Research & reports

Georgette N. Ngweme, Dhafer Mohammed M. Al Salah, Amandine Laffite, Periyasamy Sivalingam, Dominique Grandjean, Konde Nkiama Numbi Joël, Crispin K. Mulaji, Florian Breider, John Poté · The Science of The Total Environment · Africa

This study investigated levels of persistent organic pollutants (POPs) in irrigation water, soil, and Amaranthus viridis from gardening sites in Kinshasa, Democratic Republic of the Congo, to assess environmental and human health risks. A survey of pesticide and fertilizer use was conducted with 740 market gardeners, and POPs (organochlorine pesticides, PCBs, PBDEs, and PAHs) were analyzed in irrigation water and 144 vegetable samples. The highest PAH levels were found in A. viridis at all sites studied; the sum of seven PCB congeners ranged from 15.89 to 401.36 ng/g; chlorpyrifos-ethyl and p,p'-DDE were the predominant OCPs detected; and among PBDEs, only BDE47 was quantified at notable concentration in the plants, with none detected in irrigation water. Higher estimated daily intake values indicated that consuming the leafy vegetables could be associated with increased health risks, though calculated incremental lifetime cancer risk values indicated no potential carcinogenic risk for the local population. The study recommends implementing urban agriculture control programs for POPs and fertilizer use in Kinshasa to protect public health.

· Journal of Animal and Plant Sciences (J Anim Plant Sci ) ISSN 2071 – 7024 · Africa

A study in Port-Bouët, Abidjan, examined market gardeners' phytosanitary practices and pesticide residue incidence on lettuce. It found that 39.6% of pesticides used were not recommended for market gardening, 86.84% of gardeners did not protect themselves during application, and 80.26% did not observe pre-harvest intervals. Consequently, 93.33% of lettuce samples did not comply with Codex Alimentarius and EU standards due to high pesticide residue contamination.

Cosmos C. Alamanjo, Abimbola O. Adepoju, H. Martin, R.N. Baines · Zenodo (CERN European Organization for Nuclear Research) · Nigeria (Jos)

This mixed-methods study investigated farmers' perceptions, willingness, and capacity to use household sewage sludge as organic resources for peri-urban agriculture around Jos, Nigeria. Farmers were found to use a complex mix of fertilizers and were keen to utilize household sewage sludge for soil fertility, though constrained by accessibility. A critical finding was that household sewage sludge observed in the field is heterogeneous due to its proximity to urban refuse disposal, raising concerns for possible cross-contamination of pollutants and indicating a lack of extension guidance.

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.

Desta Woldetsadik, Pay Drechsel, Bernard Keraita, Fisseha Itanna, Berhanu Erko, Heluf Gebrekidan · International Journal of Food Contamination · Ethiopia (Addis Ababa)

An assessment in Addis Ababa, Ethiopia, analyzed 210 lettuce and 90 irrigation water samples for faecal coliform and helminth eggs. Faecal coliform levels ranged from 4.29-5.61 log10 MPN 100 ml−1 in water and 3.46-5.03 log10 MPN 100 g−1 on lettuce, exceeding WHO recommendations. Helminth eggs were detected in 80% of water and 61% of lettuce samples, also exceeding standards. While washing methods reduced contamination, levels remained in a potential risk range.

Ojuolape F. Akande, S. A. Ajayi · International Journal of Environment Agriculture and Biotechnology · Nigeria

This study measured heavy metals (As, Cd, Cu, Pb, Zn) in soil and in amaranth (Amaranthus hybridus) and jute mallow (Corchorus olitorius) vegetables from selected peri-urban farms around Osun State, Nigeria, to assess human health risk. Soil concentrations fell within FAO/WHO (2002) and EU (2006) agricultural background ranges, but vegetable samples showed appreciable metal levels; arsenic was below detection in all samples, amaranth showed higher retention than jute mallow for all metals except copper, the transfer-factor order was Cd > Zn > Pb > Cu, amaranth contributed the highest estimated daily intake for Cd, Cu, Pb and Zn, the health risk index was high for Cd and Pb but low for Cu and Zn, and the hazard index results indicate that vegetables grown on the selected peri-urban farms are not safe for 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.

M. G. Dahiru, Onaiwu Idahosa Enabulele · · Nigeria (Kano)

Microbiological and physicochemical parameters of urban wastewater from the Jakara Canal in Kano were analyzed to assess its potential for irrigation. Mean fecal coliform counts ranged from 64.43 ± 63.20 MPN 100/ml to 216.85 ± 350.16 MPN 100/ml, increasing along the canal. All physicochemical parameters were within FEPA and WHO/FAO acceptable limits, but conductivity needed monitoring to avoid salinity.

Vide Adedayo · Journal of Research in National Development · Nigeria (Lagos)

This study investigated poultry waste management in urban vegetable farms in Metropolitan Lagos from an ecosystem to human health perspective. Using a transdisciplinary approach, community participation, and socio-cultural, physiochemical, microbiological, and clinical information, the research revealed negative impacts and health problems associated with poultry waste management due to poor storage, composting, and packaging techniques. Consequently, adverse effects on users were identified.

Joseph Agossou, Léonard Afouda, Julien Didier Adédémy, Alphonse Noudamadjo, Catherine N’da Tido, Emanliikpon Sylvain Ahohoui, Pierre G. Tovihoudji, Farouk Mazou, Benjami Fayomi, Simon Akpona, Sikiratou Adéothy-Koumakpaï, B Ayivi · Environnement Risques & Sante · Benin (Parakou)

This study analyzed the bacteriological and parasitic load in wastewater and market garden products from five major production sites in Parakou, Benin, where farmers use wastewater for irrigation. High concentrations of fecal coliforms, Escherichia coli, Salmonella enterica, Shigella spp., Entamoeba coli, Giardia intestinalis cysts, and helminth eggs were found in irrigation water, vegetables, and farmers' stools. The use of wastewater resulted in high contamination of vegetables, particularly cabbage, large lettuce, and carrot leaves, by fecal coliforms, Salmonella enterica, and Escherichia coli.

UM Dawaki, A. U. Dikko, SS Noma, U. Aliyu · Nigerian Journal of Basic and Applied Sciences · Nigeria

A study investigated the total, exchangeable, and soluble concentrations of heavy metals (Cu, Cr, Ni, Zn, Pb, Cd) in urban agricultural soils along three rivers (Challawa, Jakara, and Watari) in Kano, Nigeria. Cadmium concentrations at Jakara and Challawa exceeded maximum allowable concentrations in soils. Heavy metal concentrations were found to be significantly higher in areas irrigated with industrial and domestic sewage (Challawa and Jakara) compared to the control site (Watari).

A. N. Mutune, M. A. Makobe, Mary Abukutsa‐Onyango · African Journal of Environmental Science and Technology · Kenya (Nairobi)

This study analyzed heavy metal content in 10 common African leafy vegetables and their rhizosphere soils from 25 sites along Nairobi Rivers, Kenya. While soil metal concentrations were generally within WHO/FAO permissible levels, except for some cadmium instances, all metals except copper in vegetables exceeded recommended limits at a few sites. This indicates potential heavy metal absorption from industrial and domestic effluent.

Suarau Odutola Oshunsanya, Tolafe Olayinka Adeniran · Agricultura tropica et subtropica · Nigeria (Ibadan)

A field experiment in Ibadan investigated the quality of irrigation water used for dry season vegetable cultivation along Ona-stream. Water samples from five isolated ponds and one locally dug well were analyzed for heavy metal status. Results showed high concentrations of Pb, Cr, and Co in soil from five farms (A-E) near the stream, and isolated pond water also contained Cr, Co, and Pb exceeding safe consumption thresholds. All vegetables irrigated with untreated isolated ponds contained Cd, Pb, and Ni concentrations above maximum permissible standards, posing potential risks to human health.

Ande O.T, Adetunji A. M, Akinpelu M. E, Senjobi B.A · Journals & Books Hosting (International Knowledge Sharing Platform) · Nigeria

Ibadan metropolis, Nigeria, home to about 6 million people, has raised growing concern over lowland soils in its periurban area, where much of the industrial waste transported by the River Ona is deposited; these soils are used for dry-season farming and contribute to food security. This study aimed to characterize periurban lowland soils around Ibadan and determine their vulnerability to industrial pollution, using a 50m x 50m grid with surface samples taken at 50m intervals, plus representative profile pits described using the USDA method, and particle-size and chemical analyses (phosphorus, nitrogen, exchangeable cations Ca/Mg/Na/K, manganese, and heavy metals including lead, copper, zinc, chromium, iron, and cadmium). Results showed the floodplain's surface soil was fertile, with high nitrogen (0.35 cmol/kg), phosphorus (51.25 cmol/kg), and potassium (0.61 cmol/kg), and phosphorus levels ranging from very high to toxic, between 28.99 and 87.70 ppm. Average heavy metal concentrations were lead 34.30 mg/kg, zinc 171.20 mg/kg, iron 83.97 mg/kg, copper 19.11 mg/kg, manganese 31.10 mg/kg, chromium 0.69 mg/kg, and cadmium 0.3 mg/kg. Predicted soil-to-plant heavy metal transfer coefficients (Pb 35-343; Cr 0.46-4.6; Zn 171-1712; Cu 19-191; Fe 83-840; Mn 31-281; Cd 0.1-10) indicated crops grown in the area could contain toxic levels of these metals; however, high yields and healthy plant condition observed in the field, together with farmer interviews, suggested that the high phosphorus level (28.99-87 ppm) may have inhibited uptake of some metals such as lead, zinc, and copper.

Mansur Usman Dawaki, Abubakar U. Dikko, S. S. Noma, Umar Aliyu · Food and Energy Security · Nigeria

This study evaluated pollution risks to food security from urban agriculture in Kano, Nigeria, by sampling soil, water, and lettuce from two wastewater-irrigated sites (Challawa, Jakara) and a control site (Watari). Results showed all sites were contaminated with Cu, and the domestic wastewater site was slightly polluted with Pb and excessively polluted with Cd and Cr. Metal levels in irrigation waters exceeded recommended thresholds, and plants at the domestic wastewater site accumulated metal concentrations (Pb=26.21 mg/kg, Cd=1.03 mg/kg, Cr=28.63 mg/kg, Cu=2.66 mg/kg) that exceeded allowable limits in vegetables, indicating a human ingestion risk.

Mekonnen Getahun, Yihenew G. Selassie · Journal of Agricultural Science · Ethiopia

A study investigated the extent of contamination of soil, water, and vegetables from wastewater used for irrigation in urban agriculture in Bahir Dar and Kombolcha, Ethiopia. Soil, water, and vegetable samples were collected and analyzed. While heavy metal concentrations in soil were within permissible levels, wastewater samples showed high nitrate and phosphate levels, and boron concentrations in Borkena River and Lake Tana exceeded permissible limits for irrigation. Wastewater drained to Lake Tana exhibited high turbidity and very high BOD, and lettuce and Swiss chard accumulated higher levels of iron, manganese, and zinc.

Evaristo Mwaba Kapungwe · Open Journal of Metal · Africa

Water, soil, and crop samples were analyzed by atomic absorption spectrometry for lead, copper, cobalt, nickel, and chromium at two peri-urban wastewater-irrigation farming sites in Zambia: New Farm Extension in Mufulira Town, Copperbelt Province, and Chilumba Gardens in Kafue Town, Lusaka Province. Heavy metal levels in wastewater, soil, and food crops exceeded acceptable limits at both sites, confirming contamination and a potential human health risk from consuming the crops grown there.

Léon W. Nitièma, Boubacar Savadogo, Dramane Zongo, Aminata Kaboré, Poda Jean Noël, Alfred S. Traoré, Dayéri Dianou · Journal of Environmental Protection · Africa

This study examined the microbial quality of wastewater used for truck farming in Ouagadougou, Burkina Faso, testing for bacterial and parasitological fecal indicators during the dry-hot season (May) and the wet season (July) of 2012. Wastewater from three water reservoirs and two canals intensively used for truck farming was analyzed, and the same indicators were tracked through waste stabilization ponds at three treatment plants in the city. Concentrations of microbial indicators were significantly higher in the dry-hot season than the wet season across all sampling sites, with levels reaching up to 53,800 CFU/100ml for E. coli, 8,200-108,400 CFU/100ml for fecal coliforms, 650-45,000 CFU/100ml for fecal streptococcus, and 0-2.4 eggs/l for helminths. Through the waste stabilization ponds, significant microbial concentration drops of 82-100%, 78-98%, 60-100%, and 82-88% respectively were recorded between the anaerobic and maturation ponds. The results indicate that improving the refining performance of waste stabilization pond technology could help reduce the health risks associated with wastewater reuse in urban agriculture in developing countries.

G. N. Egwu, John O. Agbenin · Archives of Agronomy and Soil Science · Nigeria

A study in northern Nigeria assessed cadmium, lead, and zinc contamination in soils and leaf vegetables (amaranthus, lettuce) irrigated with untreated wastewater. Total cadmium and zinc concentrations in soils exceeded safe limits, and lead and cadmium in edible portions of amaranthus and lettuce exceeded safe limits for human consumption by 7–17 times. The permissible limit for lead established for agricultural lands may not be suitable to ensure produce safety in urban and peri-urban agriculture in Kano.

Nancy Karanja, Mary Njenga, G.K. Mutua, Carl Johan Lagerkvist, E. Kutto, JJ Okello · Journal of Agriculture Food Systems and Community Development · Kenya (Nairobi)

A study in three peri-urban sites in Nairobi, Kenya, assessed heavy metal, nitrate, and pesticide residue levels in wastewater-irrigated kale. Elevated levels of boron, cobalt, chromium, copper, lead, zinc, and nickel were found in vegetables at two sites, with high soil loadings of nickel, arsenic, lead, chromium, copper, and zinc attributed to chicken manure. Pesticide residues of diazinon, cypermethrin, biternol, and profenofos exceeded permissible limits in kale at one site, suggesting consumers may ingest significant amounts of contaminants.

Sebastian U. Ugbaje, John O. Agbenin · International Journal of Environmental Studies · Nigeria

A pot experiment in Zaria, northern Nigeria, evaluated the chemical forms and phytoavailability of Cr, Ni, and Pb in savannah soil amended with two urban wastes and planted with sorghum. While urban waste application increased total metal concentrations in the soil, only Pb uptake by sorghum increased, with no corresponding increases for Cr and Ni. A single application of urban wastes significantly increased Pb uptake by sorghum, raising concerns about the long-term consequences of such applications in urban and peri-urban agriculture, especially regarding children's exposure to Pb.

Catherine Rwamba Githuku · Abstracts of postgraduate thesis · Kenya (Nairobi)

This study investigated soil and crop pollution levels resulting from untreated wastewater reuse for irrigation in Kibera and Mailisaba wastewater irrigation farms in Nairobi, Kenya. Analysis of irrigation water, soil, and crop samples (maize, kales, black nightshade, arrowroots) revealed that the Electrical Conductivity (EC) of irrigation water at Mailisaba exceeded recommended levels. Farmers reported adverse effects on crops due to wastewater quality, and despite awareness of health risks, many farmers confessed to not using protective clothing.

John Jacob, Samuel E. Kakulu · American Journal of Chemistry · Nigeria

Soil and vegetable samples (spinach, jute mallow, and tomato) were collected from farms and gardens across 20 zones within Kaduna, Nigeria, plus two rural control villages about 30 km from the city, and analyzed for heavy metals by Flame Atomic Absorption Spectrophotometer. Pollution Load Index results showed soils in the city farms were moderately enriched with cadmium and chromium and strongly enriched with lead and nickel from anthropogenic sources. Mean soil concentrations of lead and cadmium exceeded WHO/FAO permissive limits for agricultural soil (nickel and chromium did not), while vegetable metal concentrations exceeded the permissive limits for every metal except nickel — a finding flagged as concerning given the toxicity of lead and cadmium in particular, which have no known biological use.

I. K. Adewumi, Adebanji Samuel Ogbiye, E. O. Longe, David O. Omole · Covenant University Repository (Covenant University) · Nigeria (Ota)

This study assessed the impact of industrial wastewaters discharged into River Atuwara in Ota, Nigeria, on water quality using standard physical and chemical analyses and QUAL2K software. The majority of water quality parameters exceeded maximum permissible concentrations, with BOD at ≥ 31 mg/L, COD at ≥ 181 mg/L, and alkalinity at ≥ 138.4 mg/L. High concentrations of heavy metals, including Cadmium, Pb, Zn, Fe, and Mn, were detected, indicating an environmental hazard for riparian users.