Sources and Pathways of Lead Contamination in Urban Community Gardens in Toledo, Ohio

Abstract

Blood lead levels (BLLs) in children of the Toledo, OH area have been elevated for decades, and numerous studies have linked the issue to soil contamination by lead (Pb) paint and leaded gasoline. Young children below the age of 4 years have proven the most susceptible to Pb poisoning due to their high Pb absorption rates and direct ingestion of Pb contaminated sources resulting from instinctive hand-to-mouth behaviors. This problem is significant because high BLLs can result in many pathological and developmental problems including irreversible fetal brain damage, brain damage to the developing prefrontal cortex, behavioral problems, violence, learning disabilities, and more. The objectives of this study were to determine the primary factors leading to Pb and other heavy metals contamination in community gardens in Toledo, OH. A total of 399 samples were collected across 27 community gardens, of which 218 (including soil profiles of 14 gardens) were analyzed for heavy metals using an ICP-OES. Soil profiles were collected down to 40 cm depth (or maximum achievable depth) and subsampled at 5 cm intervals to determine Pb distribution with depth. Using the historical Sanborn Fire Insurance maps combined with the distribution of Pb within gardens across properties, it was found that drip zones, a 1-meter area of soil immediately surrounding structures containing Pb paint, is the main predictor for contamination above the 100 mg/kg action level threshold set by the USEPA (2014). The maps also proved critical for determining the locations of drip zones and other aspects of land use history. Other significant iii factors found to influence soil Pb concentration include proximity to high traffic roads, tilling practices, thickness of garden soil, and garden age. Of lesser importance but still significant was the source of garden soil, presence and quality of liners, and wind transportation of Pb particles. Given the rising popularity of urban community gardens it is more important than ever to understand the sustainability of current gardening practices for minimizing exposure to Pb. Factors effecting garden soil Pb levels in Toledo, OH are universal to many urban areas, consequently these findings are applicable to other cities as well. iv ACKNOWLEDGMENTS Special thanks to the Geological Society of America as well as the Richard D. Hoare award through Bowling Green State University for helping fund this project. Without their financial support this study would not have been possible. Gratitude also goes out to Toledo Grows which provided outreach and the community gardeners who provided access to their gardens. Additional thanks to Blane Houck and Priyanka More for helping with some of the fieldwork. And finally, thanks to Dr. John Farver for providing the idea for this project and advising and guiding me through much of it. His help has been critical and is greatly appreciated. v