Yeah, but brakes are not not made from pure iron and you won't have atomic erosion. Silly argument, really. Notoriously, you could still find brake pads with asbestos not too long ago. Pretty much any fine dust is very unhealthy to inhale, but brakes and tires are made from material mixes you really don't want to breath in. Even the "inert" fraction we find as microplastics in everything, the rain, fish and newborn, and we're only beginning to understand their biological reactivity and long term health consequences.