Research & reports

Cecilia Herbón, María Teresa Barral, Remigio Paradelo · Applied Sciences · Spain (Santiago de Compostela)

The concentrations of trace elements Cu, Pb, Zn, Ni, Cr, and As were investigated in 55 urban soils in Santiago de Compostela, northwestern Spain. While most soils showed higher trace element concentrations than regional backgrounds, they were not classified as contaminated according to Spanish regulations. However, geoaccumulation index values indicated low to moderate pollution levels in most soils, with Cu, Pb, and Zn highest in city center green areas, and Cr and Ni linked to parent material lithology.

Chammi P. Attanayake, Ganga M. Hettiarachchi, Mónica Palomo, Gary M. Pierzynski, Blanca Calderón · ACS Agricultural Science & Technology · United States

The effect of limestone and composted manure on lead (Pb) in vegetables and Pb bioaccessibility was assessed in a contaminated urban garden (total Pb ~200 mg kg⁻¹). Amendments did not affect Pb in vegetables or Pb bioaccessibility. Peeling reduced Pb concentration in radish by half, and removing surface dust reduced Pb in leafy vegetables by 40-50%. Daily Pb intake from consuming lettuce and carrot/beetroot from this garden was approximately 1.5 times higher than the interim reference level proposed by the U.S. Food and Drug Administration.

Jonathan Hall, Isabel Shargo, Niya Khanjar, Jianna Howard, Laura Schmidt, Ashley Deng, Camryn Edwards, Isabelle Berman, Joseph Galarraga, Sacoby Wilson · Environmental Justice · United States

This study in Baltimore, Maryland, used GIS mapping and spatial analysis to assess the proximity of urban farms to environmental hazards, including those with heavy metal contamination. Analyses indicated that contamination of urban farms is a possibility due to proximity: more environmental hazards were found in census tracts with urban farms, and low-income communities of color had hazards near urban farms. Historically industrial areas showed a higher concentration of environmental hazards with heavy metal or unknown contamination.

Isabel Shargo, Jonathan Hall, Ashley Deng, Niya Khanjar, Camryn Edwards, Isabelle Berman, Joseph Galarraga, Sacoby Wilson · Landscape Journal · United States (Baltimore)

This study in Baltimore, Maryland, used GIS mapping and hotspot analysis to assess the proximity of urban farms to environmental hazards. Most urban farms were located in low-income communities of color. However, most environmental hazards were not near urban farms but in predominantly White areas or historical industrial centers. Despite a generally low risk of contamination, some urban farms in low-income and Black/African American communities were potentially contaminated by hazardous sites.

Elisabeth Ziss, Wolfgang Friesl‐Hanl, Sophia Götzinger, Christoph Noller, Markus Puschenreiter, Andrea Watzinger, Rebecca Hood‐Nowotny · Sustainability · Europe

In the "Heavy Metal City-Zen" citizen science project, community members in urban gardens in Vienna, Austria collaborated on collecting soil and plant samples to assess heavy metal contamination risk. Trace metal concentrations were generally below guideline thresholds, but at a few garden sites soil concentrations of lead, cadmium and zinc exceeded Austrian recommended limits, and at two sites plant trace metal concentrations exceeded European food standard limits; the project proposes expanding the citizen-led sampling to all of Vienna so new gardens can assess local soil risk before planting.

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.

Joycelyn K. Quansah, Cesar L. Escalante, Angela Parry‐Hanson Kunadu, Firibu Kwesi Saalia, Jinru Chen · Agriculture · Ghana (Accra)

A survey was conducted among 102 urban leafy green vegetable farmers from 12 farming areas in Accra, Ghana, to determine agricultural practices and their association with microbial safety of vegetables produced. It was observed that 70% of farmers used water from waste drains for irrigation, 99% used incompletely composted manure, 96% harvested with bare hands, and over 60% disagreed that polluted irrigation water can contaminate vegetables or make consumers sick. Vegetables cultivated by farmers with no formal education, less food safety knowledge, and those who disagreed about contaminated water causing illness were associated with higher fecal coliform and Enterococcus sp. counts.

Ada Górna, Krzysztof Górny · Miscellanea Geographica · Cuba

An exploratory, classification-based study combining fieldwork with satellite and aerial imagery analysis characterized urban agriculture across the built-up areas of Havana, Cuba. It found urban gardens distributed unevenly across the city, concentrated in lower-density districts where land was intentionally left between buildings by modernist planners, with organopónico (organoponics) as the most common production technique — but found that the material commonly used to build the bordering walls of these plots is asbestos, posing a significant health threat to both producers and consumers.

Małgorzata Ćwieląg‐Drabek, Agata Piekut, Klaudia Gut, Mateusz Grabowski · Scientific Reports · Europe

A study of family allotment gardens (FAGs) in Silesia Province, one of the most polluted regions in Poland, analyzed 219 soil samples and 64 edible plant samples to link the geochemical disturbance caused by past mining and smelting activity to consumer exposure to toxic and carcinogenic metallic trace elements. Contents of these elements in topsoil were spatially diverse and depended primarily on the location of industrial pollution sources. Average cadmium (0.52 mg/kg fresh weight) and lead (0.57 mg/kg fresh weight) content in vegetables exceeded maximum permissible concentrations under European quality standards. A human health risk assessment based on three dietary exposure scenarios found that, in every scenario, potatoes — a staple of the Polish diet — carried the highest average daily dose for all three elements. The study concludes that consuming vegetables grown in Silesia Province's family allotment gardens may pose a significant health risk to consumers.

Pernille Malberg Dyg, Søren Christensen, Corissa Jade Peterson · Health Promotion International · Global

A thematic review of 51 articles published between 1980 and 2017 examined the effects of community gardens on wellbeing among vulnerable populations. Findings suggested positive impacts on physical health and individual/social wellbeing, but food security enhancements were inconsistent. Two articles raised potential food safety concerns in urban community gardens, recommending attention to minimizing these risks.

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.

Miguel Izquierdo‐Díaz, Peter E. Holm, Fernando Barrio‐Parra, Eduardo De Miguel, Jonas Duus Stevens Lekfeldt, Jakob Magid · Journal of Environmental Quality · Global

This study evaluated air pollution in urban green areas using edible plants. Analysis of 36 unwashed leaf samples showed that plants exposed next to roads had higher contents of traffic-related elements, and outdoor samples were enriched in marine aerosol ions. Cadmium and lead concentrations did not exceed European legal maximum levels for vegetables, indicating their consumption would be safe.

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.

Anne Barbillon, Christine Aubry, François Nold, Stéphane Besançon, Nastaran Manouchehri · Agricultural Sciences · France

This study assessed health risks from soil trace metals (lead, cadmium, mercury, copper, and zinc) at three urban farms near Paris (Ile-de-France region), evaluating two main exposure pathways: soil and vegetable ingestion. All three farms had soil trace-metal levels above geochemical background values and the thresholds used in France as reference values for sludge spreading. Using a Hazard Quotient (HQ)-based risk assessment (HQ being the ratio of estimated daily intake to tolerable daily intake), the riskiest scenarios were urban farmers working on-site daily year-round (HQtot = 1.02), child gardeners (HQtot = 1.29), and regular child consumers eating exclusively the farm's vegetables under a maximalist scenario (HQtot = 1.6). The adult gardener scenario followed (HQtot = 0.9), while the lowest-risk scenarios were adult consumers (HQtot = 0.62) and farm workers (HQtot = 0.45).

Abdallah Zacharia, Wajihu Ahmada, Anne H. Outwater, Billy Ngasala, Rob Van Deun · The Scientific World JOURNAL · Tanzania

This cross-sectional study, conducted from February to August 2018, evaluated three waste stabilization ponds (WSPs) in the Morogoro, Mwanza and Iringa regions of Tanzania, where treated effluent is used for urban agricultural activities despite the disease-transmission risks posed by untreated or partially treated wastewater. Using APHA physicochemical methods, the modified Bailenger method and Ziehl-Neelsen staining for parasites, and membrane filtration for fecal coliforms (FC), analyzed with SPSS version 20, the study found helminth egg removal ranging from 80.8% to 100% and protozoan (oo)cyst removal from 98.8% to 99.9%, with the Mwanza WSP showing the highest FC reduction (3.8 log units per 100 mL). Both parasites and FCs in the effluents of the assessed WSPs were found at concentrations exceeding World Health Organization and Tanzania Bureau of Standards limits, except for helminths in the Morogoro WSP and FCs in the Mwanza WSP. FC counts correlated significantly with protozoa (p<0.01) and predicted protozoa occurrence well (p=0.011), with correlations also found among physicochemical parameters, parasites and FC bacteria. The study attributes the systems' inadequate performance to a lack of regular maintenance and/or operation beyond capacity, and concludes that FC indicators are a reasonable proxy for monitoring protozoa but not for helminths, which should be surveyed independently.

Martin Dawson, Mike Hutchins, Nuria Bachiller‐Jareno, Steven Loiselle · Freshwater Science · United Kingdom (London)

A citizen-science study from 2014 to 2016 assessed water quality in a 5.6-ha urban community garden in southwestern London, using borehole water. Measurements of specific conductance and tryptophan-like fluorescence were taken over 28 months. The study found no evidence of external contamination sources or temporal changes in water quality. However, significant variations in water quality between boreholes were directly linked to on-site manure storage and use, and local geological conditions.

Zane Vincēviča–Gaile, William Hogland, Māra Stapkēviča, Juris Burlakovs · Linnaeus Eco-Tech · Latvia

This study investigates the transfer of metallic elements in the soil-plant segment of the food chain through laboratory and field experiments. It also includes a quantitative analysis of food samples from Latvia, including fruits and vegetables from Riga city allotment gardens, to identify element composition and potential contamination risks from urban pollution. Results of experiments and analyses revealed the influence of factors such as seasonality, botanical origin, site-specific factors, agricultural practice, and food processing on element transfer.

Cécile Le Guern, Liliane Jean‐Soro, Béatrice Bechet, Thierry Lebeau, Dorine Bouquet · Land Degradation and Development · France

Urban allotment gardens in Nantes, France, were found to have soil contamination, with lead (Pb) levels ranging from 100–400 mg kg−1, posing health risks. Local actors collaborated to characterize soil, evaluate sanitary risks, and discuss management options. The most frequent solution was replacing polluted soils with clean soils, while other strategies included on-site management of excavated soil, non-accumulative cropping, or changing land use.

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.

John Misenheimer, Clay Nelson, Evelyn Huertas, Myriam Medina-Vera, Alex Prevatte, Karen D. Bradham · Geosciences · Puerto Rico

Total and bioaccessible arsenic (As) and lead (Pb) levels, and their uptake by 10 commonly grown garden plants, were examined in three urban community gardens in Puerto Rico. Total As ranged from 2 to 55 mg/kg and Pb from 19 to 172 mg/kg in soils. Leaves accumulated higher concentrations of As and Pb than edible flesh, with culantro leaves showing the highest concentrations (3.2 mg/kg dw As, 8.9 mg/kg dw Pb).

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.

Milan Geršl · · Czech Republic (Brno)

A study in Brno, Czech Republic, assessed toxic metal levels and soil attributes (pH, ORP, conductivity) in specific allotment garden areas using XRF analysis. Four out of eight metals (Cd, Cu, V, and Zn) exceeded legal norms, with cadmium (Cd) being the most hazardous at 12.69 mg/kg against a legal norm of 0.5 mg/kg. Despite high levels, the mobility of these metals was expected to be low given the detected soil attributes.