My Lungs Wish We'd Do Something...With so much attention paid to vehicle exhaust emissions, we sometimes forget that the engine isn't the only thing creating air pollution on an automobile. As they wear out, brake pads, tires and other car parts, as well as the road sufrace itself, release particles of dust in the ambient air, and those cause cardio-respiratory problems to those who are exposed (and if those types of particulate matter are anything like diesel PM, they might cause lung cancer too). According to a study in the ACS journal Environmental Science & Technology: "these non-exhaust emissions make up a similar proportion of the airborne particulate matter (PM) resulting from vehicle use as exhaust emissions."
Green Car Congress reports:
Although the aerodynamic diameters of these non-exhaust particulate emissions tend to be larger than those of exhaust emissions, they still can enter the respiratory system and possibly lead to adverse health impacts. Sources and types of non-exhaust atmospheric particulate matter include:
Iron, copper, antimony, and barium from brake operation.
Road surfaces are generally composed of either concrete or aggregate with a bituminous binder and abrasion of such a surface is likely to result in particulate matter of mineral origin.
Tire wear is likely to result in predominantly carbonaceous particles, although small quantities of metals, in particular zinc which is used as a vulcanization activator, may be present.
Material resuspended from the road surface may include all types of vehicle abrasion debris, in addition to material from non-road sources which has been deposited on the road surface. This may include mineral dust from the local environment, typically including silicon, aluminum, calcium, and iron—particularly in arid locations. Within the United Kingdom, winter maintenance procedures involve spreading deicing salt on roadways, but the practices that are common in some northern countries of sanding roadways and fitting studded tires are not adopted.
We need to start paying more attention to this source of air pollution, especially because it won't be solved by a switch to plug-in hybrids or electric vehicles. Brake pad dust might be much lower because these mostly brake with regenerative braking, which doesn't use brake pads most of the time, but tire and road dust will remain a problem.
It might be hard to entirely solve this problem, but I'm sure that with some R&D and maybe some regulation to spur things along (because there are not really any market forces pushing in this direction), we could figure out how to have road surfaces and tires that produce less harmful particulate matter.