Research & reports

J.N. Hogard, Julius N. Fobil, Godfred K. Ofosu-Budu, D. Carboo, Nii‐Ayi Ankrah, Alexander K. Nyarko · · Ghana

This study in Ghana investigated the macro-nutrient content and heavy metal concentrations in solid waste composts to assess their potential for soil fertility amelioration and health implications in urban and peri-urban agriculture. Overall NPK concentration was low, with agricultural waste composts showing higher total N, K, and organic carbon than municipal solid waste (MSW) composts. Heavy metal concentrations for Ni, Zn, Cu, and Cd were generally low and within Australian standards. However, lead (Pb) concentration in mixed MSW composts was significantly high during the dry season, exceeding the Australian limit of 150 mg/kg Pb for unrestricted use. Seasons and composting processes were found to be important determinants of toxic metal concentrations in final compost products.

Bernard Keraita, Pay Drechsel, Flemming Konradsen · Water Science & Technology · Ghana (Kumasi)

A study in Kumasi, Ghana, assessed the use of on-farm ponds to reduce microbial contamination in wastewater-contaminated irrigation water, analyzing over 300 samples. It found that while ponds are common, their potential for pathogen removal via sedimentation is not fully optimized. Helminth eggs reduced by about 70% with careful water collection, but thermotolerant coliforms took six days in the dry season to meet WHO guidelines, indicating suboptimal performance for some pathogens.

Pay Drechsel, Olufunke Cofie, R. van Veenhuizen, Theophilus O. Larbi · Irrigation and Drainage · West Africa

Informal irrigation in urban and peri-urban agriculture (UPA) in West Africa offers benefits but is often hindered by water pollution, threatening public health. A multi-stakeholder process implemented since 2005 in six West African cities, including Accra, Ghana, aimed to integrate UPA into sustainable urban development. However, an internal lesson learned was that local partners may not prioritize every project, and capacity-building efforts might not provide expected incentives for commitment.

Euis Suryaningsih · Jurnal Hortikultura · Indonesia (Bandung)

From January to July 2001, a field experiment on vegetable disease control in a mosaic farming system in periurban agriculture was conducted at a farmer's field in Rancaekek, Bandung, Indonesia. Treatments included white plastic net cages, biorational pesticides, Bacillus subtilis, a mixture of Mancozeb and Bacillus subtilis, and an unsprayed control. All tested alternative control methods were very effective against major diseases of chili pepper, shallot, eggplant, beans, and cucumber, but the use of poisonous synthetic pesticides in periurban agriculture increases the likelihood of contaminating humans and the environment.

Evan Green · · United States (California)

A literature meta-analysis on lead contamination in urban farms was applied to Alemany Farm in San Francisco, California, where soil lead concentrations range from 60 to 720 ppm. It found that every food crop except tree fruits may pose a health risk if grown in Alemany Farm's soil. A phytoremediation plan using Indian mustard (Brassica juncea) to remove lead was found to exceed the farm's available budget, and its timescale made it impractical. The study concludes that phytoremediation is generally not feasible for small-scale urban farms and that other measures are needed to reduce lead exposure for urban farmers.

XU Yong-xian, Biao Huang · Soils · China

A study of a small-scale vegetable farming system in peri-urban Nanjing, China, monitored heavy metal balances and pollution potential from July 2003 to July 2004. Heavy metals entered the soil mainly through fertilization and irrigation, with organic manure application accounting for more than 98% of inputs. Annual heavy metal input in the area was significantly higher than in European farmland, while annual output was very low, under 10% of input, leading to accumulation of heavy metals in the plots; long-term vegetable cultivation had already caused heavy metal buildup in the soils. Copper, lead, zinc, and cadmium concentrations in vegetables and soil were still below national safety standard limits, so the vegetable farming system was assessed as currently safe. However, an evaluation that incorporated atmospheric deposition showed the region carries a high risk of copper, zinc, and cadmium contamination, and the study concludes that intensive vegetable cultivation will aggravate soil heavy metal pollution, potentially pushing the soil to Second Grade of the National Soil Environment Quality Standard within several decades.

Do Thuy Trang, Kåre Mølbak, Phung Dac Cam, Anders Dalsgaard · Tropical Medicine & International Health · Vietnam (Hanoi)

A cross-sectional study in a peri-urban area of Hanoi, Vietnam, surveyed 400 agricultural households and examined 807 stool samples from 620 adults and 187 children for helminth infections. The study found that 39% of samples were infected with helminths, with Ascaris sp. at 21.6%, Trichuris sp. at 9.8%, and hookworm at 21.8%. Wastewater exposure was not a major risk, but lack of sanitation facilities and use of fresh or inadequately composted human excreta in agriculture were important risk factors for infection.

Barbara Matthys, Andres B. Tschannen, Norbert T. Tian‐Bi, Hermann Comoé, Salia Diabaté, Mahamadou Traoré, Penelope Vounatsou, Giovanna Raso, Laura Gosoniu, Marcel Tanner, Guéladio Cissé, Eliézer K. N’Goran, Jürg Utzinger · Tropical Medicine & International Health · Côte d'Ivoire

A cross-sectional survey was conducted in urban farming communities in Man, western Côte d'Ivoire, involving 113 farming households (586 individuals) and 21 non-farming households (130 individuals). The prevalences of S. mansoni and hookworm in farming households were 51.4% and 24.7%, respectively. Risk factors for S. mansoni included close proximity to the Kô River, water contact with irrigation wells and ponds, and low education attainment, while risk factors for hookworm included living in smallholder irrigated rice plots or large rice perimeters, using domestic well water, and low socioeconomic status.

Bernard Keraita, Flemming Konradsen, Pay Drechsel, Robert Clement Abaidoo · Tropical Medicine & International Health · Ghana

The effectiveness of low-cost irrigation methods (drip irrigation kits, furrow irrigation, and watering cans) in reducing contamination of lettuce irrigated with untreated wastewater in urban farming in Ghana was assessed. Analysis of 396 lettuce, 72 soil, 15 poultry manure, and 32 water samples revealed that lettuce irrigated with drip irrigation kits had the lowest contamination levels, with an average of 4 log units per 100g fewer thermotolerant coliforms than those irrigated with watering cans. However, drip kits often clogged, required lower crop densities, and restricted other routine farm activities.

F Ortega Sastriques, Rosa Orellana Gallego · Revista ciencias técnicas agropecuarias · Global

In many cities, potable water is expensive, and its availability is limited and will decrease in the future. Urban agriculture is an aspect to consider in this context.

F Ortega Sastriques, Rosa Orellana Gallego · · Global

Due to high prices and limited availability of drinking water in many cities, urban agriculture will require the use of alternative water sources. Groundwater and surface currents near cities are typically polluted, and this paper points out aspects to consider for safe irrigation using sewage water.

Stephanie Buechler, Gayathri Devi Mekala, B. Keraita · Victoria University Research Repository (Victoria University) · Global

This 2006 global study from Victoria University discusses wastewater use in urban and peri-urban agriculture for crop production and aquaculture, noting its role in generating livelihoods and providing cheap produce. However, the study emphasizes that clear policy guidelines and careful research are needed to prevent potential negative impacts on human health and the environment from wastewater reuse.

Astrid Mendez, Paulo Cseri Ricardo, P Jeny Pérez, Callejas Hernández, Osvaldo Campos · DOAJ (DOAJ: Directory of Open Access Journals) · Cuba

This introductory study in Arroyo Naranjo municipality, Cuba, examined the use of Luyanó effluent wastewater for irrigation in urban agriculture. The wastewater was classified as low contamination based on BOD5 and COD values and posed no toxic contamination risk to soil or environment. However, it should not be used without prior treatment for direct consumption crops due to its microbial load. Experimental plots with carrot, radish, and marigold showed high agricultural yields, and radish harvests had no bacterial contamination.

Halidou Koanda · Infoscience (Ecole Polytechnique Fédérale de Lausanne) · Sub-Saharan Africa

In Sub-Saharan Africa, faecal sludge management practices are often financially unviable due to widespread lack of municipal involvement, paucity of legal provisions, and absence of stakeholder coordination. This leads to indiscriminate dumping of faecal sludge in urban areas or its untreated use in urban agriculture. These practices pose permanent and serious health risks and contaminate scarce ground and surface water. This research aims to develop an innovative strategic planning approach for sustainable urban faecal sludge management to minimize public health and environmental risks.

C. Paul Nathanail, Caroline McCaffrey, Naomi Earl, Neil D. Foster, A. G. Gillett, Richard Ogden · Human and Ecological Risk Assessment An International Journal · United Kingdom

This paper describes a deterministic method for deriving Site-Specific Assessment Criteria (SSAC) in the UK for human health risks from chronic exposure to heavy metals, metalloids, and organic substances in soil. The SSAC indicates soil concentrations above which unacceptable health risks may occur, considering standard and non-standard land uses and various exposure pathways. The method is not intended to generate or replace UK Soil Guideline Values, as this is the responsibility of UK authoritative bodies.

Samantha Langley-Turnbaugh, David E. Wilkinson, D. Rocque · Soil Survey Horizons · United States

This study characterized urban soils in a low-income neighborhood of Portland, Maine, that was heavily industrialized in the late 1800s, examining seven pedons for particle size, cation exchange capacity (CEC), base saturation, exchangeable bases, pH, and trace elements (Pb, Cr, Cu, Co, Cd, Ni, Zn, Hg, Ti, Zr). The soils contained numerous artifacts and showed a high degree of horizontal and vertical spatial variability; several trace elements were present at elevated levels, with lead (Pb) the dominant metal in surface horizons (600 mg/kg), and many metals correlated with each other and with iron and aluminum, and some with clay content and pH, though the study concludes that mapping soil units by specific trace element ranges would be difficult given the extreme variability observed.

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.

R. B. Singh · IAHS-AISH publication · India

A study on wastewater management in 300 class-I cities and 23 metropolitan cities in India found that the total wastewater generated is approximately 158x10^8 l/day, with treatment capacity being only 375x10^7 l/day. In metropolitan cities, only 30% of wastewater is treated before disposal, and most cities only have primary treatment facilities. Untreated water is being used for urban agriculture, posing risks to public health and potential surface and groundwater pollution.

Martin Krauß, J. Moering, Walther Amelung · OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · Global

This study aimed to assess whether local soil contamination contributes to PCB contamination in apples (Malus domestica Borkh.) at an allotment garden site, in addition to background atmospheric deposition. The importance of the soil-air-plant pathway for persistent organic pollutants like PCBs has been rarely studied, and it is unknown if volatilization from contaminated soils or deposition of contaminated soil dust is a significant source compared to background deposition. The research sought to clarify this potential contamination route for apples.

F.P. Huibers, O. Moscoso, Álvaro Ocampo Durán, J.B. van Lier · CABI Publishing eBooks · Bolivia

A study examining wastewater use in urban and peri-urban agriculture in Cochabamba, Bolivia. Both vegetable and fodder crops are irrigated with polluted water — diluted or partly treated municipal and industrial sewage — containing high concentrations of pathogens, heavy metals, and salts. In the downstream La Mayca area, where farmers have an agreement with the municipal water and sewerage company, soil degradation has forced them to increasingly replace vegetable crops with more salt-tolerant fodder crops. In other areas around the city, cultivators deny using wastewater and point to nearby wells as their water source, but many of these wells are likely also polluted and do not yield enough water for the irrigated area they serve. Farmers report no specific health problems related to using polluted water, which contradicts reports from local health workers. Because surface water flow and rainfall are low while industrial pollution is high and wastewater treatment capacity is limited, most of the water available to farmers is of poor quality. Options identified for improvement include reducing industrial pollution, increasing treatment capacity, and adopting integrated water management that blends good-quality groundwater with wastewater — but strong traditional water rights, lack of urban planning, and weak institutions are cited as constraints on improving wastewater management in Cochabamba.

Tony Binns, Roy Maconachie, Adamu Idris Tanko · Land Degradation and Development · Nigeria (Kano)

This paper examines health and environmental concerns associated with urban and peri-urban agriculture (UPA) in Kano, Nigeria. Empirical evidence indicates that industrial and domestic toxins are reaching dangerously high levels, leading to significant pollution of soils and water channels. This raises serious questions about the sustainability of UPA and the long-term health implications of toxin exposure.

Ogunyemi Awodoyin, Taliat Opadeji · Emirates Journal of Food and Agriculture · Nigeria (Ibadan)

A 2003 study in Ibadan, Nigeria, investigated heavy metal contamination of Amaranthus cruentus L. grown on domestic refuse landfill soils. Lead (Pb) and Cadmium (Cd) concentrations in soils from four landfill sites and a control site ranged from 110.5 to 678.5ppm for Pb and 2.01 to 3.20ppm for Cd. Metal accumulation in Amaranthus cruentus L. tissues was proportionate to soil Pb concentrations, while Cd levels in crop tissues exceeded soil levels. Crop growth and yield were significantly reduced due to Pb and Cd contamination, leading to the conclusion that Ibadan landfills are unsafe for Amaranthus cruentus cultivation, with heavy metal concentrations in the vegetable tissues much higher than FAO/WHO dietary allowances.

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.

G. B. Luilo, Othman C. Othman · Journal de Physique IV (Proceedings) · Tanzania (Dar es Salaam)

This study measured heavy metal levels (cadmium, manganese, lead, and zinc) in Cynodon grasses near roads in Dar es Salaam City, Tanzania. Mean levels of lead and zinc varied exponentially with distance from the road up to 15m and correlated with average daily traffic, suggesting vehicular sources. For public health reasons, it is recommended that pasture grasses in road vicinities not be used for foraging dairy cattle and goats.

Bernard Keraita, Pay Drechsel, Philip Amoah · Environment and Urbanization · Ghana (Kumasi)

This study in Kumasi, Ghana, investigated the influence of urban wastewater on stream water quality and peri-urban agriculture through interviews and water quality assessments. It found that population increase and underinvestment in sanitation facilities led to large volumes of untreated wastewater entering streams. High levels of faecal coliform were recorded in the city's streams, downstream areas, and on vegetables sold in Kumasi’s markets due to contaminated wastewater.