The dirt on urban gardens: Some contamination but <br />help is on the way

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John Carberry

Urban gardening gives resource-poor families greater access to fresh and affordable produce and an opportunity to reconnect with their community, but what about soil contaminants? A Cornell pilot study of 44 gardens in New York City shows that less than 10 percent of soil samples tested had more lead than state guidance values.

That's good news, but more work is needed, says a team of scientists, educators, policymakers and practitioners from Cornell, Cornell Cooperative Extension (CCE)-NYC, Cornell's Waste Management Institute and Department of Crop and Soil Sciences, the New York State Department of Health and the New York City Department of Parks and Recreation's GreenThumb. The team is assessing soil and vegetable contaminant levels in gardens in New York City, Ithaca and other New York cities to understand the health risk to people who spend time in urban gardens and to evaluate management strategies to reduce potential health risks.

"We just do not know the extent of soil contamination in many urban areas, and contaminants can pose health risks, especially in children, through skin exposure, inhalation or when ingested," said Gretchen Ferenz, a CCE-NYC senior extension associate and co-investigator on a four-year, $1.25 million grant from the National Institutes of Health and the National Institute of Environmental Health Sciences to undertake the Healthy Soils, Healthy Communities project.

The pilot study found that for lead levels, more than 90 percent of the soil samples fell below the 400 parts per million (ppm) guidance value set by the state's Department of Environmental Conservation for soil on a residential site. In 12 of the 44 gardens, levels of contaminants were below guidance values in all soil samples tested, reports Murray McBride, director of the Cornell Waste Management Institute, professor of crop and soil sciences, and principal investigator.

In many cases where results exceeded the guidance values, only one or two of 11 samples taken from each garden were excessive, and they were often in samples collected from the ground rather than from beds used to grow food. Gardens with raised beds -- common in urban gardens -- had fewer and lower levels of contamination. A few gardens had elevated contaminant levels at multiple sampling sites. Those gardens have been prioritized to receive soil deliveries from GreenThumb.

"Research is under way in the laboratory, greenhouse and field to determine the best ways to reliably test soils for metals such as lead, arsenic and cadmium, to measure potential for these metals to transfer into different vegetable and fruit crops, and to assess simple and inexpensive management approaches to reduce metal transfer into edible crops," said McBride.

Once the team determines the extent and type of contamination in urban gardens and assesses the risk, it will translate these research findings into practical strategies to reduce exposure to soil contaminants and potential risks. It also will survey GreenThumb gardeners about their gardening activities.

"Given the many benefits of gardening and eating fresh fruits and vegetables, it's important for people to take action to address concerns about soil contamination. Our project will help provide the science-based resources communities need to be proactive and make informed management decisions that are best for their gardens," said Hannah Shayler, extension associate with the Cornell Waste Management Institute, which has issued fact sheets on soil quality.

Meanwhile, CCE-NYC educators and the project team have been holding public forums and workshops, and convening an advisory committee of gardeners, soil scientists, and nonprofit and agency representatives to provide input.


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