Four small pieces of lead may not seem like a big deal. Each wheel on your car likely has a little bar of lead on its rim, in the form of a wheel weight. But picture the magnitude of vehicles on U.S. roads and you see quickly how all that lead adds up to a significant problem.
For decades, wheel weights have largely consisted of chunks of lead clamped to the wheel rim. Why lead? Because it is cheap and heavy, allowing the use of relatively small weights to balance wheels. However, the toxic metal can cause brain damage and other nervous-system disorders in people.