DEVELOPING PREDICTIVE TOOLS FOR OPTIMIZING HEALTH CARE USING MEDICAL GEOLOGY: AN EXAMPLE FROM URBAN LEAD POISONING

The intersection between geological sciences and human health, termed medical geology, is gaining significant interest as we understand more completely coupled biogeochemical systems. An example of a medical geology problem largely considered solved is that of lead (Pb) poisoning. With aggressive removal of the major sources of Pb to the environment, including Pb-based paint, leaded gasoline, lead pipes and solder, the number of children in the US affected by Pb poisoning has been reduced by 80%, down to a current level of 2.2%. In contrast to this national average, however, more than 16% of urban children exhibit blood Pb levels above what has been deemed “safe.” We have analyzed the spatial relationship between Pb toxicity and metropolitan roadways in Indianapolis and conclude that Pb contamination in soils adjacent to roadways, the cumulative residue from the combustion of leaded gasoline, is being remobilized. To examine Pb resuspension in more detail, we performed an inter-city study to determine the forcing functions behind a marked seasonal pattern that is observed in children's blood Pb levels. Our hypothesis was that this phenomenon was not just because of behavior, but also because of climatic conditions driving the resuspension of Pb-rich urban dust. We used between 2,300 and about 16,000 blood Pb screening data points from three cities (Indianapolis, Syracuse NY, New Orleans) for monthly average blood Pb values, and regressed these against several independent variables: average monthly soil moisture, particulate matter (PM10), wind speed, and temperature. We found that seasonal trends in children's blood lead levels seems to be controlled by exposure to lead-enriched dust originating from contaminated soils and suspended in the air when several weather related environmental conditions were present: high temperatures, low soil moisture, and elevated fine particulates. Exposure is via increased dust loads in homes and on contact surfaces, with ingestion being the uptake mechanism. These results indicate that the ability of geochemical and meteorological factors to predict blood lead supports the supposition that external loading and exposure drives much of the blood lead concentrations, and provides a valuable tool for health care practitioners in determining the typical average Pb loading to a patient given the snapshot of a single blood Pb test.