Healthy Gardening Research

Healthy Soils, Healthy Communities

Healthy Soils, Healthy Communities¹ is a community-based research project focused on urban community gardens. Our scientists partnered with researchers from:

• Cornell Waste Management Institute,
• Cornell Cooperative Extension, and
• New York City Parks GreenThumb.

We work to help gardeners understand potential risks associated with soil contamination and take action to reduce those risks. The project's research has helped to shed light on the extent and distribution of contaminants in urban garden soils, vegetables, and chicken eggs. Some of the project's results are summarized below.

Soil

We measured levels of lead and other metals in more than 500 soil samples from 54 community gardens. Levels of metals were considerably higher than background levels found in rural soils, but were similar to levels found in other studies of urban soils in New York City and other cities. The results are presented in the journal article, Lead and Other Metals in New York City Community Garden Soils: Factors Influencing Contaminant Distributions.

We also measured polycyclic aromatic hydrocarbons (PAHs) in soil from 20 New York City community gardens. Levels were similar to those from urban soils around the world. The results are summarized in Concentrations of Polycyclic Aromatic Hydrocarbons in New York City Community Garden Soils: Potential Sources and Influential Factors.

Vegetables

We measured levels of lead, cadmium, and barium in soil and vegetable samples from urban gardens in New York City and Buffalo, New York. We found that levels of lead and barium in some urban garden produce were higher than in store-bought vegetables. Levels of lead and cadmium in urban garden produce were generally below health-based guidance values. The results are presented in the journal article, Concentrations of Lead, Cadmium and Barium in Urban Garden-Grown Vegetables: The Impact of Soil Variables.

Chicken Eggs

We measured lead levels in chicken eggs from New York City community gardens and looked at factors that might affect egg lead levels.

While lead was not detected in store-bought eggs or eggs from a rural area, it was detected in about half of the 54 NYC eggs tested in the study, and it was more likely to be detected in eggs from chickens who spent time in areas with higher levels of lead in soil. Because there are no health-based guidance values specifically for lead in eggs, we considered guidance values for lead in other foods. Lead levels in all but one of the New York City eggs were below the food guidance values.

The results suggest that, in order to reduce their own exposure, urban chicken keepers should consider steps to reduce chickens' exposure to lead, including limiting chickens' access to areas with known or suspected soil contamination.

The results are presented in this journal article, Lead in New York City Community Garden Chicken Eggs: Influential Factors and Health Implications.

Garden Exposure to Lead

We assessed lead exposure from multiple pathways for a population of community gardeners and their household members. Urban soils, vegetables and eggs can have elevated levels of lead because of human activities including some industries, past use of leaded gasoline and paint, building demolition and resuspension of dust and soil from nearby areas. Overall, we found that total exposure to lead for the typical urban community gardener and household member was below health-based recommendations. However, some gardeners and even a higher percentage of visiting children were estimated to exceed those recommendations. While healthy gardening practices to reduce lead concentrations in raised beds or other growing areas (such as importing clean soil and amendments) are important and should be encouraged, these practices should be supplemented by other strategies to reduce exposures. The study is summarized in Estimated Lead Exposures for a Population of Urban Community Gardeners.

Footnote

¹ Funded by the National Institute for Environmental Health Sciences' Partnerships for Environmental Public Health program.