[@Unfortunately]Say that to the Dinosaurs.
Dust clouds high in the atmosphere can lead to environmrntal catastrophes including but not exclusive to mini iccice ages.
Also dust powder in your lungs is a very serious healh issue, just ask people who know about volcanic catastrophes.
Heavy metal particles are even worse and nah, they would contaminate the landscape for long and you won't be happy for it. Check reports on the Gulf War's efects.
BTW, people are alreafy living in Hiroshima and and Chernobyl. You confuse radioactive materials with viruses and neurotoxins. Thing is dangerous but its effects are more subtle than some super lethal zone which you can't approach without dying.

Lastly, point your hair drier and laser pen at yourself, just for a minute. If you caugut cancer I am so sorry and I pay your treatment. If not then that's exactly what you can expect with pure nukes. Sure, unlucky dudes caught in the close proximity of the detination may suffer fromadiation poisoning but that's like saying frag grenades are contaminating because a stray sharpnel can wound people. Pure fusion nukes aren't exactly Disney Land and there coule complications wr didn't considered before but from what we know they are sure as hell more eco friendly than meteor impacts and kinetif bombardment.

As for launching kinetic rods via railgun mechanism. It may help but it defeats the whole point on them being cheap. The system would still cheaper per shot than a nuke but you're getting dimnishing returns. That abd you can only get so far by accelerating a multi-ton projectile. Try how crazy amount it needs by just inputing the KE formula of E= 0.5m*v^2
That and even if it's fast it ravels in a straight line for entire hours. More tnough time to predict its course and shoot it down.

I don't wish to turn this game into a number crunching science fair. I am merely giving you the correct answers.