A Study in Lead: An Analysis of Lead Exposure in the Old Lead Belt of Southeastern Missouri

Lead mining operations were active in the Old Lead Belt area of Southeast Missouri from the early 1700s until the late twentieth century. The resulting heavy metal pollution in the surrounding areas led the United States Environmental Protection Agency to declare the area a Superfund cleanup site. Lead (Pb) contamination in the environment has the potential to enter human systems through a number of routes and subsequently have a detrimental impact of the health of the affected individuals. This study evaluates the lead concentration in biological samples and assesses routes of Pb exposure for the adult population of Missouri's Old Lead Belt (OLB). Individuals in a known low-lead area in Madison County, Illinois, served as a control group for this study. Lead exposure in both the control area and the OLB was assessed by a questionnaire addressing general lead exposure and hair samples were collected from each individual to evaluate absorbed Pb levels. Soil from individual yards and gardens and vegetable samples were collected and analyzed to evaluate possible routes of exposure to Pb contaminants. The hair, soil, and plant samples were processed by the EPA 3050b acid digestion method, and inductively-coupled plasma mass spectrometry was used to quantify the total concentrations of 204Pb, 206Pb, 207Pb, and 208Pb. It was hypothesized that Pb concentrations would significantly differ in the hair, soil, and vegetable samples between the OLB and the control group, and that the OLB would have higher concentrations in all three sample types. Analysis of variance (ANOVA) was used to test the hair and vegetable samples from both sampling regions and all the soil samples from the OLB. The soil samples from the control group were analyzed using a one-way ANOVA. Linear regression was used to evaluate the isotopic composition of Pb in each sample so that the source of Pb contaminants could be determined. The results of the questionnaires showed a greater number of health symptoms in the OLB group, as well as a significant difference between males and females compared to non-work activities. Overall soil lead concentrations were not significantly different between the OLB and Madison County, which fails to support the hypothesis that concentrations would be greater in the OLB. However, many of the Pb concentrations in the OLB soils exceed the level recommended by the EPA, indicating that remediation efforts may be needed to prevent further exposure. Yard and garden soil samples showed significantly different Pb concentrations, with higher Pb in the yard samples. Lead concentrations in all hair and vegetable samples were below detectable levels, which did not support the hypothesis that concentrations in the hair and vegetable samples would differ between the OLB and the control sites or the hypothesis that the samples from the OLB would have higher concentrations. Linear regression revealed that Pb contamination in the OLB originated from mining activity while the Pb in the Madison County samples came mainly from leaded gasoline. Given the detrimental impact Pb contamination may have on the environment and the organisms living there, it is important to be able to accurately and easily monitor internal levels of Pb as well as be able to locate and minimize the spread of Pb contaminants