2022 Volume 2
Article Contents
REVIEW   Open Access    

Noxious substance content of vegetables grown in urban and peri-urban areas

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  • Ethiopians are increasingly moving from the countryside to cities, accelerating the process of urban growth. Vegetables are a vital part of overall nutrition because they comprise carbohydrates, proteins, and minerals. Such crops however encompass comparable vital and poisonous materials in different compositions. Among the most critical components of food quality management is the heavy metal pollutants of food products. Cadmium, chromium, copper, mercury, lead, and zinc are the most abundant pollutants. All of these substances are nutritionally important and required for growth. Numerous factors affect heavy metal absorption and biomagnification in vegetables, including weather, degree of contamination in soil conditions, and extent of the crops produce. Heavy metal contamination is generally triggered by pollutants from extraction and a broad range of activities. Protracted intake of dangerous heavy metal content in meals could hinder diverse bioactive substances as well as the metabolic system of the human body. These include persistent metal accumulation in the liver, altering multiple biological pathways that result in cardiac, anxiety, kidney, and skeletal problems. Pollutants pose a huge potential hazard to people of all ages who ingest fruits and vegetables cultivated in polluted soils.
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  • [1]

    Cooper C. 1993. Biological effects of agriculturally derived surface water pollutants on aquatic systems—a review. Journal of environmental quality 22:402−8

    doi: 10.2134/jeq1993.00472425002200030003x

    CrossRef   Google Scholar


    Mee L. 2012. Between the Devil and the Deep Blue Sea: The coastal zone in an Era of globalisation. Estuarine, Coastal and Shelf Science 96:1−8

    doi: 10.1016/j.ecss.2010.02.013

    CrossRef   Google Scholar


    Kanu I, Achi OK. 2011. Industrial Effluents and Their Impact on Water Quality of Receiving Rivers In Nigeria. Journal of Applied Technology in Environmental Sanitation 1:75−86

    Google Scholar


    Schmidt E, Dorosh PA, Kedir Jemal M, Smart J. 2018. Ethiopia's spatial and structural transformation: Public policy and drivers of change. Vol. 119, Ethiopian Development Research Institute


    Butnariu M, Butu A. 2014. Chemical composition of vegetables and their products. In Handbook of Food Chemistry, eds. Cheung PCK, Mehta BM. Heidelberg: Springer, Berlin, Heidelberg. pp. 627−92


    Naik SR, Thakare VN, Joshi FP. 2010. Functional foods and herbs as potential immunoadjuvants and medicines in maintaining healthy immune system: A commentary. Journal of Complementary and Integrative Medicine 7

    doi: 10.2202/1553-3840.1441

    CrossRef   Google Scholar


    Radwan MA, Salama AK. 2006. Market basket survey for some heavy metals in Egyptian fruits and vegetables. Food and chemical toxicology 44(8):1273−78

    doi: 10.1016/j.fct.2006.02.004

    CrossRef   Google Scholar


    Khanna P. 2011. Assessment of heavy metal contamination in different vegetables grown in and around urban areas. Research Journal of Environmental Toxicology 5:162−79

    doi: 10.3923/rjet.2011.162.179

    CrossRef   Google Scholar


    Garbisu C, Alkorta I. 2003. Basic concepts on heavy metal soil bioremediation. European Journal of Mineral Processing and Environmental Protection 3:58−66

    Google Scholar


    He Z, Shentu J, Yang X, Baligar VC, Zhang T, et al. 2015. Heavy metal contamination of soils: sources, indicators and assessment. Journal of Environmental Indicators 9:17−18

    Google Scholar


    Tangahu BV, Sheikh Abdullah SR, Basri H, Idris M, Anuar N, et al. 2011. A review on heavy metals (As, Pb, and Hg) uptake by plants through phytoremediation. International Journal of Chemical Engineering 2011:939161

    doi: 10.1155/2011/939161

    CrossRef   Google Scholar


    Kalaivanan D, Ganeshamurthy AN. 2016. Mechanisms of heavy metal toxicity in plants. In Abiotic stress physiology of horticultural crops, eds. Srinivasa Rao NK, Shivashankara KS, Laxman RH. New Delhi: Springer, New Delhi. p. 85−102


    Rahman Z, Singh VP. 2019. The relative impact of toxic heavy metals (THMs) (arsenic (As), cadmium (Cd), chromium (Cr)(VI), mercury (Hg), and lead (Pb)) on the total environment: an overview. Environmental Monitoring and Assessment 191:419

    doi: 10.1007/s10661-019-7528-7

    CrossRef   Google Scholar


    Tapiero H, Townsend DM, Tew KD. 2003. Trace elements in human physiology and pathology. Copper. Biomedicine & Pharmacotherapy 57:386−98

    doi: 10.1016/S0753-3322(03)00012-X

    CrossRef   Google Scholar


    Jeričević A, I. Ilyin, S. Vidič. 2012. Modelling of heavy metals: study of impacts due to climate change, in National security and human health implications of climate change, eds. Fernando HJS, Klaić Z, McCulley JM. Netherlands: Springer, Dordrecht. pp. 175−89


    Ali H, Khan E, Ilahi I. 2019. Environmental chemistry and ecotoxicology of hazardous heavy metals: environmental persistence, toxicity, and bioaccumulation. Journal of chemistry 2019:6730305

    doi: 10.1155/2019/6730305

    CrossRef   Google Scholar


    Thakur S, Singh L, Wahid ZA, Siddiqui MF, Atnaw SM, et al. 2016. Plant-driven removal of heavy metals from soil: uptake, translocation, tolerance mechanism, challenges, and future perspectives. Environmental Monitoring and Assessment 188:206

    doi: 10.1007/s10661-016-5211-9

    CrossRef   Google Scholar


    Ilker R, Szczesniak AS. 1990. Structural and chemical bases for texture of plant foodstuffs. Journal of Texture Studies 21:1−36

    doi: 10.1111/j.1745-4603.1990.tb00462.x

    CrossRef   Google Scholar


    Gadd GM. 2007. Geomycology: biogeochemical transformations of rocks, minerals, metals and radionuclides by fungi, bioweathering and bioremediation. Mycological Research 111:3−49

    doi: 10.1016/j.mycres.2006.12.001

    CrossRef   Google Scholar


    Sodango TH, Li X, Sha J, Bao Z. 2018. Review of the spatial distribution, source and extent of heavy metal pollution of soil in China: impacts and mitigation approaches. Journal of Health and Pollution 8(7):53−70

    doi: 10.5696/2156-9614-8.17.53

    CrossRef   Google Scholar


    Devi P, Kumar P. 2020. Concept and application of phytoremediation in the fight of heavy metal toxicity. Journal of Pharmaceutical Sciences and Research 12:795−804

    Google Scholar


    Duan Q, Lee J, Liu Y, Chen H, Hu H. 2016. Distribution of heavy metal pollution in surface soil samples in China: a graphical review. Bulletin of Environmental Contamination and Toxicology 97:303−9

    doi: 10.1007/s00128-016-1857-9

    CrossRef   Google Scholar


    Olaniran AO, Balgobind A, Pillay B. 2013. Bioavailability of heavy metals in soil: impact on microbial biodegradation of organic compounds and possible improvement strategies. International Journal of Molecular Sciences 14:10197−228

    doi: 10.3390/ijms140510197

    CrossRef   Google Scholar


    Yeshiwas Y, Tadele E, Tiruneh W. 2019. The dynamics of medicinal plants utilization practice nexus its health and economic role in Ethiopia: A review paper. International Journal of Biodiversity and Conservation 11:31−47

    doi: 10.5897/IJBC2018.1201

    CrossRef   Google Scholar


    Jørgensen N, Laursen J, Viksna A, Pind N, Holm PE. 2005. Multi-elemental EDXRF mapping of polluted soil from former horticultural land. Environment International 31:43−52

    doi: 10.1016/j.envint.2004.06.007

    CrossRef   Google Scholar


    Sharma RK, Agrawal M, Marshall F. 2006. Heavy metal contamination in vegetables grown in wastewater irrigated areas of Varanasi, India. Bulletin of Environmental Contamination and Toxicology 77:312−18

    doi: 10.1007/s00128-006-1065-0

    CrossRef   Google Scholar


    Förstner U. 1981. Metal Pollution Assessment from Sediment Analysis. In Metal pollution in the aquatic environment. Heidelberg: Springer, Berlin, Heidelberg. pp. 110−96


    Wuana RA, Okieimen FE. 2011. Heavy metals in contaminated soils: a review of sources, chemistry, risks and best available strategies for remediation. International Scholarly Research Notices 2011:402647

    doi: 10.5402/2011/402647

    CrossRef   Google Scholar


    Abioye OP. 2011. Biological remediation of hydrocarbon and heavy metals contaminated soil. In Soil Contamination, ed. Pascucci S. London: IntechOpen. pp. 127−42


    Donkor A, Fordjour LA, Tawiah R, Asomaning W, Dubey B, et al. 2017. Evaluation of trace metals in vegetables sampled from farm and market sites of Accra Metropolis, Ghana. International Journal of Environmental Studies 74:315−24

    doi: 10.1080/00207233.2016.1261599

    CrossRef   Google Scholar


    Raschid-Sally L, Jayakody P. 2009. Drivers and characteristics of wastewater agriculture in developing countries: Results from a global assessment. Research Report. Rep. 127. International Water Management Institute, Colombo, Sri Lanka.


    Kabata-Pendias A. 2004. Soil-plant transfer of trace elements — an environmental issue. Geoderma 122:143−49

    doi: 10.1016/j.geoderma.2004.01.004

    CrossRef   Google Scholar


    Kader AA, Rolle RS. 2004. The role of post-harvest management in assuring the quality and safety of horticultural produce. Vol. 152. Rome: Food and Agriculture Organization of the United Nations, ©2004.


    Gupta N, Khan DK, Santra S. 2012. Heavy metal accumulation in vegetables grown in a long-term wastewater-irrigated agricultural land of tropical India. Environmental Monitoring and Assessment 184:6673−82

    doi: 10.1007/s10661-011-2450-7

    CrossRef   Google Scholar


    Rattan RK, Datta SP, Chhonkar PK, Suribabu K, Singh AK. 2005. Long-term impact of irrigation with sewage effluents on heavy metal content in soils, crops and groundwater — a case study. Agriculture, Ecosystems & Environment 109:310−22

    doi: 10.1016/j.agee.2005.02.025

    CrossRef   Google Scholar


    Clarkson D.T. 1984. Calcium transport between tissues and its distribution in the plant. Plant, Cell & Environment 7:449−56

    doi: 10.1111/j.1365-3040.1984.tb01435.x

    CrossRef   Google Scholar


    Gonçalves AC Jr, Schwantes D, Braga de Sousa RF, Benetoli da Silva TR, Guimarães VF, et al. 2020. Phytoremediation capacity, growth and physiological responses of Crambe abyssinica Hochst on soil contaminated with Cd and Pb. Journal of Environmental Management 262:110342

    doi: 10.1016/j.jenvman.2020.110342

    CrossRef   Google Scholar


    Latif A, Bilal M, Asghar W, Azeem M, Ahmad MI, et al. 2018. Heavy metal accumulation in vegetables and assessment of their potential health risk. Journal of Environmental Analytical Chemistry 5:2380−91

    doi: 10.4172/2380-2391.1000234

    CrossRef   Google Scholar


    Hall JL. 2002. Cellular mechanisms for heavy metal detoxification and tolerance. Journal of experimental botany 53:1−11

    Google Scholar


    Itanna F. 2002. Metals in leafy vegetables grown in Addis Ababa and toxicological implications. Ethiopian Journal of Health Development 16:295−302

    doi: 10.4314/ejhd.v16i3.9797

    CrossRef   Google Scholar


    Woldetsadik D, Drechsel P, Keraita B, Itanna F, Gebrekidan H. 2017. Heavy metal accumulation and health risk assessment in wastewater-irrigated urban vegetable farming sites of Addis Ababa, Ethiopia. International Journal of Food Contamination 4:1−13

    doi: 10.1186/s40550-017-0053-y

    CrossRef   Google Scholar


    Oyinloye I. 2016. Bioremediation of Heavy Metals Contaminated Soil from A Steel Rolling Company in Ibadan. Doctoral dissertation. University of Ibadan Nigeria. 188 pp.


    Sharma RK, Agrawal M, Marshall FM. 2008. Heavy metal (Cu, Zn, Cd and Pb) contamination of vegetables in urban India: A case study in Varanasi. Environmental Pollution 154:254−63

    doi: 10.1016/j.envpol.2007.10.010

    CrossRef   Google Scholar


    Bhatia A, Singh S, Kumar A. 2015. Heavy metal contamination of soil, irrigation water and vegetables in peri-urban agricultural areas and markets of Delhi. Water Environment Research 87:2027−34

    doi: 10.2175/106143015X14362865226833

    CrossRef   Google Scholar


    Kamiab F, Zamanibahramabadi E. 2016. The effect of foliar application of nano-chelate super plus ZFM on fruit set and some quantitative and qualitative traits of almond commercial cultivars. Journal of Nuts 7:9−20

    doi: 10.22034/JON.2016.522950

    CrossRef   Google Scholar


    Chen Y, Wang J, Shi G, Sun X, Chen Z, et al. 2011. Human health risk assessment of lead pollution in atmospheric deposition in Baoshan District, Shanghai. Environmental Geochemistry and Health 33:515−23

    doi: 10.1007/s10653-010-9368-9

    CrossRef   Google Scholar


    Al Jassir MS, Shaker A, Khaliq MA. 2005. Deposition of heavy metals on green leafy vegerables sold on roadsides of Riyadh City, Saudi Arabia. Bulletin of Environmental Contamination and Toxicology 75:1020−27

    doi: 10.1007/s00128-005-0851-4

    CrossRef   Google Scholar


    Sharma RK, Agrawal M, Marshall FM. 2009. Heavy metals in vegetables collected from production and market sites of a tropical urban area of India. Food and Chemical Toxicology 47:583−91

    doi: 10.1016/j.fct.2008.12.016

    CrossRef   Google Scholar


    Girma G. 2015. Microbial bioremediation of some heavy metals in soils: an updated review. Egyptian Academic Journal of Biological Sciences, G. Microbiology 7:29−45

    doi: 10.21608/eajbsg.2015.16483

    CrossRef   Google Scholar


    Mishra AK, Singh J, Mishra PP. 2020. Toxic metals in crops: a burgeoning problem. In Sustainable Solutions for Elemental Deficiency and Excess in Crop Plants, eds. Mishra K, Tandon PK, Srivastava S. Singapore: Springer. pp. 273−301


    Du Jardin P. 2015. Plant biostimulants: definition, concept, main categories and regulation. Scientia Horticulturae 196:3−14

    doi: 10.1016/j.scienta.2015.09.021

    CrossRef   Google Scholar


    Aguilera JM. 2012. Edible structures: The basic science of what we eat. Boca Raton: CRC Press. 462 pp


    Chutia P, Kato S, Kojima T, Satokawa S. 2009. Arsenic adsorption from aqueous solution on synthetic zeolites. Journal of Hazardous Materials 162:440−47

    doi: 10.1016/j.jhazmat.2008.05.061

    CrossRef   Google Scholar


    Andrianisa HA, Ito A, Sasaki A, Aizawa J, Umita T. 2008. Biotransformation of arsenic species by activated sludge and removal of bio-oxidised arsenate from wastewater by coagulation with ferric chloride. Water Research 42:4809−17

    doi: 10.1016/j.watres.2008.08.027

    CrossRef   Google Scholar


    Raikwar MK, Kumar P, Singh M, Singh A. 2008. Toxic effect of heavy metals in livestock health. Veterinary World 1:28−30

    doi: 10.5455/vetworld.2008.28-30

    CrossRef   Google Scholar


    Kolthoff I, J. Coetzee. 1957. Polarography in Acetonitrile. 1 I. Metal Ions which Have comparable polarographic properties in acetonitrile and in water. Journal of the American Chemical Society 79(4):870−874

    doi: 10.1021/ja01561a023

    CrossRef   Google Scholar


    Duce RA, Liss PS, Merrill JT, Atlas EL, Buat-Menard P, et al. 1991. The atmospheric input of trace species to the world ocean. Global Biogeochemical Cycles 5:193−259

    doi: 10.1029/91GB01778

    CrossRef   Google Scholar


    Mahurpawar M. 2015. Effects of heavy metals on human health. International Journal of Research-Granthaalayah 3:1−7

    doi: 10.29121/granthaalayah.v3.i9se.2015.3282

    CrossRef   Google Scholar


    Pehlivan E, Özkan AM, Dinç S, Parlayici Ş. 2009. Adsorption of Cu2+ and Pb2+ ion on dolomite powder. Journal of Hazardous Materials 167:1044−49

    doi: 10.1016/j.jhazmat.2009.01.096

    CrossRef   Google Scholar


    Baruah S, Dutta J. 2009. Nanotechnology applications in pollution sensing and degradation in agriculture: a review. Environmental Chemistry Letters 7:191−204

    doi: 10.1007/s10311-009-0228-8

    CrossRef   Google Scholar


    Knap A, Dewailly É, Furgal C, Galvin J, Baden D, et al. 2002. Indicators of ocean health and human health: developing a research and monitoring framework. Environmental Health Perspectives 110:839−45

    doi: 10.1289/ehp.02110839

    CrossRef   Google Scholar


    Yi Y, Yang Z, Zhang Z. 2011. Ecological risk assessment of heavy metals in sediment and human health risk assessment of heavy metals in fishes in the middle and lower reaches of the Yangtze River basin. Environmental Pollution 159:2575−85

    doi: 10.1016/j.envpol.2011.06.011

    CrossRef   Google Scholar


    Robinson JB, Tuovinen OH. 1984. Mechanisms of microbial resistance and detoxification of mercury and organomercury compounds: physiological, biochemical, and genetic analyses. Microbiological reviews 48:95−124

    doi: 10.1128/mr.48.2.95-124.1984

    CrossRef   Google Scholar


    Patra M, Bhowmik N, Bandopadhyay B, Sharma A. 2004. Comparison of mercury, lead and arsenic with respect to genotoxic effects on plant systems and the development of genetic tolerance. Environmental and Experimental Botany 52:199−223

    doi: 10.1016/j.envexpbot.2004.02.009

    CrossRef   Google Scholar


    Akinsola R, Mohammed M, Malami D. 2014. Study of Atmospheric Pollution Levels by Trace Lead (element) Analysis of Tree Barks and Soils. International Journal of Modern Analytical and Separation Sciences 3:40−50

    doi: 10.13140/RG.2.2.35614.05444

    CrossRef   Google Scholar


    Cabaniss AD ed. 2008. Handbook on household hazardous waste: Rowman & Littlefield. Lanham, Maryland, US: Government Institutes, The Scarecrow Press, Inc.


    Podust VN, Balan S, Sim BC, Coyle MP, Ernst U, et al. 2016. Extension of in vivo half-life of biologically active molecules by XTEN protein polymers. Journal of Controlled Release 240:52−66

    doi: 10.1016/j.jconrel.2015.10.038

    CrossRef   Google Scholar


    Volesky B. 1990. Removal and recovery of heavy metals by biosorption. In Biosorption of heavy metals. Boca Raton, FL: CRC Press. pp. 7−43


    Aboh NA. 2018. Pattern of Thyroid Autoantibodies, Essential and Toxic Trace Elements in Various Thyroid Disorders in Nigeria. Doctoral dissertation. University of Ibadan, Nigeria.


    Jaishankar M, Tseten T, Anbalagan N, Mathew BB, Beeregowda KN. 2014. Toxicity, mechanism and health effects of some heavy metals. Interdisciplinary Toxicology 7:60−72

    doi: 10.2478/intox-2014-0009

    CrossRef   Google Scholar


    Benedetti JL, Turcotte F, Lefebvre M, Therrien F, Weber JP. 1992. Blood and urinary cadmium levels in Inuit living in Kuujjuaq, Canada. Science of the Total Environment 127:167−72

    doi: 10.1016/0048-9697(92)90475-8

    CrossRef   Google Scholar


    Lorena J, Barlič-Maganja D, Lojkić M, Madić J, Grom J, et al. 2001. Classical swine fever virus (C strain) distribution in organ samples of inoculated piglets. Veterinary Microbiology 81:1−8

    doi: 10.1016/S0378-1135(01)00321-2

    CrossRef   Google Scholar


    Nasreddine L, Parent-Massin D. 2002. Food contamination by metals and pesticides in the European Union. Should we worry? Toxicology letters 127:29−41

    doi: 10.1016/S0378-4274(01)00480-5

    CrossRef   Google Scholar


    Onakpa MM, Njan AA, Kalu OC. 2018. A review of heavy metal contamination of food crops in Nigeria. Annals of Global Health 84:488−94

    doi: 10.29024/aogh.2314

    CrossRef   Google Scholar


    Wondimu A. 2015. Addis Ababa Institute of Technology (AAiT) School of Chemical and Bio-Engineering. Doctoral dissertation. Addis Ababa University Addis Ababa. Process Parameters Optimization and Development of Extruded Teff Based Snacks. file:///C:/Users/user/Downloads/AsnakechWondimu.pdf.


    Joint F.A.O, World Health Organization. 1997. Food consumption and exposure assessment of chemicals. FAO/WHO Consulation on Food Consumption and Exposure Assessment of Chemicals, Geneva, 10−14 February 1997


    Qadir M, Sharma BR, Bruggeman A, Choukr-Allah R, Karajeh F. 2007. Non-conventional water resources and opportunities for water augmentation to achieve food security in water scarce countries. Agricultural water management 87:2−22

    doi: 10.1016/j.agwat.2006.03.018

    CrossRef   Google Scholar


    Agrawal J, Sherameti I, Varma A. 2011. Detoxification of heavy metals: State of art. In Detoxification of Heavy Metals, Soil Biology, eds. Sherameti I, Varma A. vol 30. Heidelberg: Springer, Berlin, Heidelberg. pp. 1−34


    Loganathan P, Vigneswaran S, Kandasamy J, Naidu R. 2012. Cadmium sorption and desorption in soils: a review. Critical Reviews in Environmental Science and Technology 42:489−533

    doi: 10.1080/10643389.2010.520234

    CrossRef   Google Scholar


    Gerber GB, Léonard A, Hantson P. 2002. Carcinogenicity, mutagenicity and teratogenicity of manganese compounds. Critical reviews in Oncology/Hematology 42:25−34

    doi: 10.1016/S1040-8428(01)00178-0

    CrossRef   Google Scholar


    Ross EJ, Graham DL, Money KM, Stanwood GD. 2015. Developmental consequences of fetal exposure to drugs: what we know and what we still must learn. Neuropsychopharmacology 40:61−87

    doi: 10.1038/npp.2014.147

    CrossRef   Google Scholar


    Zhang J, Mauzerall DL, Zhu T, Liang S, Ezzati M, et al. 2010. Environmental health in China: progress towards clean air and safe water. The Lancet 375:1110−19

    doi: 10.1016/S0140-6736(10)60062-1

    CrossRef   Google Scholar


    Nazif W, Perveen S, Shah SA. 2006. Evaluation of irrigation water for heavy metals of Akbarpura area. American Journal of Agricultural and Biological science 1:51−54

    Google Scholar


    Pais I, Jones JB Jr. 1997. The Handbook of Trace Elements. Boca Raton: St. Lucie Press, 223 pp


    Izah SC, Inyang IR, Angaye TCN, Okowa IP. 2016. A review of heavy metal concentration and potential health implications of beverages consumed in Nigeria. Toxics 5:1

    doi: 10.3390/toxics5010001

    CrossRef   Google Scholar


    Li X, Liu L, Wang Y, Luo G, Chen X, et al. 2013. Heavy metal contamination of urban soil in an old industrial city (Shenyang) in Northeast China. Geoderma 192:50−58

    doi: 10.1016/j.geoderma.2012.08.011

    CrossRef   Google Scholar


    Hamba Y, Tamiru M. 2016. Mycoremediation of heavy metals and hydrocarbons contaminated environment. Asian Journal of Natural & Applied Sciences 5:48−58

    Google Scholar


    Roba C, Roşu C, Piştea I, Ozunu A, Baciu C. 2016. Heavy metal content in vegetables and fruits cultivated in Baia Mare mining area (Romania) and health risk assessment. Environmental Science and Pollution Research 23:6062−73

    doi: 10.1007/s11356-015-4799-6

    CrossRef   Google Scholar


    Bagdatlioglu N, Nergiz C, Ergonul PG. 2010. Heavy metal levels in leafy vegetables and some selected fruits. Journal für Verbraucherschutz und Lebensmittelsicherheit 5:421−28

    doi: 10.1007/s00003-010-0594-y

    CrossRef   Google Scholar


    Salt DE, Blaylock M, Kumar NP, Dushenkov V, Ensley BD, et al. 1995. Phytoremediation: a novel strategy for the removal of toxic metals from the environment using plants. Bio/Technology 13:468−74

    doi: 10.1038/nbt0595-468

    CrossRef   Google Scholar


    Srinivas N, Krause A, Kakade SM, Seeger M. 2009. Gaussian process optimization in the bandit setting: No regret and experimental design. arXiv Preprint arXiv:0912.3995

    Google Scholar


    Farooq S, Hashmi I, Qazi IA, Qaiser S, Rasheed S. 2008. Monitoring of Coliforms and chlorine residual in water distribution network of Rawalpindi, Pakistan. Environmental Monitoring and Assessment 140:339−47

    doi: 10.1007/s10661-007-9872-2

    CrossRef   Google Scholar


    Farooq M, Anwar F, Rashid U. 2008. Appraisal of heavy metal contents in different vegetables grown in the vicinity of an industrial area. Pakistan Journal of Botany 40:2099−106

    Google Scholar


    Chove BE, Ballegu WR, Chove LM. 2006. Copper and Lead levels in two popular leafy vegetables grown around Morogoro Municipality, Tanzania. Tanzania Journal of Health Research 8:37−40

    doi: 10.4314/thrb.v8i1.14269

    CrossRef   Google Scholar


    Onianwa PC, Adeyemo AO, Idowu OE, Ogabiela EE. 2001. Copper and zinc contents of Nigerian foods and estimates of the adult dietary intakes. Food Chemistry 72:89−95

    doi: 10.1016/S0308-8146(00)00214-4

    CrossRef   Google Scholar


    Sharma VK, Yngard RA, Lin Y. 2009. Silver nanoparticles: green synthesis and their antimicrobial activities. Advances in Colloid and Interface Science 145:83−96

    doi: 10.1016/j.cis.2008.09.002

    CrossRef   Google Scholar


    Aschale M, Sileshi Y, Kelly-Quinn M, Hailu D. 2015. Assessment of potentially toxic elements in vegetables grown along Akaki River in Addis Ababa and potential health implications. Food Science and Quality Management 40:42−52

    Google Scholar


    Hailu A. 2007. Metal concentration in vegetables grown in Northern Addis Ababa and part of rift valley (Ziway), Ethiopia. Doctoral dissertation. Addis Ababa University, Ethiopia.


    Gindaba J, Olsson M, Itanna F. 2004. Nutrient composition and short-term release from Croton macrostachyus Del. and Millettia ferruginea (Hochst.) Baker leaves. Biology and Fertility of Soils 40:393−397

    doi: 10.1007/s00374-004-0767-x

    CrossRef   Google Scholar


    Alemayehu T, Ayenew T, Kebede S. 2006. Hydrogeochemical and lake level changes in the Ethiopian Rift. Journal of Hydrology 316:290−300

    doi: 10.1016/j.jhydrol.2005.04.024

    CrossRef   Google Scholar


    Tegegn F. 2012. Physico-chemical pollution pattern along Akaki River basin, Addis Ababa, Ethiopia.


    Benti G. 2014. Assessment of heavy metals in vegetables irrigated with Awashi River in selected farms around Adama town, Ethiopia. African journal of Environmental Science and Technology 8:428−34

    doi: 10.5897/AJEST2014.1732

    CrossRef   Google Scholar


    Keefer RF, Singh RN, Horvath DJ. 1986. Chemical composition of vegetables grown on an agricultural soil amended with sewage sludges. Journal of Environmental Quality 15:146−52

    doi: 10.2134/jeq1986.00472425001500020012x

    CrossRef   Google Scholar


    Asfaw A, Sime M, Itanna F. 2013. Determining the extent of contamination of vegetables affected by tannery effluent in Ejersa area of East Shoa, Ethiopia. International Journal of Scientific and Research Publications 3:1−7

    Google Scholar


    Bahiru DB. 2021. Assessment of some heavy metals contamination in some vegetables (tomato, cabbage, lettuce and onion) in Ethiopia: A review. American Journal of Environmental Protection 10:53−58

    doi: 10.11648/j.ajep.20211002.12

    CrossRef   Google Scholar


    Harrison RM, Chirgawi MB. 1989. The assessment of air and soil as contributors of some trace metals to vegetable plants I. Use of a filtered air growth cabinet. Science of the Total Environment 83:13−34

    doi: 10.1016/0048-9697(89)90003-X

    CrossRef   Google Scholar


    Goyer RA. 1996. Results of lead research: prenatal exposure and neurological consequences. Environmental Health Perspectives 104:1050−54

    doi: 10.1289/ehp.961041050

    CrossRef   Google Scholar


    Tamiru SM. 2018. Assessment of the impact of anthropogenic activities on water quality, biodiversity and livelihood in Lake Tana, Northwestern Ethiopia. Doctoral dissertation. University of South Africa.


    Weldegebriel Y, Chandravanshi BS, Wondimu T. 2012. Concentration levels of metals in vegetables grown in soils irrigated with river water in Addis Ababa, Ethiopia. Ecotoxicology and Environmental Safety 77:57−63

    doi: 10.1016/j.ecoenv.2011.10.011

    CrossRef   Google Scholar


    Prabu PC. 2009. Impact of heavy metal contamination of Akaki River of Ethiopia on soil and metal toxicity on cultivated vegetable crops. Electronic Journal of Environmental, Agricultural and Food Chemistry 8:819−27

    Google Scholar


    Amin N, Hussain A, Alamzeb S, Begum S. 2013. Accumulation of heavy metals in edible parts of vegetables irrigated with waste water and their daily intake to adults and children, District Mardan, Pakistan. Food Chemistry 136:1515−23

    doi: 10.1016/j.foodchem.2012.09.058

    CrossRef   Google Scholar


    Arora M, Kiran B, Rani S, Rani A, Kaur B, et al. 2008. Heavy metal accumulation in vegetables irrigated with water from different sources. Food Chemistry 111:811−15

    doi: 10.1016/j.foodchem.2008.04.049

    CrossRef   Google Scholar


    Sardar K, Ali S, Hameed S, Afzal S, Fatima S, et al. 2013. Heavy metals contamination and what are the impacts on living organisms. Greener Journal of Environmental Management and Public Safety 2:172−79

    doi: 10.15580/GJEMPS.2013.4.060413652

    CrossRef   Google Scholar


    You R, Margenat A, Lanzas CS, Cañameras N, Carazo N, et al. 2020. Dose effect of Zn and Cu in sludge-amended soils on vegetable uptake of trace elements, antibiotics, and antibiotic resistance genes: Human health implications. Environmental Research 191:109879

    doi: 10.1016/j.envres.2020.109879

    CrossRef   Google Scholar


    Demirezen D, Aksoy A. 2006. Heavy metal levels in vegetables in Turkey are within safe limits for Cu, Zn, Ni and exceeded for Cd and Pb. Journal of Food Quality 29:252−65

    doi: 10.1111/j.1745-4557.2006.00072.x

    CrossRef   Google Scholar


    Bradshaw A. 1997. Restoration of mined lands—using natural processes. Ecological Engineering 8:255−269

    doi: 10.1016/S0925-8574(97)00022-0

    CrossRef   Google Scholar


    Dzimado E. 2015. Assessment of contamination levels and estimation of dietary intake of heavy metals from selected imported fruits and vegetables in Ghana. Mississippi State University, Mississippi


    Alam MGM, Snow ET, Tanaka A. 2003. Arsenic and heavy metal contamination of vegetables grown in Samta village, Bangladesh. Science of The Total Environment 308:83−96

    doi: 10.1016/S0048-9697(02)00651-4

    CrossRef   Google Scholar


    Nabulo G, Oryem-Origa H, Diamond M. 2006. Assessment of lead, cadmium, and zinc contamination of roadside soils, surface films, and vegetables in Kampala City, Uganda. Environmental Research 101:42−52

    doi: 10.1016/j.envres.2005.12.016

    CrossRef   Google Scholar


    Gavrilescu M. 2004. Removal of heavy metals from the environment by biosorption. Engineering in Life Sciences 4:219−32

    doi: 10.1002/elsc.200420026

    CrossRef   Google Scholar


    Kim B.J, Jun H, Lee J, Linton K, Kim M, et al. 2017. Subjective well-being in older Chinese and Korean immigrants in the United States: effects of self-rated health and employment status. Social Work in Public Health 32:510−20

    doi: 10.1080/19371918.2017.1373719

    CrossRef   Google Scholar


    Sharma S, Singh B, Manchanda VK. 2015. Phytoremediation: role of terrestrial plants and aquatic macrophytes in the remediation of radionuclides and heavy metal contaminated soil and water. Environmental Science and Pollution Research 22:946−62

    doi: 10.1007/s11356-014-3635-8

    CrossRef   Google Scholar


    Kensa VM. 2011. Bioremediation - an overview. Journal of Industrial Pollution Control 27:161−68

    Google Scholar


    Kumar V, Shahi SK, Singh S. 2018. Bioremediation: an eco-sustainable approach for restoration of contaminated sites. In Microbial bioprospecting for sustainable development, eds. Singh J, Sharma D, Kumar G, Sharma N. Singapore: Springer. pp. 115−36


    Azubuike CC, Chikere CB, Okpokwasili GC. 2016. Bioremediation techniques–classification based on site of application: principles, advantages, limitations and prospects. World Journal of Microbiology and Biotechnology 32:180

    doi: 10.1007/s11274-016-2137-x

    CrossRef   Google Scholar


    Sangvanich T, Morry J, Fox C, Ngamcherdtrakul W, Goodyear S, et al. 2014. Novel oral detoxification of mercury, cadmium, and lead with thiol-modified nanoporous silica. ACS Applied Materials & Interfaces 6:5483−93

    doi: 10.1021/am5007707

    CrossRef   Google Scholar


    Rai PK. 2009. Heavy metal phytoremediation from aquatic ecosystems with special reference to macrophytes. Critical Reviews in Environmental Science and Technology 39:697−753

    doi: 10.1080/10643380801910058

    CrossRef   Google Scholar


    Cunningham SD, Ow DW. 1996. Promises and prospects of phytoremediation. Plant Physiology 110:715−19

    doi: 10.1104/pp.110.3.715

    CrossRef   Google Scholar


    Wang Z, Ma L, Jia Z, Qin C. 2011. Current status of poplar for phytoremediation. 2011 International Conference on Computer Distributed Control and Intelligent Environmental Monitoring, Changsha, China, 19−20 Feb. 2011, pp. 2031−34. China: IEEE


    Sharma P, Pandey S. 2014. Status of phytoremediation in world scenario. International Journal of Environmental Bioremediation & Biodegradation 2:178−91

    Google Scholar


    Habib MK. 2007. Controlled biological and biomimetic systems for landmine detection. Biosensors and Bioelectronics 23:1−18

    doi: 10.1016/j.bios.2007.05.005

    CrossRef   Google Scholar


    Xie Q, Yan X, Liao X, Li X. 2009. The arsenic hyperaccumulator fern Pteris vittata L. Environmental Science & Technology 43:8488−95

    doi: 10.1021/es9014647

    CrossRef   Google Scholar


    Webb SM, Gaillard JF, Ma LQ, Tu C. 2003. XAS speciation of arsenic in a hyper-accumulating fern. Environmental Science & Technology 37:754−60

    doi: 10.1021/es0258475

    CrossRef   Google Scholar


    Greger M, Landberg T. 1999. Use of willow in phytoextraction. International Journal of Phytoremediatio 1:115−123

    doi: 10.1080/15226519908500010

    CrossRef   Google Scholar


    Brown KS. 1995. The green clean: The emerging field of phytoremediation takes root. BioScience 45:579−82

    doi: 10.2307/1312760

    CrossRef   Google Scholar


    Kaplan D. 2013. Absorption and adsorption of heavy metals by microalgae. In Handbook of microalgal culture: applied phycology and biotechnology, eds. Richmond A, Hu Q. Second Edition. UK: John Wiley & Sons. pp. 602−11


    Satar R. 2010. Applications of soluble and immobilized plant peroxidases in the decolorization and remediation of textile dyes from polluted water.


    Muthusaravanan S, Sivarajasekar N, Vivek JS, Paramasivan T, Naushad M, et al. 2018. Phytoremediation of heavy metals: mechanisms, methods and enhancements. Environmental Chemistry Letters 16:1339−59

    doi: 10.1007/s10311-018-0762-3

    CrossRef   Google Scholar


    Haq S, Bhatti AA, Dar ZA, Bhat SA. 2020. Phytoremediation of heavy metals: an eco-friendly and sustainable approach. In Bioremediation and Biotechnology, eds. Hakeem KR, Bhat RA, Qadri H. Switzerland: Springer, Cham. pp. 215−31


    Gavrilescu M. 2005. Fate of pesticides in the environment and its bioremediation. Engineering in Life Sciences 5:497−526

    doi: 10.1002/elsc.200520098

    CrossRef   Google Scholar


    Cunningham SD, Berti WR. 1993. Remediation of contaminated soils with green plants: an overview. In Vitro Cellular & Developmental Biology-Plant 29:207−12

    doi: 10.1007/BF02632036

    CrossRef   Google Scholar


    Kumawat K, Keshani, Nagpal S, Sharma P. 2021. Present scenario of bio-fertilizer production and marketing around the globe. In Biofertilizers, eds. Rakshit A, Meena VS, Parihar M, Singh HB, Singh AK. UK: Woodhead Publishing, Elsevier, pp. 389−413


    Burylo M, Dutoit T, Rey F. 2014. Species traits as practical tools for ecological restoration of marly eroded lands. Restoration Ecology 22:633−40

    doi: 10.1111/rec.12113

    CrossRef   Google Scholar


    Bhargava A, Carmona FF, Bhargava M, Srivastava S. 2012. Approaches for enhanced phytoextraction of heavy metals. Journal of Environmental Management 105:103−20

    doi: 10.1016/j.jenvman.2012.04.002

    CrossRef   Google Scholar


    Fageria NK, Baligar VC, Li YC. 2008. The role of nutrient efficient plants in improving crop yields in the twenty first century. Journal of Plant Nutrition 31:1121−57

    doi: 10.1080/01904160802116068

    CrossRef   Google Scholar


    McBride MB, Simon T, Tam G, Wharton S. 2013. Lead and arsenic uptake by leafy vegetables grown on contaminated soils: effects of mineral and organic amendments. Water, Air, & Soil Pollution 224:1378

    doi: 10.1007/s11270-012-1378-z

    CrossRef   Google Scholar


    Wu F, Bao W, Li F, Wu N. 2008. Effects of drought stress and N supply on the growth, biomass partitioning and water-use efficiency of Sophora davidii seedlings. Environmental and experimental botany 63:248−55

    doi: 10.1016/j.envexpbot.2007.11.002

    CrossRef   Google Scholar


    Ghosh M, Singh S. 2005. A review on phytoremediation of heavy metals and utilization of its byproducts. Applied Ecology and Environmental Research 3:1−18

    Google Scholar


    Saxena G, Purchase D, Mulla SI, Saratale GD, Bharagava RN. 2019. Phytoremediation of heavy metal-contaminated sites: eco-environmental concerns, field studies, sustainability issues, and future prospects. In Reviews of Environmental Contamination and Toxicology, ed. de Voogt P. Vol. 249:XIV, 201. Switzerland: Springer, Cham. pp. 71−131


    Rashid MI, Mujawar LH, Shahzad T, Almeelbi T, Ismail IM, et al. 2016. Bacteria and fungi can contribute to nutrients bioavailability and aggregate formation in degraded soils. Microbiological Research 183:26−41

    doi: 10.1016/j.micres.2015.11.007

    CrossRef   Google Scholar


    Oeffinger KC, Hudson MM. 2004. Long-term complications following childhood and adolescent cancer: foundations for providing risk-based health care for survivors. CA: A Cancer Journal for Clinicians 54:208−36

    doi: 10.3322/canjclin.54.4.208

    CrossRef   Google Scholar


    Gall JE, Boyd RS, Rajakaruna N. 2015. Transfer of heavy metals through terrestrial food webs: a review. Environmental Monitoring and Assessment 187:201

    doi: 10.1007/s10661-015-4436-3

    CrossRef   Google Scholar

  • Cite this article

    Gelaye Y. 2022. Noxious substance content of vegetables grown in urban and peri-urban areas. Food Materials Research 2:5 doi: 10.48130/FMR-2022-0005
    Gelaye Y. 2022. Noxious substance content of vegetables grown in urban and peri-urban areas. Food Materials Research 2:5 doi: 10.48130/FMR-2022-0005


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Noxious substance content of vegetables grown in urban and peri-urban areas

Food Materials Research  2 Article number: 5  (2022)  |  Cite this article

Abstract: Ethiopians are increasingly moving from the countryside to cities, accelerating the process of urban growth. Vegetables are a vital part of overall nutrition because they comprise carbohydrates, proteins, and minerals. Such crops however encompass comparable vital and poisonous materials in different compositions. Among the most critical components of food quality management is the heavy metal pollutants of food products. Cadmium, chromium, copper, mercury, lead, and zinc are the most abundant pollutants. All of these substances are nutritionally important and required for growth. Numerous factors affect heavy metal absorption and biomagnification in vegetables, including weather, degree of contamination in soil conditions, and extent of the crops produce. Heavy metal contamination is generally triggered by pollutants from extraction and a broad range of activities. Protracted intake of dangerous heavy metal content in meals could hinder diverse bioactive substances as well as the metabolic system of the human body. These include persistent metal accumulation in the liver, altering multiple biological pathways that result in cardiac, anxiety, kidney, and skeletal problems. Pollutants pose a huge potential hazard to people of all ages who ingest fruits and vegetables cultivated in polluted soils.

    • Increase in population, agricultural activity, urbanization, and industrial expansion have all harmed the environment, and pollution has reached worrisome levels. The environmental impacts of human activity include habitat destruction, and water pollution[1].

      Until recent times, environmental degradation and deterioration of water quality were not serious problems as human populations were small and lived in scattered communities[2]. The quantity and complexity of waste were much lower than the environment's assimilative capacity, and thus waste dumped into rivers were subject to diffusion and natural self-purification[3].

      Ethiopia's population is increasingly moving from rural regions to large cities, resulting in rapid urbanization. The country has seen major demographic changes in the last decade, including increased rural-to-urban migration and a 'youth prominence'. Approximately 48% of the current population is under 15 years old[4].

      Vegetables are an important part of the human diet as they provide essential carbohydrates, vitamins, minerals, and fibers[5]. They also serve as acid neutralizers during digestion. Vegetables have a texture and hardness due to the presence of cellulose, hemicellulose, and pectin components. These are key defense foods that are beneficial for maintaining health as well as the prevention and treatment of a variety of illnesses[6]. On the other hand, these crops contain harmful heavy metals in varying amounts[7].

      Pollution and contamination of the human food chain has become unavoidable as human activity grows, especially with the use of contemporary technology[8]. In high concentrations they cause severe damage to the soil and plants. Therefore, they are assumed to be toxic.

      Due to growing knowledge of the risk that toxic metals represent to food chain contamination, international and national food quality laws have decreased the maximum permitted amounts of toxic metals in food items[8].

      Any element with metallic characteristics, and an atomic number of more than 20 is referred to as heavy metal[9]. Cadmium, Cr, Cu, Hg, Pb, and Zn are the most common heavy metal pollutants[10]. Metals are found naturally in soil. Some of these metals, Zn, Cu, Mn, Ni, and Co, are micronutrients required for plant growth, while others, such as Cd, Pb, and Hg, have unknown biological functions[11]. In addition, some are toxic or poisonous even at low concentrations, and the collective term now includes As, Cd, Cr, Cu, Pb, Ni, Mn[12]. Heavy metals are required in tiny amounts by living organisms, but excessive levels can be harmful.

      Mercury, Pb, Cd, and As are known to be health hazards and have all been linked to severe health issues as a result of environmental contamination[13]. Iron, Cu (amine oxidases, dopamine hydrolase, and collagen synthesis), Mn (superoxide dismutase), and Zn (protein synthesis, DNA, and RNA stability) all have physiological functions, with Cr having minimal requirement (glucose homeostasis)[14]. Other heavy metal ions, even at small levels, are not thought to be necessary for human health.

      Cadmium, Pb, and Hg are common air pollutants that are emitted primarily as a result of industrial processes[15]. Despite the low atmospheric levels, they contribute to soil deposition and build-up. Heavy metals are persistent in the environment and can accumulate in food chains through bioaccumulation[16]. Most heavy metals are nonbiodegradable, have lengthy biological half-lives, and have the potential to accumulate in various bodily organs, causing adverse reactions[17].

      There is a significant connection between plant, animal, and human micronutrient nutrition and the absorption and effect of pollutants in these species. Leafy vegetables are widely used with other foods for culinary purposes, especially for increasing the quality of soups and for their nutritional value[18]. They are part of the daily diet in many parts of the world and are a source of vitamins and minerals. They are made chiefly of cellulose, hemi-cellulose, and pectin, which give them their texture and firmness. Consumer perception of better quality vegetables is subjective, as they consider dark green and large leaves to be characteristics of good quality. The external morphology of vegetables cannot guarantee the concentration of heavy metals because heavy metals rank high among the major contaminants of leafy vegetables[1]. The content of elements in vegetables is conditional and influenced by the properties of the soil and the capacity of crops to preferentially collect particular substances[19].

      The goal of this paper is to review heavy metal concentrations in vegetables produced in urban and peri-urban areas.

    • Heavy metal levels in urban areas are increasing as a result of fast and disorganised industrialization and urbanization[20]. Heavy metals are nonbiodegradable and long-lasting contaminants deposited on surfaces and absorbed by plants[21].

    • Heavy metals are transported to plants primarily through growth media (soil, air, and water). Many cities in developing nations have extremely high heavy metal concentrations in their soils[22]. Heavy metal absorption in soil has been linked to a variety of soil physical and chemical properties[23]. Biotic and abiotic factors influence the uptake and bioaccumulation of heavy metals in vegetables[24]. Temperature, water and edaphic conditions are some of the abiotic factors that significantly influence heavy metal uptake by crops.

      Heavy metal contamination can have a direct impact on crop physiology and development, and many examples of heavy metal toxicity have been identified[16]. Low biomass accumulation, chlorosis, inhibition of growth and photosynthesis, altered water balance and nutrient assimilation, and senescence, which ultimately cause crop death, are some of the impacts of heavy metals. Therefore, soil toxicity caused by heavy metals may pose a hazard to horticulture systems in urban areas[25].

    • The contamination of agricultural products with heavy metals has become a major concern around the world because of its potential negative health effects. In numerous studies, wastewater irrigation has been shown to increase heavy metal levels in receiving soils[26]. Several heavy metals are carcinogenic, including Cd, Cr, Ni, and Pb. Water pollution is fundamentally unavoidable in some locations owing to natural processes and anthropogenic activities[27]. Heavy metals such as Cd, Cu, and Pb are frequently found in wastewater from mining, electroplating, paint, and chemical labs[28]. These elements, when present in greater quantities, may damage public health conditions[29].

      Research results on cabbage, carrots and lettuce in Ghana stated that Cd and Pb concentrations rose considerably with the increasing rates of wastewater for irrigation to which Cd and Pb had been added to the water[30].

      Vegetables are commonly grown along rivers in metropolitan areas of developing countries[31]. Heavy metals have been found in the waters of such rivers on several occasions. The amount of elements absorbed by the plant is determined by several factors, including the plant's nature, the chemical composition of the pollutant, and the element's concentration in the soil[32].

      Post-harvest vegetables may be at risk from air pollution through shipment and commercialization, resulting in higher concentrations of heavy metals in the vegetables [33]. Long-term usage of treated and untreated sewage water has been associated with an elevated accumulation of heavy metals in vegetables [34].

    • Vegetables possess essential nutrients such as carbohydrates, proteins, vitamins, and metals. They absorb metals from the soil they grow in and the water used to irrigate crops[35]. Only a small portion of the ions linked with plant roots are absorbed by cells[36]. Various types of vegetables have varying abilities to acquire metals. Plants are known to respond to the quantities of easily transportable metals in soil, regardless of the mechanism involved in element absorption by roots[37].

      The classification of heavy metal contamination in vegetables varies[38]. This depends on climatic conditions and the type of heavy metals. In several species and ecotypes of natural plants, genetic variations and tolerances are well documented[39]. According to the research report of metal concentrations in vegetables from the Addis Ababa market, lettuce had the greatest Cd content, while cabbage had the lowest[40].

      In vegetables from Akaki farm (Addis Ababa), which was irrigated with industrial effluent, similar tendencies of increased metal accumulation in Swiss chard and low accumulation in cabbage were detected[41].

    • Further manmade trace metals include manures, sludge, fertilizers, and chemicals, which can impact heavy metal absorption by changing the soil's physicochemical characteristics[42]. Increasing concentrations of metals in soil enhance crop intake[43]. Farming areas near highways are also subjected to metal-containing aerosols, which pollute the air[44]. Particulates can be sprayed on the soil and absorbed by plants[45].

      Heavy metals emitted by industry and automobiles may be deposited on vegetable surfaces during processing, distribution, and commercialization[46]. For example, in Riyadh, increased amounts of heavy metals in vegetables are sold in the market owing to air deposition[47]. Air deposition can dramatically increase the levels of heavy metal contamination in vegetables regularly sold in Varanasi, India's marketplace[48].

    • The accumulation of heavy metals is harmful to biological systems and does not degrade through microbial degradation[49]. Harmful substances such as Pb, Co, and Cd can be distinguished from other contaminants because they cannot be biodegraded but may accumulate in living beings[50]. Heavy metals cause significant health risks to several species, with soil residence for a longer period of time[11]. Antioxidants are also recognized to influence plant development, ground cover, and soil microbiota[51]. Contaminants cannot be decomposed but are forcibly converted into harmless molecules[52]. In recent research works, it was determined that the effect of antioxidant supplementation followed heavy metal exposure[31]. They suggest that antioxidants may play an important role in abating some health hazards of heavy metals in connection with an interaction of physiological free radicals (health effects). The contamination of the physical and biological components of the environment adversely affects the whole systems of fauna and flora[43].

    • Arsenic has the chemical symbol 'As' and is a semimetallic element[52]. It is a pollutant present in the environment that is highly harmful to humans and other living species[53]. It is also a very hazardous element found in a variety of forms, and the toxicity varies depending on the conditions. The pH, redox conditions, mineral composition, and microbial activity all have their own impacts. The contaminated water used for drinking, food preparation and irrigation of food crops poses the greatest threat to public health from arsenic. Long-term exposure to As from drinking water and food can cause cancer and skin lesions[54].

    • The heavy metal most commonly associated with poisoning of humans is Pb[55]. Lead poisoning may occur as a result of industrial exposure, air or water pollution, foods, medicines, improperly coated food containers, or the ingestion of lead-based paints. Additionally, heavy metals, such as Pb, are a group name for metals that have been associated with contamination and potential toxicity[56]. Lead may be found in a variety of forms in natural sources worldwide and is currently one of the most extensively and equally distributed trace metals[57]. Lead from automobiles, dust, and fumes can pollute soil and the environment[58]. When present in high concentrations, it can be hazardous to humans[59]. Its contamination is highly damaging to biological systems and does not degrade through biodegradation[60].

      Lead toxicity in the ecosystem occurs irreversibly, and it potentially causes risks to human health, such as brain developmental delay[61].

    • Mercury is found naturally in a variety of forms[11]. In the soil ecosystem, there are three soluble forms of Hg. It is an environmental contaminant that may enter via the food chain in fish, animals, and humans[62]. Mercury salts and organomercury compounds are among the most toxic elements in our environment[63]. The level of toxicity is highly dependent on the kind of chemical and the redox state of Hg[64]. Mercury pollution in the environment occurs in a variety of ways, including petrochemicals, mining, and painting[65].

      Home bleach, acid, and caustic chemicals (e.g., battery acid, household lye, muriatic acid (hydrochloric acid)), and Hg-containing instruments are among the most prevalent contributors of Hg[66]. In general, Hg naturally occurs in nature and is essential to life but can become toxic through accumulation in organisms. Mercury is the most common heavy metal that can pollute the environment[59].

    • Due to their toxic effects, heavy metals are extremely dangerous to vegetables, and they are among the pollutants encountered on the outside and inside structures of fresh fruits and vegetables[67]. Because of their aqueous solubility, several heavy metals are especially dangerous, and currently, they are widely used in industry[68].

      Over several years, factors linked to the potential health impacts of Cd, Pb, and Hg exposure have been studied in occupational settings, utilizing both animals and humans exposed to natural pollution. The types of harmful health effects are well recognized, but there are limits for specific outcomes[69].

      Chronic low-level thrash metal consumption has negative effects on humans and other animals since there is no efficient mechanism for removing them from the body. Metals such as Pb, Hg, Cd, and Cu accumulate as poisons[55]. Vegetables absorb heavy metals by absorbing them from contaminated soils as well as deposits on sections of vegetables vulnerable to toxic air[55]. High intake of unsafe levels of heavy metals in food may upset many biological and biochemical processes in the human body[70]. The elements Hg and Pb have been linked to the development of malformations in children. Long-term Cd exposure causes kidney failure and ovarian distortions[8].

      Diet is the most common source of Cd in the general community, encompassing more than 90% of the total consumption[71]. Under some environmental conditions, Cd accumulates in soils and catchments and increases the risk of future exposure through food chains. The Collaborative Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) Food Standards Programme's Codex Committee on Food Additives and Contaminants has established tentative thresholds for typical everyday consumption[72]. As a result, the consumption of heavy metals accounts for much less than 10% of the theoretical maximum daily intake (TMDI)[73]. Arsenic, Cr, Fe, and Pb are now more dangerous to one's health than the other heavy metals[74]. However, the levels of heavy metals in the vegetables analyzed would not be sufficient to determine health consequences. All this is determined by the consumers' eating habits.

      Compared to the global daily consumption of 50 g of green vegetables, in Addis Ababa, Ethiopia, the mean consumption of vegetables per day is 5 g[75]. As a result, the intake of metals from the examined vegetables is substantially lower than the TMDI or presumptive tolerated weekly intake (PWTI), which can be used to indicate user consumption and accompanying health risks[76].

      To determine the total exposure level in the population, the rate of contamination and consumption must be monitored regularly. Reduced crop pollution and improved food security can be achieved by lowering pollutants, enlightening vegetable cultivation and commenting on the processing[77]. The disastrous feature of heavy metal contamination of the environment is that they can only be changed from one oxidation state to another[78]. The transport of Cd via soil to the food chain is affected by a variety of factors, including the type of crops, soil characteristics, pH, and organic matter content. Cadmium sorption to soil particles is stronger in neutral or alkaline soils than in acidic soils, resulting in higher Cd concentrations in the solution[79]. Excessive levels of Pb and Cd metals in the diet have been linked to a variety of disorders, including the cardiovascular, renal, neurological, and skeletal systems[55]. Certain toxic substances have also been connected to cancer, mutagenesis, and teratogenesis[80]. Cadmium has also been recognized as a possible human carcinogen with the potential to cause lung cancer. Lead has developmental and neurobehavioral impacts on fetuses, babies, and children and raises cardiac output in individuals[81].

      Contaminants, including Cd, Pb, and Hg, are frequent air pollutants that are discharged (mostly into the atmosphere) as a result of numerous industrial operations. Excessive exposure to air pollution from industrial operations, transportation, and energy generation is one of the repercussions of the current stage of economic development and the need for enhanced quality of life[82].

    • Nitrogen, P, K, total dissolved solids, viruses, trace organic compounds and metals, particularly heavy metals, are all present in the combination of industrial and home wastewater[83]. Many heavy metal ions, such as Co, Cu, Fe, Mn, Mo, V, Sr, and Zn, are required in small amounts by living things[84]. Cadmium, Cr, Hg, Pb, As, and Sb are nonessential heavy metals of special importance to surface water systems[85].

      Contaminants are emitted locally from a variety of sources, including industry (primarily nonferrous industries, power plants, iron, steel, and chemical industries). Heavy metal contamination in water is mostly produced by point source pollution from mining and a wide range of businesses[86].

      The greatest quantities of metals, including Zn (113 mg/kg), Cr (47.8 mg/kg), Pb (17.7 mg/kg), and Cd (0.250 mg/kg), have been reported from samples collected from farms in Ziway, Burayu, and Addis Ababa[24].

      Table 1.  Mean metal content in vegetable field soils.

      Metals (mg/kg)Ziway KentolaZiway EthiofloraBurayuKuskuam UpperKuskuam LowerRecommended maximum
      level in soil (mg/kg)
      Cd0.180 ± 0.0700.220 ± 0.0400.140 ± 0.0800.250 ± 0.0800.190 ± 0.0503
      Cr3.0 ± 0.068.44 ± 1.2947.78 ± 8.9131.24 ± 1.4932.6 ± 5.09100
      Pb6.02 ± 0.347.12 ± 2.7517.66 ± 1.6616.38 ± 3.0111.17 ± 1.46100
      Zn49.98 ± 0.2768.42 ± 4.7888.47 ± 13.04112.7 ± 8.3478.02 ± 8.27300
      Source: reference [87]

      Wastewater irrigation causes heavy metal buildup in soil and results in heavy metal accumulation in vegetables[87]. Heavy metal concentrations varied across vegetables, reflecting differences in their ability to absorb. As a result, the Cd, Pb, and Ni contents in all vegetables are above the permissible limits for human consumption (Table 2). Consumption of vegetables containing high quantities of heavy metals can lead to higher levels of bioaccumulation, resulting in health problems.

      Table 2.  Concentrations of certain trace elements reported in the Bulbula and Kera streams and other surrounding agricultural soils in Ethiopia.

      ComponentBulbulaKeraRecommended maximum contents
      River (μg/Liter)Soil (total)River (μg/Liter)Soil (total)Irrigation waterSoil (total)Vegetables (mg/kg)
      As1.75.19< 1.006.8100200.2
      Cd0.070.71< 1.000.441030.2
      Co2.6927.95< 5.004350500.3
      Source: reference [40]
    • Fruits

      The quality of fresh fruits produced in very polluted areas of Romania was evaluated, and the level of heavy metals was reported to be modest[88]. Most samples showed medium values of total and mobile heavy metal concentrations (Cd, Cu, Pb, and Zn) that exceeded the maximum permissible limits. Individuals are encouraged to take more fresh fruits, which are high in vitamins, minerals, and fiber and are excellent for their wellbeing[89]. However, these fruits possess both necessary and harmful metals in different amounts. It is known that plants acquire metals from polluted soil along with accumulation on plants[90].

      Onion and Leek

      Relatively higher levels in the onion's bulb/leaves were found for Fe, Mn and Zn. Significant anthropogenic contamination was noted for the metals in the present study. Metal levels in all onion varieties showed no significant cancer or no-cancer risk[83]. The concentration of heavy metals in the aqueous phase showed a reduction in heavy metals in humans. The toxic substances Cd, Cr, and Pb in onion leaves were reported to be in the range of 0.667−0.933, 3.870−7.870, and 5.870−7.537 mg/kg, respectively.

      Tomato and Capsicum

      In semiurban and rural regions of visakhapatnam, southern India, Pb, Zn, Ni, and Cu content in vegetables were measured, and Ni and Zn were found to be greater in industrial areas, but Cu concentrations in semiurban areas were found to be 2−3 times higher in tomatoes than in rural vegetables[91]. The additional elements of Pb and Zn in industrial and semiurban regions were found to obtain inputs from both ambient and soil sources in all crops.

      Leafy vegetables

      The levels of Pb, Cu, Cr, Zn, and Cd in spinach, coriander, lettuce, radish, cabbage, and cauliflower growing in pollutant areas near an industrial zone of Pakistan were reported[92]. The results showed that the Cu, Zn, Cr, Pb, and Cd concentrations were below the permissible limits suggested by the United FAO/WHO Advisory Group on Food Additives.

      However, when compared with other portions of vegetables, the leaves of spinach, cabbage, cauliflower, radish, and coriander revealed greater quantities of Cu (0.923 mg/kg), Cd (0.073 mg/kg), Cr (0.546 mg/kg), Zn (1.893 mg/kg) and Pb (2.652 mg/kg), as previously reported[93]. This finding revealed that considerable differences in elemental concentrations occurred among the vegetables considered. Similarly, research was conducted in two popular Pumpkin leaves and Chinese cabbage cultivated in Tanzania's Morogoro municipality, and two heavy metals, Pb and Cu, were measured[94]. The results showed that there was a significant difference in the two metals across the site. The Pb and Cu levels in the two vegetables were found to be lower than the optimum acceptable limits specified by the FAO/WHO.

      Table 3.  Estimated Pb and Cd contents in vegetables worldwide.

      VegetablesNigeriaEgyptPakistanIndiaTanzaniaGreeceVegetablesAddis AbabaGondar
      Lady's finger1.031.41
      Source: references [92, 95, 96]

      In Akaki, the highest Co content was detected in potato planted with wastewater, followed by lettuce and Swiss chard[97]. Lettuce from Kera had the largest quantities of Cr and Fe, whereas kale from the same location had the highest concentrations of Cu, Ni, and Zn[40]. Swiss chard and carrot from Akaki had the greatest levels of Mn and Pb, respectively (Table 4). As a result, lettuce, Swiss chard, and kale appear to be the most metal-accumulating vegetables in Addis Ababa, Ethiopia[98]. The concerns of heavy metal pollution in Addis Ababa's vegetable fields, as well as its accumulation on produce, have been recognized[99]. However, the research was limited to the issues of heavy metal deposition on vegetables as a result of industrial pollution. The levels of heavy metals in Addis Ababa's urban area are the result of geogenic conditions from the soil crust[100].

      Table 4.  Trace element content in the leaves of crop varieties planted using urban industrial effluent (Addis Ababa).

      CropFarmMetal/metalloid concentration
      AsCdCo CrCuFeMnNiPbZn
      (µg/kg) (mg/kg)
      CabbageKera< 1000< 50620.893.0373290.80.2131.8
      Peacock< 1,000< 501331.713.3173250.910.2931.81
      Akaki< 1,000< 501310.682.5219301.370.3732.49
      Swiss C.Kera1,210786812.058.0652737.52.101.7956.19
      Peacock< 1,000< 503171.047.884.61670.890.6148.91
      CarrotMekanisa< 1,000591300.827.68403532.440.9144.87
      Peacock< 1,000< 50840.287.79205290.980.5429.9
      Akaki< 1,000842560.828.99469571.662.1559.03
      KaleKera< 1,0001303080.999.923311264.640.5363.71
      Akaki< 1,000< 501871.13.0517330.51.310.3735.08
      PotatoKera< 1,000782560.79.66364.5661.41.828.25
      Bulbula< 1,000751651.216.24351540.710.3947.8
      Recommendation Levels (mg/kg)0.430.22.3425.567.90.399.4
      Source: reference [98]

      Cabbage crops accumulated the lowest content of heavy metals compared to other vegetables. However, the Cr concentration in all vegetables surpassed the permissible level[101]. The Cu, Mn, and Ni concentrations in all vegetables were determined to be less than the maximum limit. The Cd level was higher in leafy vegetables such as lettuce, Swiss chard, spinach, and radish.

      Generally, a recent investigation on the heavy metal concentrations of vegetables from the Addis Ababa market found that lettuce had the highest Cd content and cabbage had the lowest[102]. Except for potato, lettuce, and spinach, all other vegetables had lower Zn concentrations than the maximum limits for vegetables. The Fe concentration was found to be lower in radish, tomato, cabbage, and beans, but all other vegetables contained more Fe than the upper limit[103]. High Fe concentrations in vegetables might be instigated by the metal industry and the wastewater that reaches the river. Certain withered leaves and necrotic patches were noted on some plants due to heavy metal toxicity[104].

      The concentrations of Cd, Cr, and Zn in lettuce were greatest at the Kuskuam farm (which uses tap water from the public water supply) compared to other farms, followed by the Burayu field (utilizes water from the Gefersa River)[92]. Burayu farm, on the other hand, has a larger concentration of Pb than other farms, while Ethioflora from Ziway (water from Lake Ziway) has the lowest concentration of all metals[105]. The lettuce from Burayu farm had the greatest mean concentration of Pb, followed by lettuce from Kuskuam and Ethiopian Kale in Burayu farm. Vegetables can absorb heavy metals into their systems when exposed to more acidic conditions[106]. The concentration of Pb in all vegetables from different farms was not significantly different. As presented in Table 5, Pb-containing vegetables may contribute to high Pb levels in the body, increasing the risk of anemia and neurological problems[107].

      Table 5.  Total load of heavy metals in vegetables treated using Akaki river water.

      VegetablesTotal metal load (µg g−1)
      Beet0.254 ± 0.0810.28 ± 1.9432.25 ± 3.090.3 ± 5.8161.0 ± 6.02566.20 ± 8.47.57 ± 1.06
      Potato0.281 ± 0.147.18 ± 1.0635.13 ± 3.1105.00 ± 6.2148.05 ± 5.8634.04 ± 9.45.99 ± 1.68
      Carrot0.198 ± 0.068.05 ± 1.0822.18 ± 2.680.12 ± 5.295.10 ± 6.2426.01 ± 8.84.51 ± 1.08
      Onion0.271 ± 0.128.58 ± 1.625.13 ± 2.465.9 ± 4.2107.9 ± 8.06578.0 ± 9.43.67 ± 1.02
      Tomato0.115 ± 0.064.91 ± 1.413.21 ± 1.845.11 ± 3.869.17 ± 4.08322.3 ± 8.42.21 ± 0.08
      Pepper0.180 ± 0.085.55 ± 1.617.21 ± 2.649.15 ± 3.856.29 ± 2.6429.26 ± 8.85.38 ± 1.02
      Head cabbage0.101 ± 0.044.11 ± 10814.20 ± 1.848.47 ± 3.645.4 ± 3.8245.2 ± 6.41.95 ± 0.06
      Green-bean0.199 ± 0.046.12 ± 1.212.52 ± 1.662.54 ± 6.686.25 ± 6.04251.54 ± 6.22.1 ± 0.08
      Lettuce0.345 ± 0.1824.11 ± 2.424.25 ± 2.4108.94 ± 8.8145.6 ± 6.02511.27 ± 8.22.95 ± 0.08
      Maximum limits for vegetables0.22.399.4425.567.9
      Source: reference [101]

      Table 6.  The percentage of metal influxes in vegetable tissue sourced from soil.

      VegetablesMetalsVegetable farms
      KuskuamBurayuZiway Ethioflora
      Ethiopian kaleCd47%42%11%
      Swiss chardCd26%2%
      Source: reference [108]

      Research was conducted at Peacock farm, which was irrigated by the Bulbula River, and Kera farm, which was irrigated by the Kebena River. Hence, as per the authors' observations, cabbage was the smallest metal absorbent[40]. Additionally, the metal concentrations were greater in lettuce and Swiss chard cultivated at Kera than on Peacock farms. The As, Cr, Fe, and Pb contents in these vegetables have surpassed maximum allowable levels in a few cases, whereas cabbage has a Cu shortage.

      Table 7.  Metal content in leafy vegetables in Addis Ababa's (Ethiopia) Kera and Peacock farms.

      CabbageLettuceSwiss chardRecommended maximum
      level for vegetables
      Source: references [109, 110]

      Research results reported that there is a significant accumulation of heavy metals in vegetables watered with effluent[111]. The concentrations of Fe, Mn, Cu, and Zn in wastewater-irrigated vegetables were 116−378, 12−69, 5.2−16.8, and 22−46 mg/kg, respectively. Mint and spinach had the greatest amounts of Fe and Mn, while carrot had the highest levels of Cu and Zn. According to the findings of this study, both adults and children who eat vegetables produced in wastewater consume large amounts of these elements. Contaminated water includes significant quantities of toxic substances, which causes problems[112]. A high buildup of toxic substances due to wastewater irrigation may contaminate not only the land but also the food safety standards[113].

      Vegetables, generally, are one of the plants that absorb contaminants to meet their body's requirements based on their genetic composition, the soil in which they are cultivated, and the water with which they are irrigated[114]. The differences in heavy metal content across vegetables were also ascribed to the vegetable's self-selectivity for a certain type of heavy metal[115]. Based on availability and soil qualities, the levels of heavy metals in various crops varied from one area to the other. Although significant heavy metal concentrations in soils were identified, availability may be restricted by the presence of clay in the northern parts of Addis Ababa. A high amount of metals in the soil needs careful consideration since it might cause serious problems if soil qualities are changed to acidic conditions[116].

    • According to the differences in the amount of diminution in the toxic metals, vegetable washing is an important activity to remove heavy metals. Reasearch indicates that vegetables can be cleaned adequately before eating to lessen the health risk[47]. The amounts of Pb, Cd, Cu, and Zn in washed and unwashed vegetables were measured. However, the results showed that consuming heavy metals, especially leafy vegetables, does not pose a health risk to consumers (Table 3).

      However, in Agra India, research was performed to evaluate the accumulation of airborne heavy metals in edible parts of crops, and the results demonstrated that unwashed vegetables had a higher extent of hazardous substances than washed vegetables[117].

    • Transportation and marketing of vegetables in polluted environments may increase the amounts of heavy metals. Eating vegetables directly from producing areas may be less harmful to human health than the intake of vegetables from contaminated public market places. Contaminants are harmful, but the negative effects appear obvious only after long-term consumption of polluted vegetables. It was proposed that toxic substances in vegetables and other food products be monitored regularly to avoid the excessive development of these pollutants in the human food chain. Appropriate safeguards should also be followed during vegetable shipment and distribution.

      Heavy metal levels of Zn, Mn, Cu, and Pb in vegetables taken from Nigerian trash sites were shown to be high. Accordingly, cars are a key source of heavy metals along roadside areas. The extent of heavy metal deposition on vegetable surfaces differed according to the morpho-physiological character of the plants[8].

    • Heavy metal levels in boiled vegetables are greatly diminished. After boiling vegetables in water for 15 min, the Cd content in cauliflower purchased from Gariahat, Maniktala, VIP market, Shyambazar, and Brinjal (India) was purchased from Gariahat, Maniktala, VIP market; Shyambazar fell below the safe level. Even after boiling, cauliflower from Lake market and VIP market had a Cd level that was somewhat more than the acceptable value[118]. After washing and boiling, the Pb concentration of all vegetables remained greater than the permissible level. The Cu level in unwashed Brinjal (Lake market, Maniktala) and Indian Spinach (VIP market, Shyambazar) surpasses the safe limit. However, the Cu level of boiling vegetables did not surpass the permissible limit. Chromium levels in brinjal and Indian spinach were found to be higher than the acceptable limit in a few samples. The only sample of Red Indian spinach bought from Maniktala exhibited a greater level of Cr following washing. The Pb concentration in all vegetables (washed, unwashed, and boiled) was above the acceptable standard (0.2 mg/kg)[119].

    • Restoration strategies of certain microbes, such as biosorption, can breakdown and detox some pollutants[120]. While these life systems become less resistant to external changes than other earlier systems, they are believed to be more affluent[121]. Some of the methods are stated below.

    • Phytoextraction is also called phytomining. It is defined as the absorption and transfer of pollutants by the root system into subterranean sections of the plants[122]. It can be performed by the utilization of plants for heavy metal removal from the contaminated matrix (soil and water) through their uptake into the harvestable parts of the plant. For example, chromium is toxic to higher plants at concentrations above 100 μM/kg dry weight. Unlike phytostabilization, by which plants only temporarily contain heavy metals and these heavy metals still remain belowground, phytoextraction is a permanent solution for the removal of heavy metals from polluted soil. Therefore, it is more suitable for commercial application.

    • Phytostabilization is the use of specific plant species to immobilize pollutants in soil and groundwater through absorption and accumulation in plant tissues[122]. It involves the reduction of the mobility of heavy metals in soil. Immobilization of metals can be accomplished by decreasing wind-blown dust, minimizing soil erosion, and reducing contaminant solubility or bioavailability to the food chain. It is also a promising technology for cleaning polluted sites by using plants to extract heavy metals from contaminated soil and accumulate them in roots, stems, and branches. Various species of grass, such as red fescue (Festuca rubra L.) are the most useful in the process of aided phytostabilization of heavy metals in soils.

    • Rhizofiltration is the adsorption or deposition of pollutants in solution around the root zone on plant roots[11]. It is also the adsorption or precipitation of dissolved compounds onto plant roots or absorption into the roots. A few examples of plants that are employed for rhizofiltration are sunflower, tobacco, spinach, rye and Indian mustard. Plant species in addition to hyperaccumulators can also be used, as heavy metals need not be translocated to the shoots. Rhizofiltration is a form of phytoremediation that involves filtering contaminated groundwater, surface water and wastewater through a mass of roots to remove toxic substances or excess nutrients.

    • Bioremediation is any procedure that employs microorganisms, fungi, and green plants[123]. Bioremediation methods are categorized as either in situ or ex situ. It is also a technique for removing/converting harmful contaminants such as heavy metals into less harmful substances; removing toxic elements from the contaminated environment; or degrading organic substances and ultimately mineralizing organic substances into carbon dioxide, water, nitrogen gas, etc. Microbial bioremediation of heavy metals is emerging as an effective technique. Microbial bioremediation is a highly efficient and environmentally friendly procedure that also reduces the cost of the cleanup process associated with heavy metal contamination. It relies on stimulating the growth of certain microbes that utilize contaminants such as oil, solvents, and pesticides for sources of food and energy. These microbes convert contaminants into small amounts of water, as well as harmless gases such as carbon dioxide. In situ bioremediation treating polluted material on site and ex situ bioremediation require removing the contaminants to be handled elsewhere[124]. Bioventing, commonly ascribed, bioreactors, composting, bioaugmentation, rhizofiltration, and biostimulation are some of the types of biomonitoring systems[125].

      However, not all pollutants are easily removed by bioremediation utilizing microorganisms. Heavy metals, such as Cd and Pb, are not quickly digested or caught by microbes[126]. The incorporation of elements such as Hg into the food chain may aggravate the situation. In these cases, phytoremediation is advantageous because natural or transgenic plants may bioaccumulate these poisons in their aboveground sections[127].

    • Phytoremediation is the inherent capacity of some plants known as chelators to accumulate, decompose, or make pollutants benign in soils, water, or air[128]. It is applied to underground waters, surface waters and waste waters. Rhizofiltration is used to remove radioactive substances or metals from contaminated waters. The plants used in this method are directly planted on contaminated soil, and contaminant adaptation is ensured. To eliminate heavy metals from contaminated fields, phytoremediation is considered a clean, inexpensive, and nonenvironmentally damaging method[129]. It is also a plant-based approach that involves the use of plants to extract and remove elemental pollutants or lower their bioavailability in soil. Plants have the ability to absorb ionic compounds in the soil, even at low concentrations, through their root system. Green plants have been promoted for in situ soil phytoremediation, which has become a prominent research and development area[130]. However, another important drawback of phytoremediation is that it takes a lot of dedication as the process is based on growing plants, toxin tolerance, and biomagnification potential[131]. Arsenic is absorbed by the sun flower (Helianthus annuus) or the Chinese Brake fern (Pteris vittata), both of which are hyperaccumulators[132]. Arsenic is stored in the leaves of the Chinese Brake fern[133]. According to Greger & Landberg[134], willow (Salix viminalis) has a high phytoextractor potential for Cd, Zn, and Cu. Because hawthorn has several unique attributes, such as high metal transport capacity from root to shoot and a large quantity of plant biomass.

      Cadmium and Zn were explored using Alpine pennycress (Thlaspi caulescent), a hyperaccumulator of both metals reaching hazardous levels in many plants[135]. On the other hand, the presence of Cu appears to inhibit its development. Lead may be removed from the environment by planting Indian mustard (Brassica juncea), Ragweed (Ambrosia artemisiifolia), and Hemp Dogbane (Apocynum cannabis).

      Additional statements were also reported regarding the elimination of several heavy metals, such as Cu, Zn, Ni, and Cr, by free and immobilized microalgae[136]. For repeated applications of algal beads (microalgal beads) for the removal of heavy metals and recovery, an exposure decomposition process was designed. Investigators observed that alginate-immobilized C. vulgaris pearls managed to remove Cu (more than 95% removal) from industrial effluents[137].

    • Phytovolatilization is the process by which plants absorb pollutants from the soil, convert them to volatile forms, and then expel them into the atmosphere[138]. It is also a process in which plants take up contaminants from soil and release them in volatile form into the atmosphere through transpiration. The process occurs as growing plants absorb water and organic contaminants. It is described as the utilization of plants, both terrestrial and aquatic, in their roots to absorb, concentrate, and precipitate pollutants from contaminated water sources. In recent years, heavy metal pollution in saline soil has become increasingly severe due to the rapid development of industry and agriculture. Plants absorb and convert toxic contaminants into less toxic forms. The remediation of heavy metal-contaminated sites must be viewed seriously, as they affect animal and human health. Rhizofiltration can be utilized for heavy metals such as Pb, Cd, Cu, Ni, Zn, and Cr that are largely retained inside plants[139]. Sunflower, Indian mustard, tobacco, rye, spinach, and corn have all been examined for their potential to eliminate Pb from water. Indian mustard has a biomagnification value of 563 for Pb, which is necessary to eliminate Pb at a wide range of concentrations (4−500 mg/L)[139]. The flexibility to employ both land and marine plants for in situ or ex situ use is one of the benefits of root uptake[140]. An additional benefit is that pollutants are not transported to the plants.

      As a result, species other than hyperaccumulators can be employed. Aerial plants are favored, as their root systems are flexible and considerably longer, increasing the amount of plant root zone[141].

    • Various factors can influence heavy metal availability and uptake efficiency by crops[142].

    • Different plants or types are evaluated, and the ones with the best restoration characteristics are chosen[143]. Vegetation type characteristics influence chemical absorption. The selection of appropriate plant species that hyperaccumulate heavy metals and produce large amounts of product using current crop production[144].

    • Agroecological approaches (pH correction, inclusion of chelators, fertilizers) are being proposed to improve rehabilitation[145]. The quantity of lead taken by plants, for instance, is controlled by soil pH, vegetable material, and phosphorus level[146]. The pH of the soil was corrected with calcium to a range of 6.5−7.0 to minimize lead uptake.

    • In phytoremediation, the root zone is of particular relevance. It can absorb pollutants and store or metabolize them inside plant tissue[141]. Another phytoremediation technique is the degradation of pollutants in the soil by plant enzymes secreted from the roots. A morphological adaptation to drought stress is an increase in root diameter and decreased root elongation as a reaction to the dry soil's decreased permeability[147].

    • Environmental factors influence vegetative absorption. Temperature influences growth stimulants and, as a result, root length. The root structure in the field contrasts with that in the glasshouse. The achievement of bioremediation, specifically phytoextraction, is dependent on the presence of a pollutant hyperaccumulator[148]. Knowing mass conservation assessments and the metabolic destiny of toxins in crops is critical to demonstrating phytoremediation's potential application[149].

    • Rhizobial studies under controlled and field conditions are required to investigate the antagonistic and synergistic effects of multiple heavy metal ions in soil solution and polluted water[150]. Soil microbial studies are also required to recognize microbes that are strongly linked to metal precipitation. The majority of the toxic substances discovered have toxicity profiles, but the negative effects never become evident[151]. As a result, it is proposed that constant monitoring of heavy metals in plant tissues is required to prevent excessive accumulation in the human food chain[8].

      Supervision and evaluation of the levels of heavy metals in vegetable crops require extensive study to minimize the health hazards to humans. However, there is no comparison of the accumulation of heavy metals in the air and trade sites in the literature reviewed[152].

    • Vegetables are a major part of nutrition because they comprise carbohydrates, enzymes, minerals, and natural fibers that are important for health. Environmental change and pollution of the food chain are unavoidable as human activities rise. The absorption of toxic substances by plants in contaminated soils has been investigated. Among food quality management practices, heavy metal content determination is critical. Because of the high attention to the threat of the substances in food production, national and international restrictions have been decided. This is to lower the concentrations of pollutant metals in foodstuffs. Most contaminants are non biodegradable, have longer biomedical splits, can accumulate in various body parts and have adverse environmental effects. There is a strong correlation between plants, animals, and human beings on the notation of micronutrient nourishment and absorption of toxic substances. The composition of crop components also depends on the soil conditions and the type of crop cultivated. Metal pollutants in the soil, water, plants, and air are major issues due to possible inferences on human health and environmental existence. To maintain scarce natural resources and genetic pools, economical and easily accessible technologies are needed, especially for low- and middle-income countries.

      Over the last decade, great efforts have been made to recognize flora and fauna and their courses of heavy metal uptake and hyperaccumulation trends. The introduction of heavy metals into the environment (soil, water, plants, and air) is profoundly laden with the concern given for the potential implications of the substance on humans and the environment. Thus, to secure biodiversity and genetic resources, operative and affordable policies and strategies should be applied.

    • The author acknowledges the anonymous reviewers for their valuable input for the manuscript.

      • The author declares that there is no conflict of interest.

      • Copyright: © 2022 by the author(s). Published by Maximum Academic Press on behalf of Nanjing Agricultural University. This article is an open access article distributed under Creative Commons Attribution License (CC BY 4.0), visit
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    Gelaye Y. 2022. Noxious substance content of vegetables grown in urban and peri-urban areas. Food Materials Research 2:5 doi: 10.48130/FMR-2022-0005
    Gelaye Y. 2022. Noxious substance content of vegetables grown in urban and peri-urban areas. Food Materials Research 2:5 doi: 10.48130/FMR-2022-0005



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