Research & reports

Yvonne Ma, Jessica Chen, Karen Fong, Stephanie Nadya, Kevin J. Allen, Chad Laing, Kim Ziebell, Ed Topp, Laura M. Carroll, Martin Wiedmann, Pascal Delaquis, Siyun Wang · Antibiotics · Canada

Genomic and phenotypic analysis of 55 Shiga toxin-producing E. coli (STEC) isolates of diverse serotypes, recovered from surface waters and sediments in a mixed urban/agricultural landscape in British Columbia, Canada (Antibiotics, 2021), found reduced antibiotic susceptibility across multiple drug classes: florfenicol (65.5%), tetracycline (52.7%), ampicillin (49.1%), streptomycin (34.5%), amoxicillin/clavulanic acid (21.8%), kanamycin (20.0%), ceftiofur (18.2%), trimethoprim-sulfamethoxazole (12.7%), gentamicin (10.9%), chloramphenicol (7.3%), ceftriaxone (3.6%) and cefoxitin (3.6%), while all isolates remained susceptible to ciprofloxacin, nalidixic acid, ertapenem, imipenem and meropenem. Eight isolates (14.6%) were multidrug resistant, and resistance genes including floR, dfrA, sul1/2, tetA/B, aadA, aph, blaTEM-1b and blaCMY-2 were identified alongside multiple plasmid replicon types. The resistance profiles matched those reported in generic E. coli from food animals, and the authors conclude that aquatic environments in the region are a potential reservoir for the maintenance and transmission of antibiotic-resistant STEC, their resistance genes, and associated plasmids.

R. Holm Thomas · Lincoln (University of Nebraska) · United States (Lincoln)

This study investigated remediation strategies to reduce heavy metal uptake in soil from a potential community garden lot near a railroad in Lincoln, NE, where elevated concentrations of lead (Pb) and arsenic (As) were detected. In a greenhouse experiment, romaine lettuce was grown. Biochar amendment resulted in the lowest concentrations of Pb and As in lettuce leaves and stems, whereas coffee grounds amendment led to the highest concentrations across all tested plant parts.

Cleusa Fernandes Ramos, Andréia Assunção Soares, Isabela Carvalho dos Santos, F. Ramos, Odair Alberton, Luciana Kazue Otutumi, Lidiane Nunes Barbosa, Ricardo de Melo Germano, Daniela Dib Gonçalves, Luiz Sérgio Merlini · Journal of Pure and Applied Microbiology · Brazil

This 2020 study in Brazil evaluated the bacteriological quality of six medicinal plants from community gardens, including Cymbopogon citratus and Aloysia citriodora. Analysis of cold extracts revealed bacterial contamination, with Plectranthus barbalus showing the highest aerobic mesophile count and Aloysia citriodora the highest coliform count at 45°C. However, the study concluded that heat treatment (boiling for teas) can significantly reduce or eliminate this bacteriological contamination, making the plants safe for consumption.

Lauren Balotin, Samantha Distler, Antoinette L. Williams, Samuel J. W. Peters, Candis M. Hunter, Chris Theal, Gil Frank, Taranji Alvarado, Rosario Hernandez, Arthur Hines, Eri Saikawa · International Journal of Environmental Research and Public Health · United States (Atlanta)

This study investigated Atlanta residents' knowledge regarding heavy metal and metalloid (HMM) exposures and remediation in urban agriculture, following the detection of industrial slag and hazardous soil contamination in West Atlanta in 2018. Through surveys and follow-up interviews, it was found that participants were concerned about the potential health effects of soil contaminants but unconcerned with produce in their gardens. Gardeners' knowledge of HMM exposure sources and remediation methods was low and varied based on racial group.

Omanjana Goswami, Ashaki A. Rouff · Soil Systems · United States (Newark)

Soils from seven community farms in Newark, New Jersey, USA, were analyzed for lead (Pb) concentration and speciation. Single-step extractable Pb concentration ranged from 22 to 830 mg kg−1, with 21% of samples exceeding the NJDEP limit of 400 mg kg−1 for residential soils. Lowest Pb concentrations were detected in raised beds, while uncultivated native soil and parking lot samples had the highest values. Although most Pb is associated with reducible and oxidizable soil fractions, indicating a lower risk of mobility and bioavailability, Pb exposure through ingestion and inhalation pathways remains a concern when directly handling the soil.

Moisés Savian, Mari Inês Caríssimi Boff, Pedro Boff · Cadernos de Agroecologia · Brazil

This study evaluated Brazilian scientific production from 2009 to 2018 on urban agriculture's contribution to food and nutritional security, analyzing 34 selected articles out of 612. It found that while agrobiodiversity is present in urban agriculture areas, pesticide use is a reality in some crop plots. The research suggests urban agriculture must be based on agroecology to avoid environmental contamination and produce healthy food.

Anna Paltseva, Zhongqi Cheng · RUDN Journal of Agronomy and Animal Industries · United States (New York City)

Elevated trace metal concentrations, particularly lead (Pb), are prevalent in New York City urban soils. This study analyzed the spatial distribution of lead in NYC gardens and assessed pollution levels and ecological risks. Findings indicated that lead posed moderate to significantly high ecological risk, and the majority of NYC garden soils were characterized as polluted.

Candis M. Hunter, Dana Williamson, Melanie Pearson, Eri Saikawa, Matthew O. Gribble, Michelle C. Kegler · Local Environment · United States (Atlanta)

This study used five focus groups with Atlanta community garden leaders to investigate perspectives on composting, hygiene, and mulching, which are practices to reduce exposure to soil contaminants. Gardeners cited a need for more funding, volunteers, and training. A primary barrier to composting and mulching was concern about contamination of source materials, and participants did not directly link these practices to reducing soil contaminant exposure. Hygiene challenges included concerns about beneficial bacteria, inadequate water access, and limited supplies.

Jonas Aleixo da Silva · · Brazil

This qualitative case study analyzed urban agriculture practices in the Mangueira neighborhood, Grajau-MA, Brazil, through visits, observations, and interviews. The study found that while urban horticulture provided benefits like income and product quality, it faced difficulties including reliance on borrowed land, soil depletion, and the use of agrochemical products, indicating that production was not free from chemical fertilizers.

Sara J. Taetzsch, Andrea S. Bertke, Karen Gruszynski · Zoonoses and Public Health · United States (Richmond)

This study investigated the potential overlap between feral cat territories and human-frequented areas in the Richmond metropolitan area, Central Virginia, using GIS. From July to November 2016, 275 feral cats were trapped for TNR clinics. Findings showed that 8.0% of feral cats had the potential to range onto public elementary or preschool property, and 81.5% of those trapped in Richmond City could roam into public parks and community gardens, indicating a risk of zoonotic disease transmission.

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.

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.

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.

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.

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.

B.M. Mercado-Borrayo, Silke Cram Heydrich, Irma Rosas‐Pérez, Manuel Hernández Quiroz, Claudia Ponce De León Hill · International Journal of Phytoremediation · Mexico

In a natural wetland in the Mexico City Metropolitan Area — a major supplier of crops and flowers whose canals hold high concentrations of organochlorine (OC) and organophosphorus (OP) pesticides — bioaccumulation of these pesticides was studied in water hyacinth (Eichhornia crassipes), a plant considered a plague but suggested in the literature to have phytoremediation potential. In vivo bioaccumulation differences for OC pesticides were largely explained by their log Kow, while all OP pesticides showed bioaccumulation regardless of log Kow, and the higher bioaccumulation factors of some accumulated OC pesticides could not be explained by log Kow alone, suggesting passive transport into the plant. Translocation ratios showed water hyacinth to be an accumulating plant with phytoremediation potential for all the organophosphorus pesticides studied and some organochlorine pesticides, and an equation for free water surface wetlands with floating macrophytes showed pesticide removal by the wetland with room for improvement through better management.

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.

Ashley S. Harms, DeAnn Presley, Ganga M. Hettiarachchi, Chammi P. Attanayake, Sabine Martin, Steven J. Thien · Natural sciences education · United States (Kansas City)

This case study examines the decision faced by Mr. John Holloway in Harmony Park, Kansas City, MO, regarding establishing a community garden on a vacant brownfield site in 2009. Concerns arose about soil contaminants on the site, leading to a dilemma about the potential harm versus benefits of gardening in a food desert. The case requires students to evaluate environmental, agronomic, human health, social, and economic issues related to urban soil contamination.

David R. Koenig · BIOS · United States (Sacramento)

This research project, conducted at the University of California, Davis, aims to understand how elevated soil lead levels may affect urban gardening activities in Sacramento, CA. The study investigates the distribution of soil lead levels in the city and how knowledge of this information impacts the local community. Elevated soil lead levels are identified as a potential barrier to urban gardening.

Sam E. Wortman, Sarah Taylor Lovell · Journal of Environmental Quality · United States

This review paper characterized the limited state of scientific knowledge regarding abiotic environmental factors threatening the growth of urban agriculture in the United States. It identified challenges influencing urban cropping systems, including soil contamination and remediation, atmospheric pollutants and altered climatic conditions, and water management, sources, and safety. The development of a science-based approach in these areas is noted as essential for the economic and environmental sustainability of urban agriculture.