Surely the stories of dark air over London had something to them. And they did. Air quality in London steadily deteriorated until the beginning of the 20th century. But just as the air dirtied (with no one’s intention by the way) so too did it clean. Here is a a chart via Matt Ridley (I cannot find the original that I scanned it from right now on the road):
Sulfur dioxide is the top line. Smoke is the bottom line. Go see when the British equivalent of the EPA was founded if you are in the mood for a fun search. Aside: in terms of water quality, the Thames had NO fish for over a century since the Great Stink, by 1968 had over 40 species of fish living in it (I probably still would not have eaten them!).
I looked carefully to find a Policy Review edition in my library entitled, “For Peat’s Sake,” an article about the fishery in the Adirondacs around the days of Teddy Rooseveldt.
Going to post this to see if it goes through….
In any event, it turns out there were fires in the Adirondacks around then, which produced ash, which is alkaline like lime, the result of which was to make all of the water upstream of the Hudson hospitable to trout, just as limestone creeks are everywhere.
For one reason or another, the burned trees were replaced by other pine trees. This all happened during a time when the EPA and the Sierra Club were not in charge.
The result was that the pine needles, in combination with shade and decomposition, returned the lakes in the Adirondacks to the state they were before the fire — acidic, clear lakes. No trout, but smallmouth bass. The captains of industry would flock to Saranac Lake to watch their families water ski on the clear water.
Want trout in the lake? Dump in a few tons of lime, or toss a match and start a fire.