Research & reports

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.

L.C. Obuseng · Botswana Journal of Agriculture and Applied Sciences · Botswana (Gaborone)

This review highlights the potential for heavy metal accumulation in soil and crops from urban and peri-urban agriculture (UPA) around Gaborone, Botswana, due to the intensive use of chemical fertilizers, pesticides, wastewater, sludges, and industrial effluents. A literature review showed that fertilizers contain heavy metals, and the use of treated or untreated sewage water by UPA farmers can lead to heavy metal accumulation in soil and crops, posing a danger to human health. Information on heavy metal accumulation in soils is limited in Botswana, despite high agrochemical use in UPA vegetable production.

Ariamys Companioni, Jennys Peraza, Zulema Menéndez Díaz, Aileen González, Ledy X López, Ana Elisa Rodriguez, Jorge Cantillo, Fidel Ángel Núñez · Dialnet (Universidad de la Rioja) · Cuba

A descriptive study in La Lisa Municipality, Havana, Cuba, examined 63 Rattus rattus rodents for Angiostrongylus cantonensis infection in an urban farm field. The study found that 46.03% of the captured rodents were infected with A. cantonensis, with infection rates increasing in adult individuals (59.46%) and during the rainy season (55.88%). This demonstrated the circulation of A. cantonensis in its definitive host in the area, indicating an increased risk of transmission to humans.

Surendra K. Pradhan, Olufunke Cofie, Josiane Nikiema, Helvi Heinonen‐Tanski · Sustainability · Global

This research determined the fertilizer value of sawdust and fecal sludge (SDFS) pellets and compared their effect on lettuce cultivation with other fertilizers in a greenhouse and open field. SDFS pellets, with or without enrichments, resulted in higher saleable fresh weight lettuce yields than commercial compost, poultry manure, mineral fertilizer, or no fertilizer. Open field cultivation yielded more than greenhouse cultivation. While no helminth eggs were detected, some fecal coliforms were found in lettuces fertilized with almost all tested fertilizers, including NPK and the non-fertilized control.

Honorine Ntangmo Tsafack, Émile Temgoua, Thomas Njiné · International Journal of Biological and Chemical Sciences · Cameroon

This in situ study in Dschang, West Cameroon, monitored the survival time of E. coli, parasite eggs, and cysts on lettuce, carrot, and eggplant irrigated with polluted urban wastewater for one week. Despite significant E. coli reductions (73-99% over seven days depending on crop and season), E. coli levels on lettuce and carrot remained above health thresholds (10^3 E. coli/g). Positive samples for eggs and cysts ranged from 0-25% on lettuce and carrot, and 0-8% on eggplant, posing a danger to consumers of raw vegetables.

Kouassi Joseph Kouakou, Ahoua Edmond Sika, Seu Jonathan Gogbeu, Koffi Bertin Yao, M. Bounakhla, Denézon Odette Dogbo, Yves‐Alain Bekro · · Africa

This study compared the accumulation potential of five trace metals (cadmium, copper, lead, zinc, and nickel) in lettuce, spinach, and amaranth grown at market gardening sites in Abidjan, Côte d’Ivoire. Using principal components analysis, it was found that lettuce had a greater capacity for accumulating these metals compared to spinach and amaranth. Amaranth and spinach from the three sites showed nearly identical metal accumulation capacities.

Mahantayya V Math, Yashoda R Kattimani, Manjusha M Padhye · Indian Journal of Community Medicine · India (Ahmadabad)

This study points out the impact of wastewater use in urban agriculture on the incidence of diarrhea in Ahmadabad, India. Vegetables grown with wastewater have an increased risk of internalization of food-borne bacteria such as E. coli and Salmonella into edible plant parts, posing a serious health risk. Contaminated water, soil, poor hand hygiene, and improper handling are sources of bacterial contamination for vegetables and fruits.

Alfan Prianggara, Gunanti Mahasri, Abdul Manan · Journal of Aquaculture and Fish Health · Indonesia (Surabaya)

A survey in Surabaya, Indonesia, investigated water quality and endoparasite prevalence in Nile tilapia (Oreochromis niloticus) from urban farming floating cage programs. Water quality parameters were measured, and average endoparasite prevalence was 5.71% for Eimeria spp. and 8% for Acanthogyrus spp. The study found positive correlations between water clarity, ammonia, and DO with Eimeria spp. prevalence, and between temperature, pH, nitrate, and nitrite with Acanthogyrus spp. prevalence, indicating a link between water quality and parasite infection.

Obinna Elijah Nworie, Junhao Qin, Chuxia Lin · Toxics · Global

This study investigated trace element uptake by wild herbaceous plants at a multiple trace element-contaminated site. It found significant variability in bioaccumulation and translocation factors among plant species, identifying some as hyperaccumulators for specific elements. The marked accumulation of trace elements in plant tissues suggests that the site may not be suitable for urban agricultural production.

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).

Baby Shaharoona, Said Al‐Ismaily, Ahmed Al‐Mayahi, Nadhira Al-Harrasi, Ruqaiya Al-Kindi, Abdullah Al-Sulaimi, Hamad Al-Busaidi, Mohammed Al‐Abri · Heliyon · Global

A study in A'Seeb city, Oman, combined a sociological questionnaire survey of residents' perceptions with sampling of pathogenic bacteria, water-soluble metals, basic cations, salinity and texture in soil and groundwater near urban gardens and municipal waste disposal sites. Most surveyed residents were not paying attention to the negative consequences of their activities on soil and the environment. Heavy metal concentrations were significant at some contaminated sites though still below international standards, while fecal contaminants were reported in some garden, waste-site and groundwater samples, identifying human pathogens in risk group 2 including Klebsiella pneumoniae, Shigella spp. and E. coli.

Wojciech Mrozik, Soydoa Vinitnantharat, Thunchanok Thongsamer, Nipapun Pansuk, Pavinee Pattanachan, Parinda Thayanukul, Kishor Acharya, Marcos Quintela‐Baluja, Charles R. E. Hazlerigg, Aidan Robson, Russell J. Davenport, David Werner · The Science of The Total Environment · Asia

A study of three family-owned peri-urban aquaculture operations downstream of Bangkok, Thailand — spanning extensive, semi-intensive and intensive practices — used micropollutant analysis, genetic markers and 16S rRNA amplicon sequencing to assess water quality against aquaculture standards. Canals draining Bangkok did not meet quality standards and were sources of faecal coliforms, Bacteroides, Prevotella, human E. coli, tetracycline-resistance genes and nitrogen entering the ponds, causing algae blooms. The aquacultures in turn discharged salinity and the herbicide diuron into the canals; diuron was detected in shrimp, though not at a level of concern to human health. The extensive aquaculture attenuated an estimated 20 population equivalents of nitrogen pollution and trillions of faecal coliform inputs per year.

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.

Dan Li, Chun Hong Wong, Mei Fang Seet, Nicole Kuan · Frontiers in Microbiology · Singapore

This study conducted, for the first time to the authors' knowledge, an investigation of Stenotrophomonas maltophilia -- an emerging opportunistic pathogen capable of causing high-mortality nosocomial infections in immunocompromised patients while also being ubiquitous in the environment -- on leafy green vegetables and in a hydroponic farming facility in Singapore. Eleven isolates were recovered from three vegetable types (sweet basil, kale, parsley) and the nutrient solution, with high population levels reached in vegetables under abused storage temperatures (over 8-log CFU/ml in basil juice after six days at 20°C) and on hydroponic facilities through biofilm formation (8 to 9-log CFU/well), and UV treatment (over 4-log reduction at 250 mJ/cm²) was identified as an effective measure to reduce contamination in nutrient solutions and facilities.

Anne Barbillon, Christine Aubry, Nastaran Manouchehri · HAL (Le Centre pour la Communication Scientifique Directe) · France

This French guide, "R.E.F.U.G.E.," developed by AgroParisTech, sets out a four-step methodology to help urban-planning actors in the Île-de-France region assess and manage soil contamination risk before establishing urban agriculture on available land: a historical and environmental site study, a sampling strategy, interpretation of soil analyses, and, where warranted, a formal health risk assessment. Based on France's national methodology for managing polluted sites and soils, it is intended as a first harmonized technical tool for the field and was slated for a testing phase applying it to future urban agriculture projects. The abstract itself does not report contamination measurements or findings from any specific site; it describes the assessment procedure rather than presenting soil contamination data.

Timo Falkenberg, Deepak Saxena · Indian Journal of Community Medicine · India (Ahmedabad)

A 12-month case-cohort study of 187 households in four communities of Ahmedabad, India, purposively selected by irrigation water type (groundwater, surface water, wastewater), with bimonthly self-reported health diaries and most-probable-number measurement of Escherichia coli in water. Mean E. coli concentrations per 100 mL were 3.04×10^4 (groundwater), 9.28×10^5 (surface water) and 4.02×10^9 (wastewater) — all exceeding international irrigation water standards. Diarrhoea incidence was 7.92 episodes per 1000 person-weeks in the groundwater area versus 13.1 (wastewater) and 13.4 (surface water), with a positive correlation between irrigation water quality and diarrhoea. Wastewater reuse is often promoted as a water-scarcity fix for urban agriculture; this study shows it carries a health cost borne by the farming households themselves.

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.

Mohamad Assad, Michel Chalot, Fabienne Tatin‐Froux, Valérie Bert, Julien Parelle · Journal of Environmental Quality · Global

This study investigated element transfer in edible crops (cucumber, pepper, cabbage, lettuce) and poplar (Skado cultivar) grown on soils contaminated with sediments dredged from water canals in the 1960s, aiming to develop a biomonitor. The results showed accumulation of cadmium (Cd) and zinc (Zn) in the edible parts of crops, particularly leafy vegetables, indicating that Cd could be ingested in amounts reaching the tolerable daily intake (TDI) in this context. No accumulation of lead (Pb) was detected.

P.S. Bouda, Edmond Hien, A. Dioma, Hyacinthe Kambiré, Yacouba Maïga, Der Adolphe Somé, Sylvie Nazaret, A.S. Ouattara · DOAJ (DOAJ: Directory of Open Access Journals) · Burkina Faso

A study in Ouagadougou sub-urban agricultural fields, Burkina Faso, assessed the impact of using untreated Solid Urban Wastes (SUW) as agricultural fertilizers on soil properties and crop production. SUW amendment significantly increased pH, total C, N, P, and available P, and maize height and biomass yield were 124% and 164% higher in amended plots, respectively. However, trace metal elements (Cu, Zn, Pb, Ni, Cr) concentrations were higher in amended fields, indicating that urban waste carries contaminants posing public health risks.

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.

Piotr Krzyk, Bogusława Kwoczyńska · Problemy Drobnych Gospodarstw Rolnych / Problems of Small Agricultural Holdings · Poland (Cracow)

This study quantitatively assessed the conversion of agricultural land to investment purposes in Cracow's Mogiła and Wyciąże neighborhoods from 2010-2013, based on local plans. It also addressed soil quality, heavy metal content, and pH. Analysis of spatial management plans for these areas indicated a systematic decline in the share of biologically active areas.

Timo Falkenberg, Deepak Saxena, Thomas Kistemann · The Science of The Total Environment · India (Ahmedabad)

A cohort study investigated the contribution of wastewater irrigation to in-household water contamination among urban farming households in Ahmedabad, India, within the context of WASH (Water, Sanitation, Hygiene). Drinking water samples from 204 households were collected four times over 12 months, and E. coli was quantified. Significant positive differences in water quality between point-of-source and point-of-use samples were identified in 78% of households. During the monsoon, the peak of contamination, only 6% of households had access to safe drinking water at the point-of-use. Wastewater irrigation showed an adverse effect on in-household water contamination, with an effect size larger than the mitigation effect of access to sanitation or personal hygiene.