How road wear reaches the ground
Tires shed small bits of material as they grip and brake on pavement. The resulting particles mingle with road dust; wind and rain can carry them off streets and onto nearby ground. Synthetic fibers from clothing and other sources can settle there too. Once on soil, these particles are small enough to become part of the material earthworms encounter while feeding.
A living route below the surface
Earthworms do not sort food with precision. They take in soil containing decaying organic matter, digest what they can use, and pass the rest through their guts. The processed soil emerges as casts—worm droppings deposited on or within the ground. As worms burrow and feed at different depths, they can move particle-bearing soil downward as well as sideways.
That movement matters because it gives contaminants a route into soil layers that rainwater alone might not reach as quickly. How much material moves, and how deep it goes, depends on factors such as the particles’ size and the activity of worms in that soil. The worms are not destroying the rubber simply by eating it; some particles can pass through and remain in the soil.
Near roots is not the same as inside a crop
Moving particles into the root zone—the soil where many crop roots grow—puts them in closer contact with plants and soil organisms. But being near roots does not by itself show that a particle enters a plant or affects a harvest. It does mean that tire wear is not only a roadside or waterway issue: once deposited on land, it can be redistributed by the animals that continually mix the soil.
A worm’s cast can therefore act as a small delivery point, carrying road-derived material from the surface into the living soil below.
