URBAN SOIL CONTAMINATION: AN OBSTACLE TO SUCCESSFUL URBAN AGRICULTURE

As we move toward a greener economy and more sustainable living, urban agriculture has become a hot trend – not only that self-grown organic produce can save cost for many low-income families, cultivating abandoned lands in backyards also brings a healthier lifestyle and sense of accomplishment. In many cases, school children are encouraged to participate which is undoubtedly an effective education tool. However, it has long been known that urban soils often contain high levels of contaminants. The contaminants can pose a significant health risk to the urban population, especially for those who participate in gardening activities or consume contaminated produce.

In this study a total of 116 garden soil samples from 72 residences and 12 community gardens in New York City were analyzed for heavy metals. Most samples were from northern Brooklyn. Not surprisingly, these soils are heavily contaminated with Cr, Ni, Cu, Zn, As, Cd, Pb. Their levels are highly variable and some of them are 1-2 orders magnitude higher than New York State background. In general, home gardens are much more contaminated than community gardens and northern Brooklyn is much more contaminated than the rest of New York City. Lead, arsenic and cadmium are the top three metal contaminants. In particular, 51% of the samples contain more than 400 ppm of lead (the USEPA standard for playground) and 12% exceed 1200 ppm. Based on guideline values developed by the New York State Department of Environmental Conservation for Brownfield redevelopment, few gardens (4%) are suitable for unrestricted use.

Currently there is no established guideline as to at what metal levels soils are considered safe for gardening. Most people are concerned with elevated toxics in vegetables and fruits grown in contaminated soil, but the risk from inhalation and incidental ingestion of dusts and dirt have likely been underestimated. With increased and extended exposure through gardening activities, the risk is even higher. Since children are often involved and they are the most susceptible, tougher standards should be recommended and Best Management Practices should be followed whenever possible. Greater public awareness campaign, education and expanded soil screening for urban soils are clearly needed at this stage.