Research & reports

Marta Bożym · Ochrona Środowiska i Zasobów Naturalnych · Poland

A study measuring heavy-metal content (cadmium, lead, copper, zinc, nickel, chromium) in compost and resident earthworms sampled from home composters and allotment gardens in the Opole region of Poland. The compost samples themselves were not contaminated with heavy metals and stayed within Polish legal limits for solid organic fertilizers. However, metal accumulation in earthworms varied by metal: the bioaccumulation factor (BAF) was high for cadmium, lead and zinc, while no accumulation was found for nickel, chromium or copper. The authors conclude that earthworm species native to Poland, such as Eisenia fetida, can serve as potential bioindicators of metals in the environment.

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.

Gideon Aghaindum Ajeagah, Chumtchoua Armel Landry, Mbouombouo Mama, Foto Menbohan Samuel, Thomas Njiné · Journal of Applied Biosciences · Cameroon

In lowland areas of Yaoundé, Cameroon, where wastewater is used for market gardening, water samples were collected from November 2013 to April 2014, with identification and bio-statistical analysis conducted in 2015-2016. Flagellated protozoan cysts, identified via Lugol staining after zinc-sulfate flotation concentration, were found at average densities of 101±70 cysts/L for Giardia intestinalis, 34±20 cysts/L for Chilomastix mesnili, 3±6 cysts/L for Retortamonas intestinalis, and 1±3 cysts/L for Enteromonas hominis, with the highest densities recorded during the short rainy season (172±108 cysts/L). Cyst density was significantly correlated (P≤0.05) with physico-chemical parameters including suspended solids, oxidizability, and turbidity. The study concludes that vegetables grown with this wastewater must be well washed, disinfected, and thoroughly cooked before consumption to reduce health risks.

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.

Oscar Díaz Rizo Susana Olivares Rieumont · Anales de la Academia de Ciencias de Cuba · Cuba

This study in Cuba used X-ray Fluorescence and Low-Background Gamma Spectrometry to analyze heavy metal and radioactive element concentrations in marine/fluvial sediments and urban soils. It found heavy metal contamination in coastal sediments of Guacanayabo Gulf, mercury bioaccumulation in oysters from Sagua River estuary, and possible selenium contamination in catfish tissue. The study also reported, for the first time, heavy metal concentrations in urban soils of Havana, Moa, Las Tunas, and Cienfuegos, including in urban agricultural farms, evaluating their quality for urban farming and potential health impacts.

P. Antwi Agyei, Jeroen H. J. Ensink · Journal of Science and Technology (Ghana) · Ghana (Accra)

A study in Accra, Ghana, from September 2012 to August 2013, analyzed 323 soil and irrigation water samples and 501 produce samples for E. coli, and interviewed 693 participants. It found irrigation water was significantly more contaminated than farm soil, and over 80% of produce samples were contaminated with E. coli, with street food salad being the most contaminated. Key risk factors included farm soil, wastewater use, and poor hygiene, while consumers did not prioritize health indicators despite high risk awareness.

Godswill Azinwie Asongwe, Bernard Palmer Kfuban Yerima · Greener Journal of Soil Science and Plant Nutrition · Cameroon (Bamenda)

This study analyzed heavy metal levels (chromium, manganese, lead, cadmium) in 21 urban and peri-urban agricultural wetland soil samples in Bamenda municipality, Cameroon. Average concentrations were 35.73 mg/kg for chromium, 0.08 mg/kg for manganese, 30.64 mg/kg for lead, and 0.45 mg/kg for cadmium. These concentrations were generally lower than the maximum WHO permissible levels.

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.

Kamal Kishore Yadav, Pradeep Kumar Singh, R. C. Purohit · Water science and technology library · India (Udaipur)

A study in the peri-urban area of Udaipur City, India, investigated heavy metal contamination in soil, vegetable crops, and groundwater due to wastewater reuse. While groundwater-irrigated vegetables showed heavy metal levels within WHO limits, wastewater-irrigated spinach, tomato, and radish at site 3 (Kanpur – Madri Villave) exceeded maximum permissible limits for Fe, Zn, and Cd. Urban wastewater-irrigated spinach was found to accumulate Fe, Zn, and Cd significantly above permissible limits at all three selected locations, making it unsafe for human consumption.

Isaiah Sewanu Akoteyon, Adeyemi Davidson Aromolaran · International Journal of Environment and Sustainable Development · Nigeria (Lagos)

This study evaluated peri-urban market gardening and shallow well water quality for irrigation in Lagos, Nigeria. It found that the mean values of bicarbonate, calcium, and pH in shallow wells exceeded detection levels in 66.7%, 60%, and 53.3% of samples, respectively. Salinity and sodium hazard patterns showed that approximately 66.7% of shallow wells had low salinity, 26.7% medium, and 6.7% high.

Joshua Oluwole Olowoyo, Gladness Nteboheng Lion · South African Journal of Science · South Africa

This review reports on the concentrations of trace metals in crops, including leafy vegetables, harvested from various urban areas. It highlights the presence of trace metals in leafy vegetables and discusses various pathways of uptake, possible health risks associated with urban farming, and morphological and physiological impacts of trace metals in leafy vegetables.

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.

Kafeel Ahmad, Zafar Iqbal Khan, Asma Ashfaq, Ameer Khan, Hazoor Ahmad Shad, Mujahid Sher, Zahoor-ul-Hassan Dogar, Ijaz Rasool Noorka, Sumaira Yasmin, Vincenzo Tufarelli, Eugenio Cazzato · The Philippine Agricultural Scientist · Pakistan

This study analyzed heavy metal and metalloid levels in soil and cabbage (Brassica oleracea) from two urban farming sites in Sargodha, Pakistan, irrigated with wastewater. Findings showed that mean concentrations of arsenic (As) and cadmium (Cd) in soil, and manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), cadmium (Cd), and lead (Pb) in cabbage, exceeded permissible limits at both sites. Significant differences were observed in metal and metalloid levels in vegetable samples between sites.

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.

Eduardo De Miguel, Miguel Izquierdo‐Díaz, Amaia Gómez, Juan Mingot, Fernando Barrio‐Parra · Environmental Toxicology and Chemistry · Spain (Madrid)

Forty-two soil samples from seven urban gardens in Madrid, Spain, were collected to measure concentrations of arsenic, antimony, and selenium, along with soil properties. Antimony concentrations exceeded recommended values for agricultural use in 70% of the urban gardens. A human health risk assessment indicated acceptable levels for noncarcinogenic and carcinogenic risks, though carcinogenic values were elevated, with arsenic identified as the main risk driver.

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.

Mujtaba Baqar, Nadia Jamil, Naveed Ahsan, Kiran Khanum, Abdul Qadir, Mariyam Zameer, Anam Khalid · Transylvanian Review · Pakistan (Lahore)

This case study investigated the impacts of heavy metals from wastewater irrigation on soil, groundwater, and leafy vegetables (Indian mustard, spinach, fodder) in the Charrar Drain catchment, Lahore, Pakistan. Samples were collected from seven sites. Drain water showed Cd, Cr, and Pb concentrations exceeding limits at most sites, and groundwater Cd concentrations also exceeded limits, though Cr and Pb were within permissible ranges. Soil samples contained Cd, Cr, and Pb, and leafy vegetables irrigated with wastewater showed varying heavy metal concentrations, indicating a heavy metal bioaccumulation issue that may exceed threshold limits.

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.

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

This cross-sectional study in Accra, Ghana, assessed faecal exposure among 80 farm workers during dry and wet seasons, analyzing water and soil samples for E. coli. The results showed that while irrigation water was highly contaminated (5.6 Log E. coli/100 ml), exposure to farm soil (2.3 Log E. coli/g) was the key risk pathway due to soil-to-mouth events, with 53% of farmers experiencing such events daily. The estimated norovirus infection risk to farmers was found to be higher than guidelines set by the WHO, indicating that exposure to soil is a critical pathway of pathogen risk in wastewater farmers, exceeding recommended health targets.

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.