Contribution of Tire Weights to Lead in Runoff
Research Idea Scope
Lead tire weights used to balance wheels may be a substantial source of lead in the highway environment. These weights are sometimes released from wheels and then abraded by traffic,releasing lead into the environment. Lead wheel weights are used worldwide to balance vehicle tires. An estimated 64 million kg/year (70,000 tons/year) of lead is used worldwide in the manufacture of wheel weights. Automobile and light truck wheel weights vary in size and weight, ranging between 5-150 millimeters (0.2-6 inches) in length and 7-113 grams (0.25-4 ounces) in weight. A typical vehicle contains between 200 and 250 grams of lead in wheel weights. Excluding the vehicle’s lead-acid battery, wheel weights are the number-one ongoingautomotive use of lead.Material collected during street sweeping operations will be analyzed. An attempt will be made to extract both whole and abraded wheel weights from the other material collected using densityseparation. This would provide a good measure of the amount of lead lost from wheels on a curb mile basis. These lead weights could be placed in a water solution with a pH similar to that observed in rainfall to determine the rate of leaching. The weights could also be tumbled to simulate abrasion and then retested to determine if broken surfaces increase the rate of leaching.Product: Information on the amount of lead retained in the highway environment.
Urgency and Payoff
The U.S. EPA has declined to regulate the use of lead in wheel weights based on the limited data available (U.S. EPA, 2005). They indicated that additional information related to
environmental impacts in the highway environment was needed. The purpose of this research is to provide this information:
1) Whether abrasion of lead wheel balancing weights occurs on the road, and, if so, the extent of the abrasion and the mass of lead lost from the abrasion;
2) The contribution of lead from wheel balancing weights to the overall levels of lead near roadways;
3) The quantity of lead from lead wheel balancing weights deposited on highways that subsequently enters various environmental pathways; and
4) The percentage of deposited lead that enters each pathway (to determine which pathways are of concern).
The work will include collection and evaluation of the amount of lead contributed to highway runoff by lead tire weights. This evaluation includes the contribution of both in-place weights and weights lost during use.
Urgency – Metals are a target constituent for DOTs and must control them in their discharge, to the MEP. This research will assist DOTs in prioritizing the sources of lead in their runoff, and allow them to fashion effective mitigation programs (BMPs). This work is particularly urgent in that metals TMDLs are becoming common across the country and this research will be an important component for use in the TMDL implementation process as well as for the traditional elements of the DOT stormwater program.
AASHTO Stormwater Management Community of Practice - State of the Practice Report, May 2011