Research & reports

Christoph Koch, Maria da Glória Arrais Peter · Environmental Challenges · Germany

This citizen science study analyzed inorganic pollutants in private garden soils in central Germany, including front and backyards. Elevated levels of lead and copper were found in one-third of the samples, and zinc in two-thirds. Chromium and nickel concentrations were also elevated in a quarter of the samples, with some readily available substances exceeding limit values.

Izabella Pisarek, Kamila Śmieszkoł, Aleksandra Cichoń, Magdalena Śliwa, Dżoana Latała-Matysiak, Katarzyna Łuczak, Grzegorz Kusza · Journal of Ecological Engineering · Poland

A 2025 study assessed the impact of a railway line on soil quality, particularly heavy metal content, at the "Hutnik" family allotment gardens in Zawadzkie, Poland. Twenty research plots were set out near a forest complex (reference) and near railway infrastructure (a potential emission source), with soil samples collected from a depth of 0-25 cm and analyzed for total zinc (Zn), copper (Cu), lead (Pb), chromium (Cr), and nickel (Ni). Elevated concentrations of copper, zinc, and lead were found in soils close to the railway line, and based on the chemical analysis data, the study concludes that railway transport may pose a greater threat to the environment than previously expected.

Jacek Antonkiewicz, Iwona Paśmionka, Grzegorz Szychowski · Soil Science Annual · Poland

Following a flood that inundated allotment gardens in Nysa, southern Poland, for up to 14 days after the water rose on 14 September 2024, researchers analyzed 12 soil samples collected in early spring 2025 from two allotment garden sites. Most soils were found limed and disinfected, with high organic matter but low total potassium, sodium and sulfur. Zinc and copper concentrations exceeded the average for Polish arable soils, pointing to use of materials enriched with these elements.

Jarosław Chmielewski, Barbara Gworek, Alicja Walosik, Magdalena Florek-Łuszczki · Annals of Agricultural and Environmental Medicine · Poland

Soil (N=196) and root vegetable (N=94) samples from 16 allotment gardens in Warsaw, Poland, were analyzed for manganese, zinc, copper, lead and cadmium and assessed for health risk. Parsley, carrots, beetroots and celery grown in these gardens accumulated elevated levels of all five metals, and the health risk assessment found an increased risk of carcinogenic effects from cadmium and lead in consumers of these root vegetables; the authors conclude consumption of vegetables from the examined gardens should be very limited or eliminated from the diet entirely.

Sabina Rossini Oliva, Rafael López Núñez · Environmental Science and Pollution Research · Spain (Andalusia)

This study evaluated potentially toxic elements (PTEs) in vegetables and topsoils from urban gardens in Seville, Cordoba, Huelva, and a mining area (Riotinto), Spain, comparing them with market and peri-urban samples. Soils in the mining area and cities generally showed higher contamination with As, Cr, Cu, Pb, and Zn compared to other locations. Despite this, all PTE concentrations in vegetables from the studied urban gardens, including those from As-contaminated soils, were below health-based guidance values and market levels (except lettuce), and human health risk assessments indicated safe consumption.

Cosimo Dondini, Xavier Úbeda, Giacomo Certini, Marcos Francos · Journal of Soils and Sediments · Spain (Barcelona)

This study analyzed soils from ten urban gardens in Barcelona, Spain, with a special focus on possible contaminants. Irrigation water was also analyzed, and some of the waters contained a high concentration of salts and nitrites, which are listed as a pollutant. While three tests for heavy metals did not attest to significant pollution, other toxic elements not considered in this study could come from road transport gases or the port of Barcelona. Overall, the soil quality was concluded to be suitable for growing vegetables.

Sara R. Healy, Eric R. Morgan, Joaquín M. Prada, Martha Betson · Food and Waterborne Parasitology · United Kingdom

This proof-of-concept study investigated the presence of Toxocara spp. eggs on 82 'ready-to-eat' vegetable samples (lettuce, spinach, spring onion, celery) from 16 community gardens in southern England. Two lettuce samples tested positive for Toxocara spp. eggs, showing an overall prevalence of 2.4% for vegetable samples and 6.5% specifically for lettuce. This study is the first to demonstrate Toxocara spp. eggs on vegetables grown in community gardens in the UK and Europe, highlighting biosecurity and zoonotic risks.

Michael Hardman, Andrew Clark, Graeme Sherriff · Agronomy · United Kingdom

Using a qualitative approach across the UK's largest urban farm and a range of other urban agriculture (UA) sites, this study examined the barriers to upscaling city farming. Evidence pointed to urban soil contamination and hesitation about growing crops in cities as a core issue preventing UA from scaling up, alongside public hesitancy and financial barriers, despite the practice's potential social, environmental and economic value through job creation, biodiversity enhancement and shorter food supply chains. The paper concludes that public hesitation, financial barriers and soil quality prevent development, and calls for a more pragmatic approach to these barriers.

Marta Crispo, Miriam C. Dobson, Roscoe S. Blevins, William Meredith, Janice A. Lake, Jill L. Edmondson · Environmental Pollution · United Kingdom

Heavy metal (HM) and metalloid concentrations were assessed in 200 urban horticultural soils across ten UK cities. HM were found to be widespread, with most concentrations below UK soil screening values (C4SLs). However, 83% of lead (Pb) concentrations exceeded C4SLs, which is a significant concern. Bioavailable HM concentrations represented a small fraction (0.01–1.8%) of total concentrations, and black carbon (BC) and organic carbon (OC) were suggested to contribute to HM immobilization.

Iwona Makuch-Pietraś, A. Wójcikowska-Kapusta · Land · Poland

This research investigated the distribution, bioavailability, and total forms of zinc (Zn) in soils from domestic and family allotment gardens across six cities in south-eastern Poland. It found that horticultural treatments had a greater impact on sandy soils, and higher Zn contents were present in humus horizons. High values of concentration and Igeo indices indicated significant Zn pollution in these soils, with bioavailable zinc forms being notably high.

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.

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.

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.

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).

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.

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.

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.

Marcelo Ortega Romero, Juan Mingot Marcilla, María Jesús García Martínez, Eduardo de Miguel, Miguel Izquierdo‐Díaz, Amaya Gómez · · Spain (Madrid)

This study evaluated the potential health risk from trace elements in urban garden soils in Madrid, Spain. Thirty-six composite soil samples were collected from the top 20 cm of six urban gardens, and concentrations of cobalt, chromium, copper, nickel, lead, and zinc were determined. The findings indicated that urban soils are significantly enriched in trace elements relative to background levels, suggesting a potential health risk.

Mucig Charlotte · · France

A survey on rainwater harvesting in community gardens in France indicates that while this practice has been ongoing for years, it is poorly documented and faces challenges in adapting to new French regulations. The findings highlight public health issues for both garden users and consumers of fruits and vegetables, as well as environmental and operational concerns.

Zbigniew Ziembik, Agnieszka Dołhańczuk-Śródka, Grzegorz Kusza · Proceedings of ECOpole · Poland

Soil samples were collected from the former "Piast" cement plant within Opole city borders, Poland, and nearby allotment gardens to study radioisotope activity concentrations. Naturally occurring radioisotopes and artificial Cs were found, with K and Cs showing the biggest radioactivity concentration. No significant differences in radionuclide activities were found between soil samples from the former industrial estate and the allotment gardens.

Anna‐Katarina Schilling, Helmut Hotzel, Ulrich Methner, Lisa D. Sprague, Gernot Schmoock, Hosny El‐Adawy, Ralf Ehricht, Anna-Caroline Wöhr, Michael Erhard, Lutz Geue · Applied and Environmental Microbiology · Germany

This study investigated the presence of zoonotic agents in small ruminants kept on city farms in southern Germany, sampling feces and nasal liquid from 48 animals (28 goats, 20 sheep) across 7 city farms and one activity playground. Findings revealed that 100% of sampled sheep and 89.3% of goats carried Shiga toxin-producing Escherichia coli (STEC). Staphylococcus spp. were detected in 75% of both sheep and goats, and Campylobacter spp. in 25% of sheep and 14.3% of goats. Neither Salmonella spp. nor Coxiella burnetii was found.

Cezary Kabała, T. Chodak, L. Szerszeń, Anna Karczewska, Katarzyna Szopka, Urszula Fratczak · Fresenius environmental bulletin · Poland (Wroclaw)

An analysis of 180 allotment garden soils in Wroclaw, Poland, found that concentrations of Cu, Pb, and Zn (12.5-659 mg Pb kg-1, 38.1-2103 mg Zn kg-1, 12.9-595 mg Cu kg-1) were influenced by industrial pollution sources, organic matter, pH, and macronutrients. Soils in gardens on former housing or industrial areas had significantly higher metal concentrations. Up to 35% of soils in the city zone were excessively contaminated, making them unsuitable for vegetable and fruit production and requiring reclamation.

Tanja Pless‐Mulloli, Vivienne S. Air, Catherine Vizard, Ian Singleton, D. L. Rimmer, Philip Hartley · Epidemiology · United Kingdom

A study in an urban, industrial allotment site in the UK's northeast assessed the potential for public health impact related to soil contamination by taking 86 soil samples and analyzing vegetables and eggs. All 18 initial soil samples exceeded UK guidelines for lead (median 869 mg/kg) and arsenic (median 40 mg/kg), and widespread contamination with PCDD/F was also found. Despite high soil contamination, the uptake of lead and arsenic into vegetables and eggs was low, and these were not deemed major exposure pathways.

Tanja Pless‐Mulloli, Karen L. Foster, J Bush · Epidemiology · United Kingdom (Newcastle upon Tyne)

Investigations in Newcastle upon Tyne, UK, analyzed the extent and consequences of disposing 2000 tons of incinerator ash on over forty allotments. Soil, egg, and vegetable samples (75 soil, 21 egg, 65 vegetable) revealed contamination of footpaths with dioxin/furan (max 9000 ng/kg I-TEQ) and high levels of copper, lead, and zinc. Mean dioxin/furan levels in soil were 38 ng/kg I-TEQ and in eggs were 16.4 ng/kg I-TEQ, indicating significant contamination and potential exposure pathways for allotment gardeners and children.

B. Jankiewicz, B. Ptaszyński, Michael Wieczorek · Polish Journal of Environmental Studies · Poland (Lodz)

This study presents the results of lead determination in the soils of six allotment gardens located in various parts of Lodz. Lead was measured spectrophotometrically in the form of pink lead(II) dithizonate.