Pilot Study of the Relationship of Regional Road Traffic to Surface-Soil Lead Levels in Illinois

摘要

Leaded gasoline has been used as fuel for trucks and automobiles in the United States since 1924; it has been implicated as a source of lead that is deposited on the soil and eventually can be ingested by small children, contributing to their burden of this toxic metal. The lead content of 667 surface-soil samples (taken at depths of 0-5 cm) and 159 subsurface-soil samples (from depths of 25-30 cm) collected from Illinois play areas near roads was measured and related to traffic variables. The samples were collected between June and October of 1985, and their measured lead levels exceeded the average natural background level for Illinois soil. The highest lead concentrations were found in samples from the six-county metropolitan Chicago region, where both traffic volume and traffic density are higher than in the rest of the state. Regression analysis showed significant correlation of lead concentration in the top 5 cm of soil with three variables (traffic density, distance from the busiest nearby roadway, and traffic volume), in a log-log relationship. The lead levels in soil samples taken near high-volume roads in the six-county suburbs of Chicago were similar to those in samples taken near high-volume roads within Chicago. This pilot study shows that lead accumulates in soil away from painted structures and known industrial lead sources, in a pattern at least partially related to traffic activity on and distance from nearby roads. Further research is needed to (1) better define traffic density, to improve understanding of the mathematical correlation between traffic and soil lead levels; (2) evaluate soil characteristics that can affect lead concentration; and (3) develop a standard method for measuring the lead content of urban surface soils. 82 refs., 16 figs., 24 tabs. (ERA citation 13:045100)