Research & reports

Maud Chalmandrier, Marine Canavèse, Yves Petit‐Berghem, Élisabeth Rémy · HAL (Le Centre pour la Communication Scientifique Directe) · Global

This study, using case studies of public action and gardeners' relationships with urban soil, argues that the concept of "urban agriculture" smooths over inherent tensions to promote its development as an action category. This approach tends to minimize differences in meaning among actors regarding their cultivation practices and, critically, relegates the crucial question of urban soil quality and its suitability for food crops to a secondary concern.

Seyedardalan Ashrafzadeh, Niklas J. Lehto, Gareth Oddy, Ron G. McLaren, Ling‐Fen Kang, Nicholas Dickinson, Johannes Welsch, Brett Robinson · Applied Geochemistry · New Zealand (Christchurch)

A study in Christchurch, New Zealand, measured heavy metal (HM) concentrations in suburban garden soils and soils at risk of HM contamination due to former land uses or nearby activities. HM concentrations in suburban garden soils were higher than normal background levels, with 46% of urban garden samples exceeding the residential land use national standard for lead (210 mg kg−1), and the most contaminated soil reaching 2615 mg kg−1. Arsenic and zinc also exceeded national standards in 20% of soils. These findings suggest that soil HM concentrations should be key criteria when determining future land use for former residential areas demolished due to the 2010 and 2011 earthquakes, and that redeveloping these areas as parklands or forests would result in less human HM exposure than agriculture or community gardens where food is produced and bare soil is exposed.

Dorothy Menefee, Ganga M. Hettiarachchi · · United States

Soil contamination with potentially toxic trace elements and anthropogenic organic pollutants is a widespread problem in urban areas worldwide. While urban agriculture increases food security, potential risks exist without knowledge of urban soil contamination. Lead (Pb) contamination is a widespread and common urban soil issue associated with human health risks, with almost half of US EPA Superfund sites having Pb contamination. Cadmium (Cd) is also a widespread urban soil pollutant, largely from industrial activities like plastic manufacturing, battery disposal, and metal ore processing. The bioavailability of soil Pb to humans is unusually low and generally tied to Pb speciation.

Bethany B. Cutts, Jonathan London, Shaina Meiners, Kirsten Schwarz, Mary L. Cadenasso · Local Environment · Global

This paper applies a dynamic spatial politics framework to interpret a 30-year conflict over an urban garden in Sacramento, California. It examines how urban gardens, often idealized, are also sites of conflict due to competing visions of "soil" versus "dirt." The study highlights that contaminants like lead in the soil contribute to this instability, reframing fertile soil as dangerous dirt, and influencing the garden's transformation from a countercultural space to a gentrified amenity.

Sydney Giacalone · Journal for Undergraduate Ethnography · United States (Boston)

This ethnographic study, conducted in Boston and Somerville in the summer of 2016, investigated how urban chicken keeping might transform keepers’ thinking about food systems and animal relationships. The research revealed the unexpected discovery of lead contamination in urban chicken flocks in the Boston area, which unsettled the imagined simplicity of urban agriculture and exposed a "metabolic rift." This finding prompted keepers to engage more deeply with the history of the soil and opened new ways of thinking about collective metabolism, multispecies living, and food politics.

Elizabeth A. Miernicki · Illinois Digital Environment for Access to Learning and Scholarship (University of Illinois at Urbana-Champaign) · United States

A study from the University of Illinois at Urbana-Champaign, USA, that identifies soil contamination as a universal concern in urban agriculture and notes that the long-term benefits of alternative soil management systems such as raised beds have not been explored in the scientific literature. Its stated objective is to determine the effects of six soil management options - direct soil with synthetic fertilizer (DSF), direct soil with organic amendments (DSO), raised-bed mixture with synthetic fertilizer (RBMF), raised-bed mixture with organic amendments (RBMO), raised-bed compost-only with synthetic fertilizer (RBCF), and raised-bed compost-only with organic amendments (RBCO) - on yield of kale, garlic, pepper, cilantro and radish, on soil biological, chemical and physical properties, and on ecosystem services such as water and nutrient retention. Data collected include marketable versus cull yield, soil nutrients and organic matter, soil moisture, weed emergence, infiltration rate and bulk density, but this abstract does not report the comparative results themselves.

Katyelle Rafael, Ariella Andrade Marchioro, Cristiane Maria Colli, Bruna Tiaki Tiyo, Fernanda Ferreira Evangelista, Renata Coltro Bezagio, Ana Lúcia Falavigna-Guilherme · Transactions of the Royal Society of Tropical Medicine and Hygiene · Brazil

This study genotyped Giardia duodenalis in raw-eaten vegetables (crisp lettuce, regular lettuce, kale, chicory, and rocket) sampled from street markets and community vegetable gardens in an urban area of southern Brazil. Researchers analyzed 130 samples from street markets and 130 from community gardens (260 total), washing them in Tween 80 solution, filtering through a cellulose acetate membrane, amplifying the GDH gene by semi-nested PCR, and genotyping positive samples by PCR-RFLP. 7.3% (19/260) of samples tested positive for G. duodenalis, from both street markets (10/130) and community gardens (9/130), including both organic and non-organic products. Assemblage AI predominated, but assemblages B and E, which carry zoonotic potential, were also found. The study concludes this points to a need for investigating commercially sold raw vegetables and establishing stricter quality control.

Richard Blaustein · BioScience · United States

Against a backdrop of heightened concern about lead exposure following the lead-contaminated water supply in Flint, Michigan, a review examines prior research on whether sunflowers (Helianthus annuus) can remove lead from urban garden soil through phytoextraction, in which plants draw contaminant metals up into their shoots. Some preliminary studies suggested sunflowers could phytoextract lead, but more extensive research has been disappointing; adding the chelating agent EDTA raises lead's solubility and plant uptake but is expensive and only meaningful combined with other practices such as compost application. Retired USDA scientist Rufus Chaney states that, unlike successful cases such as alpine pennycress extracting cadmium or canola extracting radioactive cesium, no serious study supports significant lead phytoextraction.

Steve G. Hallett, Lori Hoagland, Emily Toner · Horticultural reviews · Global

This chapter discusses urban agriculture from economic, environmental, and social perspectives, acknowledging differences between urban agriculture in small and large cities, as well as the Global North and South. Urban farms and community gardens can have both positive and negative environmental impacts, such as reducing or increasing energy consumption, improving water infiltration, and beautifying neighborhoods, or producing odors and contaminating water. The chapter also attempts to frame policy recommendations that might help guide urban agriculture's development.

Jennifer C. Latimer, David Van Halen, James H. Speer‬, Stephanie Krull, Patricia G. Weaver, Joseph M. Pettit, Heather Foxx · PubMed · United States (Indiana)

This study collected over 1,061 surface soil samples from an approximately 1.25-acre urban community garden in Terre Haute, Indiana, during the summer of 2012, to evaluate the spatial distribution of lead at the plot level. The results highlighted significant variability in lead concentrations within small areas of a former residential property, with some areas showing high lead concentrations (600 ppm). Based on these findings, several areas of concern were identified, and the community garden was reconfigured to reduce potential lead exposure to gardeners and the local community.

Silvia Mancarella, Giuseppina Pennisi, Daniela Gasperi, L. Marchetti, V. Loges, Francesco Orsini, Giorgio Gianquinto, Gilmo Vianello, Livia Vittori Antisari · Archivio istituzionale della ricerca (Alma Mater Studiorum Università di Bologna) · Brazil (Recife)

This study assessed heavy metal accumulation in an urban garden in Recife, Brazil, at varying distances from a high-traffic road. It found that increasing distance from the street decreased the accumulation of many potentially toxic elements. However, the study revealed a greater human health danger associated with the accumulation of antimony in lettuce, while concentrations of other elements in leaf tissues were within reported thresholds.

Hardiyanto Hardiyanto, Constancio C. de Guzman · Indonesian Journal of Agricultural Science · Philippines (Metro Manila)

This study investigated the levels and distribution of lead (Pb) and cadmium (Cd) in white cabbage, soil, and irrigation water from urban agricultural sites in Las Piñas and Parañaque, Metro Manila, Philippines. Field areas were divided into three sections based on distance from the main road (0, 25, and 50 m), and metal contents were measured by Atomic Absorption Spectrophotometry. The average Pb content (1.09 µg g-1 dry weight) in white cabbage was highest immediately beside the main road, with a similar trend in soil. A negative relationship was found between distance from the main road and Pb and Cd contents in white cabbage and soil. While overall concentrations of Pb and Cd in white cabbage, soil, and irrigation water were within acceptable limits, further study on heavy metal contamination in crops, especially those grown along main roads, was suggested.

Noëllie W. Kpoda, Mariam Sou Dakouré, Boubacar Savadogo, Amadou H. Maïga, Jean-Noël Poda, G.B. Kabre · Journal of Water and Environment Technology · Burkina Faso (Ouagadougou)

This study in Ouagadougou, Burkina Faso, compared the parasitological characteristics of wastewater at a treatment plant's inlet and outlet, and in an open channel conveying treated wastewater to a garden site. Non-viable parasite cysts or eggs were found at the treatment plant, but viable parasite cysts and eggs were detected in the open channel. An epidemiological study demonstrated that open defecation by highly infected individuals within the garden site caused recontamination of the treated wastewater.

Prince Antwi-Agyei, Anne Peasey, Adam Biran, Jane Bruce, Jeroen H. J. Ensink · PLoS ONE · Ghana (Accra)

This study, conducted from September 2012 to August 2013 with 490 respondents in Accra, Ghana, assessed knowledge and awareness of wastewater use in urban agriculture. It found low awareness of irrigation water sources among consumers and street food vendors, and low health risk awareness among farmers, despite high awareness among salespersons and consumers. Crucially, consumers did not prioritize health indicators when purchasing produce, and farmers' health risk awareness did not influence their adoption of safer practices.

Emad Abdulrahman Al-Heety, Kadhim H. Yassin, Safa Abd-Alsalaam · Human and Ecological Risk Assessment An International Journal · Iraq (Baghdad)

This study evaluated the health risk of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) in soils from 14 urban community gardens in Baghdad City, Iraq. The non-carcinogenic hazard index (HI) was below the threshold (HI < 1), indicating no non-carcinogenic hazard. However, the carcinogenic risk index (RI) for Cd, Cr, and Ni exceeded the unacceptable threshold (RI < 1 × 10−4), demonstrating a serious carcinogenic risk for children and adults in the study area.

Kirsten Schwarz, Bethany B. Cutts, Jonathan London, Mary L. Cadenasso · Sustainability · Global

This paper proposes reframing the issue of soil lead contamination and urban gardening in shrinking cities from a potential conflict to a potential solution. Many shrinking cities face high soil lead burdens from their industrial past and the historic use of lead-based paint and leaded gasoline, which is often seen as a barrier to urban agriculture. The paper argues that urban gardening can be a solution to the soil lead problem through soil management, including soil testing and the addition of amendments, and through social network and community building.

Bethany B. Cutts, Danqi Fang, Kaitlyn Hornik, Jonathan London, Kirsten Schwarz, Mary L. Cadenasso · Environmental Justice · United States (California)

This study introduced a Qualitative Historical Geographic Information System (QHGIS) method to investigate how newspapers reflect changing meanings of place in relation to environmental burden and benefit. Applying QHGIS to urban gardening and soil lead issues reported in Sacramento, California, the method revealed the distribution of public narratives of environmental concern across the city, the politics embedded in location names, place name-changes, and how locations serve as framing devices for environmental concerns.

Sheri L. Johnson, Dalila Cardona, J. H. C. Davis, Benjamin Gramling, Chelsea Hamilton, Ray G. Hoffmann, Sabrina J. Ruis, Douglas J. Soldat, Steve Ventura, Yan Ke · Progress in community health partnerships · Global

This study used community-based participatory research to explore backyard gardening practices and soil lead concentrations in urban neighborhoods. Interviews with 20 adult gardeners revealed perceived benefits but few initial concerns about lead exposure, despite children's active involvement. Soil lead concentrations from 17 residential properties ranged from 7 to 3,234 mg kg-1, significantly higher than commercial soils (6 to 13 mg kg-1), indicating a contamination risk.

Andrew Hursthouse, T. E. Leitão, Annette Voigt, Avigail Heller, Béatrice Bechet, Paulo Brito da Luz · HAL (Le Centre pour la Communication Scientifique Directe) · Europe

This chapter overviews factors influencing the chemical, physical, and biological status of soils, water, and the biosphere in urban allotment gardens. It highlights that urban garden soils, water, and biosphere are affected by pollution due to their location in city centers or suburbs, with traffic infrastructure and industrial zones widely identified as impacting soil and water quality. Concerns over long-term risks from pollutant transfer (mainly metals) from soil to plants in these uncontrolled environments have been widely publicized.

Jason Murillo, Environmental Health BCIT School of Health Sciences, Bobby Sidhu · BCIT Environmental Public Health Journal · Canada (Vancouver)

An online survey of 101 community gardeners from 23 community gardens in Vancouver, Canada, investigated perceptions of soil health and contamination. The study found no association between soil testing and garden location, nor between garden location and gardeners' confidence in soil safety. Despite potential health concerns from contaminated soil, community gardeners refrained from soil testing and remained confident in their soil's safety, indicating a gap in safety standards.

Zhongqi Cheng, Anna Paltseva, Ireyena Li, Tatiana Morin, Hermine Huot, Sara Perl Egendorf, Zulema Su, Roxanne Yolanda, Kishan Singh, Leda Lee, Michael Grinshtein, Ying Liu, Kayo Green, Win Wai, Bushra Wazed, Richard K. Shaw · Soil Science · United States (New York City)

This study analyzed trace metal concentrations (Cr, Co, Ni, Cu, Zn, As, Cd, Pb) in 1,652 soil samples from 904 gardens in New York City. It found that many soils exceeded New York State Department of Environmental Conservation's Soil Cleanup Objective (SCO) limits for Pb, Cr, As, and Cd. Specifically, about 21% of community garden samples and 71% of home garden samples exceeded SCO limits for Pb and As, and less than 3% of all samples met criteria for unrestricted use.

Christine Aubry, Jeanne Pourias, Anne Cécile Daniel · HAL (Le Centre pour la Communication Scientifique Directe) · Global

Urban agriculture is gaining popularity, often for its contribution to urban greening, re-establishing connections between urban dwellers and agricultural and food production, and among urban dwellers themselves. However, urban agriculture also involves significant health issues, which advocate for urban planning that promotes its maintenance or establishment under healthy environmental conditions.

Michelle L. Kaiser, Michele L. Williams, Nicholas T. Basta, Michelle D. Hand, Sarah Huber · Journal of Food Protection · 米国・オハイオ

Focus groups (n=67) in four low-income Ohio neighbourhoods plus soil tests at six sites. Residents wanted gardens for fresh produce but worried about soil. Lead, zinc, cadmium and copper were present (paint likely main source); arsenic/chromium and PAHs were low. Further management to cut Pb/Cd bioavailability is needed before food crops; longer-established gardens showed lower contaminant signals. Critical evidence that vacant-lot gardening requires soil risk assessment.

Lydia G. Marquez‐Bravo, Dean B. Briggs, Hannah A. Shayler, Murray B. McBride, Donna Lopp, Edie B. Stone, Gretchen Ferenz, Kenneth G. Bogdan, R. G. Mitchell, Henry M. Spliethoff · Environmental Toxicology and Chemistry · United States (New York City)

A study analyzed 69 soil samples from 20 community gardens in New York City for 23 polycyclic aromatic hydrocarbons (PAHs) and black carbon, sampling both non-growing areas and vegetable-growing beds, including beds with and without visible PAH sources, at each garden. The sum of the US EPA's 16 priority PAHs reached up to 150 mg/kg, with a median of 5.4 mg/kg and mean of 14.2 mg/kg, similar to levels previously reported for urban areas in the northeastern United States. Isomer ratios indicated petroleum, coal and wood combustion as the main sources, and PAH concentrations were significantly and positively associated with black carbon and modeled air PAH concentrations, suggesting a link between historical atmospheric deposition and current soil PAH levels. Median PAH concentration in non-bed areas (7.4 mg/kg) was higher than in beds from the same gardens (4.0 mg/kg) and significantly higher than in beds without visible PAH sources (3.5 mg/kg); beds in gardens with records of soil amendments had 58% lower median PAH concentration than beds in gardens without such records, suggesting that gardening practices in beds without visible sources contribute to reducing soil PAH concentrations.

Brent F. Kim, Melissa N. Poulsen, Jared D. Margulies, Katie L. Dix, Anne Palmer, Keeve E. Nachman · PLoS ONE · United States (Baltimore, Maryland)

This study characterized urban community gardeners' knowledge and perceptions of soil contaminant risks in Baltimore, Maryland, United States, through surveys with 70 gardeners from 15 gardens and interviews with 18 key informants. It found low levels of concern and inconsistent knowledge regarding heavy metal and organic chemical contaminants among gardeners. Furthermore, barriers to investigating garden site history and conducting soil tests, along with limited knowledge of best practices for reducing exposure, were identified.