As tires wear out, rubber is presumably deposited on the road surface. Where is all that rubber? –R.D. Morgan, Camden, South Carolina
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Tires are a mix of materials, mostly synthetic and natural rubbers but also including carbon black, oil, sulfur, steel, and chemicals added as antioxidants, strengtheners, and fillers. They also contain varying amounts of potentially hazardous metals such as zinc, nickel, chromium, cadmium, and copper. As you drive, and especially as you corner and brake, your tires continually abrade against the road surface, and to some extent wear away just due to flexing as they roll along. This tire wear takes the form of rubber left on the road, heavy particles that quickly settle on the road and shoulder, and lighter particles that become airborne.
Those who aren’t latex-sensitive don’t get a break. Fine rubber particles, whether latex or synthetic, can lodge in your lungs and even enter your bloodstream. The Environmental Protection Agency has a whole category designated for such problematic particles: PM2.5, or particulate matter less than 2.5 microns in size. Excessive exposure can lead to reduced lung capacity, bronchitis, asthma, accelerated heart disease, and death. One study claims that nearly 60 percent of airborne tire particles are small enough to be easily inhaled. I’ve heard tell that radial tires produce a finer dust that’s more hazardous than what’s produced by older-style bias-ply tires; while that’s plausible given tire construction differences, it’s difficult to know for sure.
Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.
