Research & reports

Amos Tomiwa Afolabi, Bridget O. Odiyi, Oluwasheun Johannah Ojeniyi · Discover Soil. · Nigeria (Ado-Ekiti)

A study in Ado-Ekiti, Nigeria, investigated heavy metal accumulation in Amaranthus hybridus and Ocimum gratissimum grown on soils from two automobile workshops. A. hybridus accumulated higher metal concentrations than O. gratissimum, with stems showing greater accumulation than leaves. While non-carcinogenic and total cancer risks were within acceptable limits, children showed higher vulnerability, indicating that continuous monitoring and soil remediation are essential for sustainable urban agriculture in these contaminated areas.

Michael J. Ormsby, Luke Woodford, James Joseph Mwesiga, Winnie Ernest, Dativa J. Shilla, Daniel Abel Shilla, Richard S. Quilliam · Environmental Pollution · Africa

This study investigated plastic debris as a reservoir for multidrug-resistant (MDR) enteric bacterial pathogens at two peri-urban agricultural sites in Dar es Salaam, Tanzania. Analysis of 140 environmental samples (soil, water, vegetation, plastic debris) showed higher concentrations of culturable pathogens on plastic debris, with presumptive E. coli loads of ~1 × 10^3 CFU per piece. Plastic debris harbored a greater proportion of MDR strains, including E. coli and K. pneumoniae resistant to critically important antimicrobials, indicating that plastic waste facilitates the survival of MDR pathogens and poses health risks.

Adnan Sirage Ali · Discover Public Health · Ethiopia

A comparative cross-sectional study of 315 urban vegetable-farming households along the Akaki Rivers in Ethiopia used structured questionnaires, multivariable logistic regression, multilevel mixed-effects models and bootstrapped mediation analysis. Two-week diarrhea prevalence was 11.4% (36/315) among children and 8.7% among adults; in this cross-sectional design, which cannot establish causality, wastewater irrigation was associated with more than double the odds of diarrhea (AOR=2.10, 95% CI 1.30-3.40), frequent contact with irrigation water with 80% higher odds (AOR=1.80), and regular raw-vegetable consumption with 60% higher odds (AOR=1.60). Handwashing with soap (57% risk reduction), bathing after farm work (41% reduction) and household water treatment (45% reduction, AOR=0.55) were protective, clustering by irrigation site was modest (ICC about 6%), and hygiene practices mediated 28% of the exposure-outcome relationship.

Aminu Zakariyau, Murtala Rabiu · International Journal of Advances in Engineering and Management · Nigeria (Katsina City)

The potential ecotoxicological impacts of municipal solid waste compost (MSWC) on soil, plants, and humans in urban Katsina, Nigeria, were assessed. Analysis of soil mixtures and plant biomass (maize and beans) revealed high phytotoxicity in beans, while maize considered MSWC as phytonutrients. No statistical difference in non-biodegradable substance concentrations in soils and plants was found, and ecological risk index (ERI) indicated low risk; however, Target Hazard Quotients (THQ) suggested a likelihood of non-carcinogenic effects to the ecosystem.

Taffere Addis, Sisay Ketema, Abayneh Melaku · Frontiers in Water · Ethiopia (Addis Ababa)

This study in Addis Ababa, Ethiopia, investigated trace metal levels in sediment, soil, and irrigated vegetables from farms along the Akaki River, evaluating public health risks. Sediment levels of arsenic, chromium, copper, nickel, lead, and zinc exceeded threshold effect levels. Soil levels of arsenic, chromium, copper, manganese, and zinc exceeded typical world soil values, with nickel at one site exceeding EEC limits for agricultural soils. Critically, arsenic, lead, and zinc levels in some vegetable samples were above WHO allowable limits, despite soil levels being acceptable, and cadmium was the most accumulated metal in vegetables.

Doreen N. Meso, Enos W. Wambu, Gelas Simiyu, Shem M. Mwasi, Thomas Munyao · Discover Environment · Kenya (Kakamega Town)

This study assessed heavy metal pollution in agricultural soils, water, and pumpkin leaves from 21 sites across three zones in peri-urban Kakamega Town, Kenya. It found cadmium pollution in all water samples, and lead and nickel pollution in sections of soil and leafy vegetable samples. Lead pollution was linked to vehicular emissions near the town center, while cadmium enrichment in informal settlements implicated inadequate waste management. Sequential extraction showed 31–35% of soil cadmium was in exchangeable fractions, posing a risk of bioavailability, highlighting persistent heavy metal contamination with implications for public health, environmental sustainability, and agricultural productivity.

Mwangi Kamau, Wanjiku Otieno · International Journal of Veterinary Sciences and Animal Husbandry · Kenya

This study characterized the physicochemical quality of untreated wastewater from three small-scale slaughterhouses on the outskirts of Nairobi, Kenya, and measured its effect on soil microbiology at 0, 50, and 200 meters from the discharge point during both wet and dry seasons. Wastewater biochemical oxygen demand (BOD5) ranged from 1,840 to 2,620 mg/L and chemical oxygen demand (COD) from 3,410 to 4,870 mg/L, exceeding Kenyan discharge standards by 6- to 10-fold. Total bacterial counts in soil at the discharge point were 2.7 times higher than at 200 m (p<0.001), and total coliform counts were 4.1 times higher (p<0.001). The Shannon-Wiener diversity index rose significantly with distance from the discharge point (1.42±0.14 at 0 m vs. 2.34±0.18 at 200 m; p<0.001), indicating that wastewater irrigation selects for a less diverse, coliform-dominated soil microbial community. Seasonal variation was significant for BOD5 and coliform loading but not for the diversity index.

Abubakar Mohd Habu, Ali Sanusi Hassan, Adeniyi Olarewaju Adeleye, Michael Edet Nkereuwem, Ijanu Emmanuel Madu, Garba Barde Bate, Olukemi Adeleye, Usman Mohammed Isah · Biological Environment and Pollution · Nigeria

This study assessed heavy-metal accumulation and non-carcinogenic health risks in commonly consumed leafy vegetables -- lettuce, spinach, and cabbage -- cultivated with wastewater in Zawaciki, Kano State, Nigeria. Vegetable and rhizospheric soil samples were analyzed for cadmium, lead, chromium, nickel, zinc, and copper using atomic absorption spectrophotometry, and bioaccumulation factors (BAFs) were calculated as the ratio of metal levels in plant tissue to soil. Metal concentrations varied significantly across the vegetables (p < 0.05), with lead in lettuce leaves exceeding the FAO/WHO permissible limit by more than 120 times; chromium in cabbage reached 32.22 mg/kg, while lettuce showed elevated zinc (19.83 mg/kg) and copper (9.26 mg/kg). Hazard-quotient risk assessments found HQs for chromium and lead both exceeding 1, and the cumulative hazard index exceeded 1 for all vegetables, reaching its highest value of 18.861 in lettuce.

Stefania Lovo, Samantha Rawlings · The World Bank Economic Review · Ghana, Nigeria

This study investigated the impact of e-waste dumping sites on neonatal and infant mortality, focusing on two major dumpsites in Ghana and Nigeria. Using a difference-in-differences approach, outcomes were compared for children born near and far from dumpsites before and after their creation. E-waste sites increased neonatal and and infant mortality for those living closer to the sites, with event studies suggesting effects emerge two to three years after site openings. There is suggestive evidence that contamination of water and of urban farming produce are among the drivers of the observed effects.

Hailekiros Tadesse Tekle, Desta Berhe Sbhatu, Gebreselema Gebreyohannes · H2Open Journal · Ethiopia (Mekelle)

A study in Hadnet district, Mekelle, Ethiopia, assessed heavy metal concentrations in wastewater, spring water, and three leafy vegetables (lettuce, spinach, cauliflower). Wastewater samples from four experimental sites exceeded permissible limits for 4 out of 10 heavy metals (Cd, Cr, Cu, Mn), and spring water from a comparison site also exceeded limits for 4 metals (Al, As, Cd, Cu). Leafy vegetables grown in the least contaminated experimental site showed high concentrations for 6-7 out of 10 heavy metals, with lettuce and spinach having elevated levels of As and Al, respectively. The study concluded that the wastewater used for irrigation is not safe, the farm soils may have accumulated significant heavy metals, and the cultivated vegetables are highly contaminated, necessitating regulation of wastewater use for irrigation.

ke Chinelo Gloria, Eze H.C, Obasi C.J, Euphemia Afoma Ikegwuonu, Okonkwo Ngozi Nonyelum · International Journal of Research Publication and Reviews · Nigeria

To evaluate the water quality of the Obibia River in Amawbia, Anambra State, Nigeria, water samples were collected monthly and assessed for bacteriological and physicochemical parameters. The study identified multiple bacterial isolates, including Escherichia coli, Klebsiella pneumoniae, Salmonella enterica serovar Typhi, and Vibrio cholerae. Notably, E. coli, S. Typhi, and V. cholerae were frequently observed in both rainy and dry seasons. These findings suggest the necessity of adequate treatment before use and periodic evaluation of the water's quality for drinking and urban agricultural purposes.

Gizaw Ebissa, Aramde Fetene, Hayal Desta · City and Environment Interactions · Ethiopia

Treated wastewater from the plant serving Bole Lemi Industrial Park (BLIP) in Addis Ababa, Ethiopia was sampled at the treatment plant's influent and effluent and analyzed using a treated wastewater quality index (TWWQI) to assess suitability for urban irrigation agriculture. The aggregate TWWQI classified the water as 'very poor' for urban irrigation agriculture, with heavy metals contributing 85% of that grade, nutrient load 4%, salinity 8%, and miscellaneous contaminants 4%. Discrete indices varied: heavy metals scored 'very polluted', nutrients 'excellent', salinity 'poor', and miscellaneous contaminants 'good'. Contaminant removal efficiency ranged from 30% to 100% (58% in aggregate), and some contaminants showed higher concentrations in the effluent than the influent, indicating the treatment plant failed to remove them. Cr3+, Cl− and TDS contributed most to the poor rating, and the plant was found to need upgrading to increase removal efficiency.

Arcadius Martinien Agassin Ahogle, Sammy Letema, Gertrud Schaab, Veronica Ngure, Abraham R. Mwesigye, Nicholas Kibet Korir · Frontiers in Soil Science · Kenya (Nairobi)

This study assessed heavy metal and trace element contamination risks in peri-urban farmlands in Nairobi city catchment, Kenya, by analyzing 60 soil samples from ten vegetable farming zones. Results showed elevated concentrations of elements including As, Cd, Mn, Pb, and Zn, with some exceeding permissible agricultural thresholds. As, Cd, Hg, and Pb exhibited high ecological risks, with Cd contributing 46-66% of the overall risk.

Adane Sirage Ali, Sirak Robele Gari, M.L. Goodson, Claire Walsh, Bitew K. Dessie, Argaw Ambelu · PLoS ONE · Ethiopia

This cross-sectional study investigated the prevalence and risk factors of diarrhea among children under five in 402 wastewater irrigation farming households in Addis Ababa, Ethiopia, from November 2021 to February 2022. The overall prevalence of diarrheal cases in children under five was 22.3%. Diarrhea was strongly associated with wastewater-related occupational exposure factors, including body washing with irrigation water, contaminated cloth with irrigation water, use of protective clothing during farm work, use of farm work cloths at home, and bringing unwashed farm tools home.

Clemêncio Nhantumbo, Nídia Cangi Vaz, Mery Rodrigues, Cândido Manuel, Sífia Rapulua, Jéssica Langa, Hélio Nhantumbo, Dominic Joaquim, Michaque Dosse, José João Sumbana, Ricardo Santos, Sílvia Monteiro, Dinis Juízo · Water · Mozambique

A study investigated fecal microbial contamination levels in river water, drainage water, and drinking water in the Infulene River Basin, Mozambique. Samples from the Infulene River and drainage showed 82% positive for Total Coliforms and 61% for Escherichia coli, while drinking water samples were 63% positive for Total Coliforms and 23% for Escherichia coli. The study confirmed a high vulnerability to microbial contamination across all investigated sources due to poor sanitation and a lack of drainage infrastructure.

Yosef Abebe, Mulugeta Gashaw, Asenake Kefale, Tim Brewer · Water Reuse · Ethiopia

A study on wastewater governance in the upstream catchment of the Awash Basin, Ethiopia, found that untreated wastewater discharged from industries is polluting rivers and the surrounding environment. Regulatory bodies have done little to enforce rules and directives for wastewater regulation, and due to poor implementation of laws, urban agriculture is expanding without concern for its negative health and socioeconomic impacts.

Njenga John Ng’ang’a, Mukundi John Bosco, Masinde Peter Wasike, Kihurani Agnes Wanjiru · Journal of Agriculture Science and Technology · Kenya (Nairobi)

A study in Nairobi's eastern zone assessed heavy metal occurrence in urban farm inputs and food crops (tomatoes, arrowroots, kales). Cadmium, manganese, lead, and zinc concentrations were analyzed in soil, water, and crop samples. The study found that heavy metal contents, particularly cadmium, manganese, lead, and zinc, were above allowable limits in several crops, and based on FAO/WHO standards, were high for health concern.

Ambroise Dalecky, Madougou Garba, Abdoulaziz Ibrahim Danzabarma, Jonas Etougbétché, Sylvestre Badou, Henri‐Joël Dossou, Ibrahima Sow, Cheikh Tidiane Niang, Ousmane Diene, Idrissa Diallo, Mohamed Seyidna Ali Saghiri, Mohamed El Hady Sidatt, Frank van Steenbergen, Amadou Bocar Bal, Luwieke Bosma, Gualbert Houémènou, Solimane Ag Atteynine, Karmadine Hima, Gauthier Dobigny, Yonas Meheretu · Environnement Risques Santé · Sub-Saharan Africa

The abstract text provided consists only of acknowledgments—thanking Valérie Golaz (INED-LPED), Marc Egrot (IRD-LPED), and the organizers of the international conference "Implementation of public policies and pesticides in the Souths" (PoPPesCI project, on public policies and pesticides in urban agriculture), held in October 2021 in Bouaké, Côte d'Ivoire, for prompting the article's writing. It contains no actual findings or content about rodent proliferation or synthetic chemical rodenticides despite what the title suggests.

Sani Abubakar Mashi, Samuel Yakubu, Sofia Yuniar Sani · Asian Research Journal of Agriculture · Africa

A study in the Kubanni basin of Zaria, Africa, evaluated the quality of wastewater used for irrigating urban agriculture soils. The wastewater contained arsenic, iron, chromium, copper, zinc, manganese, and lead. Although concentrations were generally below Nigeria's permissible limits for irrigation, the study noted the metals' tendency to accumulate in soils, raising concerns about potential heavy metal buildup in irrigated soils and crops.

Michel Shengo Lutandula⃰, Fabien Ilunga Mpanga · The Global Environmental Engineers · Democratic Republic of Congo (or Africa)

In Katuba municipality, Lubumbashi, Democratic Republic of Congo, irrigation water, soil, and harvested amaranth from an area of urban amaranth cultivation were analyzed for chemical and microbiological pollutants. Water and amaranth were polluted on both mineral and microbial fronts, while soil was not; water samples contained Paramecia, Entamoeba histolytica eggs, fecal contamination indicator germs, mesophilic flora, and pathogens including Aeromonas hydrophila and Pseudomonas aeruginosa. Amaranth cobalt concentrations exceeded quality standards and the plants were contaminated with Paramecia, Entamoeba histolytica eggs, Escherichia coli, and Klebsiella planticola, leading to the conclusion that consuming these amaranths poses health risks to the population.

Peter Sanjo Adewale, Sunday Clement Olubunmi Makinde, V. Kusemiju, Olawole O. Obembe · Journal of sustainability and environmental management · Nigeria

This study measured and compared lead (Pb), cadmium (Cd) and manganese (Mn) concentrations in soil and leafy vegetables (Amaranthus hybridus, Celosia argentea, Corchorus olitorius) using atomic absorption spectrophotometry at Urban Expressway Farms (UEF) and Peri-urban Road Farms (PRF) in Lagos State, Nigeria. It found the highest Pb concentration (0.93+/-0.06) in Celosia argentea at UEF, and the highest Cd (0.51+/-0.11) and Mn (0.98+/-0.02) concentrations in Amaranthus hybridus at UEF, with Pb in Celosia argentea 5 m from the expressway and Cd in Amaranthus hybridus 10 m from the expressway exceeding WHO/FAO permissible levels; heavy metal residue levels were driven more by farm location than by vegetable type, and the study calls for regular monitoring to prevent consumption of contaminated leafy vegetables and recommends farmers cultivate fields farther from expressways.

Adugnaw Maru Gezahegn, Fekadu Fufa, Esayas Alemayehu, Abebe Beyene · Journal of Chemistry · Ethiopia (Modjo city)

This study investigated the spatial distribution and speciation of chromium in water, soil, and edible plants in tannery-contaminated areas of Modjo city, Ethiopia. Total chromium in the Modjo River was 20.6 mg L−1 upstream, and soil Cr (III) and Cr (VI) concentrations were found to be higher than guideline values. Chromium concentrations in edible plants were also significantly higher than in control areas, with roots accumulating more chromium than leaves and fruits. It was concluded that water, soil, and edible plants in this area contain chromium concentrations higher than recommended for a healthy environment and human consumption.

Anthony Kamara, Foday Thullah · Journal of Nuclear Technologyin Applied Science (JNTAS) /Journal of Nuclear Technologyin Applied Science (JNTAS) · Africa

A study measured background radiation at the two major dumpsites in Freetown, Sierra Leone — Kingtom and Granville Brooke — which are also used for urban agriculture and where youths scavenge scrap metals and plastics daily. Using a portable Radiagem survey meter and GPS, researchers took 10 in-situ dose-rate measurements at each site. The mean equivalent dose rate was 0.8 mSv/year at Kingtom and 1.1 mSv/year at Granville Brooke; Kingtom slightly exceeded the UNSCEAR permissible limit but stayed below the ICRP limit, while Granville Brooke exceeded both the UNSCEAR and ICRP limits. The study concludes both dumpsites could become unsafe in the near future from cumulative radiation exposure for workers, scavengers and other exposed individuals.

Reuben Nwoye Okechi, Edna Ifeoma Chukwura, Christian Okechukwu Nweke · Journal of Advances in Microbiology · Nigeria (Owerri)

This study, conducted in Owerri, Nigeria from June to December 2019, evaluated the interactive toxic effects of ternary mixtures of sodium dodecyl sulfate (SDS) and divalent metals on Serratia marcescens (SerEW01) from the Otamiri River, a source for urban farming. The study found that both concentration addition (CA) and independent action (IA) models predicted lower toxicities compared to experimentally observed data. The Toxic Index and Model Deviation Ratio indicated a synergistic interaction of SDS and metal ions, resulting in higher combined toxicities than predicted, posing environmental hazards due to co-contamination.

Hillary A. Craddock, Elisabeth Fost Maring, Stephanie Grutzmacher · African Journal of Food Agriculture Nutrition and Development · Ethiopia

A mixed-methods pilot survey of 21 teachers and parents in Debre Berhan, Ethiopia, investigated household agricultural practices to understand foodborne illness risks. The study found that half of respondents using manure applied uncomposted manure as fertilizer, and many kept multiple animal species. This suggests a high risk of pathogen exposure for children and adults through contact with uncomposted manure and animals.