Lead in Urban Soils: Studies on Mitigating Health Risks.

Lead contamination is widespread in urban soils all over the world. This issue is increasingly presenting significant health risks to urban populations, partially due to recent increases in human-urban soil interactions through nature-based sustainability projects. Examples include urban agriculture, production of green spaces for living and recreation, green infrastructure, and redevelopment of previously vacant lands. Lead can enter the human body mainly through two different pathways: direct exposure to soil/dust while working/playing in or near contaminated soil, and consumption of produce grown in soils compromised by Pb. Here we present several case studies in New York City, and suggest effective and affordable strategies for soil Pb risk reduction. Our study found that Pb in most vegetables is dominated by contributions from trapped/adhered soil particles, whereas uptake of Pb is much less important. Fruit crops usually have the lowest Pb concentrations and can be safely consumed. Leafy greens and root vegetables may be associated with higher concentrations. Rigorous washing and peeling of the vegetables can reduce Pb levels, and proper selection of vegetable type is critical when soil is contaminated by Pb. Measures to control dust and splash can effectively reduce vegetable Pb concentrations, and can reduce direct exposure through incidental ingestion and inhalation. Some examples include surface cover with compost, wheat straw, mulch, and clean soil. Keeping soil moist through drip irrigation, which is a technique used to conserve water, can also be effective. Mixing compost with soil not only can dilute soil Pb concentrations, but can also improve soil aggregation and reduce soil dust and splash. Through the NYC Clean Soil Bank Program, compost mixed with pristine glacial sediments – both materials previously considered waste – proved to be an effective vegetable growing medium and can be used to build raised beds for contaminated gardens.