Contamination and human health risk due to toxic metals in dust from transport stations and markets in the Kumasi Metropolis, Ghana

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May, 2019
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Heavy metals are very harmful to human health and their increasing contamination of dust in the urban areas calls for serious attention to them. The aim of this study was to determine the concentrations and assess the potential human health risk associated with exposure to selected heavy metals in dust from transport stations and markets within the Kumasi metropolis, Ghana. A total of 50 dust samples from transport stations and markets were collected by sweeping ground surface dust and analyzed for Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), Zinc (Zn), Iron (Fe), Mercury (Hg) and Antimony (Sb). The concentrations of Hg were determined by Atomic Absorption Spectrophotomery using a Lumex RA-915M Zeeman Automatic Mercury Analyzer while the levels of other metals were determined by using X-ray Fluorescence analyzer (Niton XL3t GOLDD+). The concentrations of As, Cd, Cr, Hg, Cu, Ni, Pb, Zn, Fe and Sb in transport stations ranged from below detection to 9.66, below detection to 37.13, below detection to 260.11, 0.01 to 0.62, below detection to 143.77, below detection to 47.62, below detection to 61.73, 48.89 to 218.61, 3768.97 to 40936.07 and below detection to26.01 mg/kg respectively.The concentrations of As, Cd, Cr, Hg, Cu, Ni, Pb, Zn, Fe and Sb in markets ranged from below detection to 6.20, below detection to 14.61, below detection to 232.90, 0.01 to 1.38, below detection to 181.85, below detection to 44.79, below detection to 72.10, 59.29 to 293.68, 8283.66 to 34953.63 and below detection to 21.72 mg/kg respectively. The study revealed no significant difference between the mean concentrations of heavy metals in dust from transport stations and markets at 95% confidence limit of T-test analysis (p>0.05). The mean geo-accumulation, contamination factor and modified degree of contaminations indicated that dust from both transport stations and markets were moderately to extremely polluted by metals compared to their abundance in the dust of the control site v (KNUST Botanic Gardens). Mean enrichment factors indicated that metals were highly enriched in the dust and originated from anthropogenic sources. Pollution load index which ranged from 1.39 to 12.55 for transport stations and from 1.48 to 15.62 for markets revealed high pollution load. The hazard index (HI) and carcinogenic risk index (CRI) were used to assess human health risk. Hazard indices for all the metals were less than the safe limit of 1, signifying no potential non-carcinogenic risk for both children and adults. Exposure to multiple metals was observed as a major concern of non-carcinogenic risk to children. Among the metals assessed for carcinogenic risk, the CRI of Cd in both transport stations and markets exceeded the safe limit of 1x10-4 for children. Health risk assessment indicated children to be highly exposed to heavy metals in dust via ingestion compared to adults. This study observed high pollution load of heavy metals in the studied areas and therefore appropriate measures need to be taken in order to manage the pollution
A thesis submitted to the Department of Chemistry, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the degree of Master of Philosophy in Chemistry.
Soil dust pollution, Human health risk,, Toxicity, Exposure, G