For pollution, at least CO2, 300M lb is 136k metric tons. I didn't know the water to CO2 ratio for solid rocket motors, but I'd guess maybe half is CO2. Cars produce 1.5B tons of CO2 per year in the US, so the CO2 would be about equivalent to about 24 min of driving cars. That doesn't seem too unreasonable.
But maybe you were taking about the metals? I don't know how much of an issue those are.
Unfortunately this isn't complete combustion. There's a shit ton of PM and everything else. Ever go to a big show? They have to take pauses for the smoke to clear so that you can see the next batch.
Everything is unnecessary. We could just off ourselves and there’d be no more pollution. The only reason our existence matter is the way we feel about it. Which is the same reason fireworks matter.
That depends on a lot more factors for how dilute it gets. I didn't know how likely it is for the air currents to dilute the aluminum exhaust over a large enough area before it rains. Maybe someone could do some analysis, but I don't know how.
It's not worse, it's different. CO2 kills everything on earth but that takes a lot of it. The toxins you listed can give a community long term health issues without that much exposure. It's a local problem vs a global problem.
Sorry, completely off-topic, but your name keeps reminding me of rock-a-doodle. I know his name is completely different, but it has the same flow and a really similar sound. Chanticleer. Prounounced Chant Eclair, a french pun for "sing loud and clear".
Personally I think it's important to understand Co2 emissions aren't the only factors in the pollution of air quality. Like you mentioned, heavy metals are a big factor in climate (for example how private jets still use leaded fuel).