Car owners and fans of NPR's Car Talk  know that when you get new tires or rotate them, the tires need to be balanced . Often, those tires are balanced with lead weights , which either disintegrate over time from daily driving, releasing lead powder into our environment, or are knocked off by curbs and unkempt roads. Maine , Vermont , and Washington  have banned lead weights, and at least California  and Iowa  are considering similar action. The Environmental Protection Agency  has taken notice, recently signaling that it will work to institute a nationwide ban of leads weights as Europe has already done.
It is well known that exposure to lead  causes a variety of health maladies, such as brain and nervous system disorders, high blood pressure, and reproductive and development problems. However, the EPA estimates that 2,000 tons  of these small lead weights are lost from vehicles and released into our environment each year, the weight equivalent of 1,364 Toyota Prius  hybrids.
The Sierra Club , Ecology Center  and other environmental groups have long petitioned  for the ban, and were rebuffed by the Bush Administration in 2005. Yet, the EPA is now changing course . Adding to the pressure on the EPA to ban the lead weights has been the action of states in recent years. A senior EPA official cited the increase of state bans  as one of the pressure points leading them to act, saying "a number of states have moved to ban these weights, so there's clearly rising concern."
Ecology Center - www.LeadFreeWheels.org 
Sierra Club and Ecology Center - EPA Moves to Ban Sale of Toxic Lead Tire Balancing Weights for Cars