| | Region | Common heavy metals | Major sources | Risk/implications | Author |
| | East | Pb, Al, Zn, Cr, Fe, Mn, Cu, Co, As, Ni, Hg | Heavy metals and metalloids from municipal and industrial wastes in Onitsha/Awka and Abagana in Anambra and Abia States, respectively, mining and quarrying (e.g., Pb-Zn mining and igneous rock quarrying and limestone mining at Ishiagu and Nkalagu, respectively, in Ebonyi State), air pollution from transportation, agrochemicals | Potential heavy metal toxicity in the body system that can lead to hemoglobinuria, gastrointestinal disorders, ataxia, pneumonia, diarrhoea, stomatitis, and paralysis | Orisakwe et al. [31]; Ihedioha et al. [9]; Asomugha et al. [42]; Odika et al. [7]; Jaishankar et al. [65]; Nduka et al. [52] |
| | South | Zn, Cd, Pb, Fe, Cu, Cr, Co, and Mn | Petroleum extraction and refineries, e.g., consumers of seafood from these contaminated sites in Ogoniland may be exposed to metal pollution | Environmental degradation resulting to excessive social unrest and destruction and incessant harm to the physical, social, environmental, and economic health of its inhabitants | Nkpaa et al. [51]; Worgu [48] |
| | West | Pb, Al, Zn, Cr, Fe, Mn, Cu, Co, Mo, Se, As, Ni, Hg | Aerial deposition by emissions from Lagos traffic, leaching and runoffs of contaminants from Ekiti State dumpsites. Contaminated freshwater bodies in Osun State. Accumulation of heavy metals from battery waste in topsoil, surface water, and garden grown maize at Omilende area, Olodo, Nigeria | Long-term consumption of (leafy) Amaranthus from Lagos highway soils poses potential health risk due to its heavy metal concentrations. Health risk index (HRI) and daily intake of metal (DIM) estimation indicate higher health risk indexes in vegetables containing Pb, Ca, and Hg. Osun freshwater bodies showed high carcinogenic risk from high concentrations of heavy metals | Atayese et al. [66]; Nduka et al. [52]; Adeyeye [53]; Balkhair and Ashraf [67]; Titilawo et al. [68]; Afolayan [69] |
| | North: | Pb, Zn, Cr, Fe, Mn, Cu, Co, Ni, | Some heavy metals are introduced into the environment from farmyard and chemical fertilizer application (agrochemicals). Others include domestic by-products, worn automobile tires, roofs, brake linings, and waste food. There are also iron mining sites (Itakpe, Kogi State). Sample of tested sediment from the river Ngada, Maiduguri in Borno State revealed provocative amounts of heavy metals. Evidence of mobility of heavy metals from dumpsites to farmlands through leaching and runoff in Lafia, Nasarawa State | Increase concentration of zinc in pasture fields. Anthropogenic sources usually produce heavy metals that are high in instability and solubility and in turn, result in high bioavailability which increases potential health risk. Decrease in soil productivity by high Pb concentration, while extreme low concentration can inhibit some essential plant processes such as mitosis, water adsorption, and photosynthesis. This can lead to brown short roots and stunted growth/foliage. Toxicity of heavy metals on the other hand can lead to reduced ability in leguminous plants to fix molecular nitrogen | Bawuro et al. [57]; Agbenin [70]; Anguelov and Anguelova [64]; Armah et al. [71]; Tangahu et al. [72]; Khan et al. [73]; Bhattacharyya et al. [74]; Guala et al. [75]; Singh et al. [76]; Akan et al. [77]; Opaluwa et al. [30, 61] |
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