Dunno about how the US does it, but in Germany, urban areas have the road wastewater go into the sewers so it passes treatment plants. In rural areas tire dust

Dunno about how the US does it, but in Germany, urban areas have the road wastewater go into the sewers so it passes treatment plants. In rural areas tire dust isn't as much of a problem because cars there keep their speed - it's acceleration and deceleration that produce tire dust.