Steel dust quickly turns to iron oxide in the environment, which is a fairly common natural mineral (it’s the reason red clay is red). To be fair, there might still be some slight negative effects to ecosystems which do not naturally have a lot of iron oxide at the surface, but that wouldn’t even be a rounding error compared to the harmful environmental effects of tires and asphalt. Also, steel dust is very heavy so there’s essentially no chance of it getting into the air and inhaled.
Steel dust quickly turns to iron oxide in the environment, which is a fairly common natural mineral (it’s the reason red clay is red). To be fair, there might still be some slight negative effects to ecosystems which do not naturally have a lot of iron oxide at the surface, but that wouldn’t even be a rounding error compared to the harmful environmental effects of tires and asphalt. Also, steel dust is very heavy so there’s essentially no chance of it getting into the air and inhaled.