Preliminary assessment of lead concentrations in topsoil of 100 parks in Los Angeles, California

Los Angeles has a long history of lead (Pb) contamination due to automobile emissions, industrial processes, and Pb-containing paint. Although the amount of Pb coming from these sources has been reduced or eliminated, exposure to Pb-contaminated soil is still a concern. Contaminated soil in urban parks may constitute an important exposure route, since children are particularly vulnerable to the toxic effects of Pb. While the current EPA clean up level is 400 parts per million (ppm) in recreational and residential areas, the Office of Environmental Health Hazard Assessment (OEHHA) of California revised the soil-screening level to 80 ppm, based on a 1 mu g/dL increase of blood level that children experience. In this work, top soil samples in triplicate were taken from each of 100 urban parks in Los Angeles and analyzed to determine Pb concentrations and soil properties. Results show that the average Pb concentration in park soil was 65.5 ppm (range: 0.969-363 ppm), with 35 parks exceeding the California guideline of 80 ppm based on the average Pb concentration measured at each park. Pb concentrations in 42 parks exceeded the background value of 19.7 ppm (by a factor of 3-17). However, variation in measured levels of Pb within most parks was high ( > 10% RSD in 89 parks). Parks containing elevated Pb concentrations in soil were distributed across many areas of Los Angeles, including central Los Angeles, Beverly Hills, Inglewood, and Central Alameda. Children might potentially suffer from an estimated 1-4 mu g/dL increase of blood Pb level according to LeadSpread model. Pb concentrations did not significantly correlate with most soil properties, except for silt (rho = 0.226, p = 0.012). Additionally, soil from sandy loam contained significantly higher Pb concentrations as compared to soil from loamy sand (p = 0.008). Pb concentrations were significantly correlated with park age (rho = - 0.319, p = 0.033) and were generally lower in areas located away from major roads. Monitoring of parks with high levels of Pb as well as investigation of unexamined regions in Los Angeles are needed.