of 1955
BUT, of course, the very reason it was introduced was because of low air quality before 1955 (!!) - ie the 1948 Donora Smog
Could it though be a mash-up of the following??....
Awake 22 April 1971, page 20 - Can Man Solve the Problem?
A few streams, a lake here and there, the air over a few cities—that is the extent of success man has had in trying to reverse the disastrous trend. What of the overall situation?
Facing the overall situation realistically, there is little ground for optimism. For example, look what happened in New York city. Back in 1955 its air pollution commissioner predicted: “In 10 years, our city will be a good place to inhale in.” A researcher also predicted: “By 1965 the air breathed by a man crossing 42nd St. will be as fresh as the air in a Swiss mountain pass.”
Persons living in New York city today would call those predictions ridiculous. New York air is so heavily polluted now that much of the time it is rated either ‘unsatisfactory’ or ‘unhealthy.’ Those optimistic predictions were not based on reality.
I understand that the above Awake! was a 'special' with articles in the whole issue devoted to the front page theme: "Earth's Future - Garbage Dump or Garden Home?"
BUT the only public talk outline reference to the magazine issue is in the introduction of Public Talk 14 - and it isn't really related
14: A CLEAN PEOPLE HONORS JEHOVAH
PHYSICAL CLEANNESS IS ASSOCIATED WITH SPIRITUAL ACCEPTABLENESS
Jehovah is a holy God (it-1 1127 para 17)
He is profaned by uncleanness, physical or spiritual (Isa 1:16)
Israelites had to wash themselves and their clothing for awesome assembly at Mount Sinai (Ex 19:10, 11)
Aaron and his sons had to wash with water from large copper basin before serving in the tent of meeting (Ex 29:4; 30:18, 19)
Cleanness in the Israelite camp was required by the holy God (De 23:10-14; g81 5/8 14; g71 4/22 28)