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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Date
May, 2019
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Abstract
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
Description
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.
Keywords
Soil dust pollution, Human health risk,, Toxicity, Exposure, G