Human Health Risk Assessment of Exposure to Heavy Metals in Selected Mining Communities in Ghana.
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Date
2018-01
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Publisher
University Of Ghana
Abstract
Gold mining is an important economic activity in Ghana. However, processing and extraction of gold from its ores generate a lot of wastes. Studies conducted in different countries have established that long-term exposure to As, Cd, Pb and Hg in the wastes could cause cancer and other non-cancerous diseases such as cardiovascular diseases. It is within this context that, this thesis assessed cancer and non-cancer human health risk associated with exposure to As, Cd, Hg and Pb in water and sediment via oral and dermal contact by receptors such as adults workers in mining companies or artisanal small-scale mines (ASM), resident adults (i.e., who do not work in either mining companies or ASM) and resident children in selected mining communities in Ghana. The study further evaluated the health risk associated with ingestion of food crops such as cassava grown in soils the study areas as well as the determination of levels of As, Cd, Pb and Hg in human such as whole blood and serum among resident adults (non-mine workers i.e., workers of mining companies or ASM), and resident children in selected mining and non-mining communities in Ghana in line with USEPA risk assessment guidelines as there exist limited information on this subject in Ghana.
The study protocol was approved by the Ghana Health Service Ethical Review Committee. Random sampling techniques were adopted in selecting the sampling sites as well as recruitment of respondents who donated their blood samples as well as provided information about their personal health in relation to cardiovascular diseases. The collected water, sediment and cassava samples were stored under 4ºC and conveyed to the CSIR-Water Research Institute laboratory
for analysis. The blood samples were collected by laboratory staff of Tarkwa Nsuaem Municipal Hospital, Cape Coast metropolitan Hospital, Health Centre at Bole and Nangodi respectively. The blood samples were separated into whole blood and serum by the laboratory staff and conveyed to Ghana Atomic Energy Commission for analysis of As, Cd and Hg using the NAA at Ghana Reactor 3 under -4ºC; while the Pb levels in the blood samples were determined using GFAAS at Heavy Metals Laboratory of CSIR-Water Research Institute.
The mean concentrations for As, Hg, Cd and Pb in whole blood of resident adults from mining communities in Tarkwa Nsuaem Municipality were; 38 ± 0.20 μgL-1, 63 ± 0.23 μgL-1, 303 ± 117 μgL-1 and 28 ± 14 μgL-1 respectively; while the levels of As, Hg, Cd and Pb measured in serum of resident adults from mining communities were; 65 ± 14 μgL-1, 358 ±22 μgL-1, 134 ± 12 μg/L, 58
±5.8 μgL-1 respectively for As, Hg, Cd and Pb. These were found to have exceeded the permissible WHO guideline values. The mean concentrations of As, Cd, Hg and Pb in water samples ranged from 15 μg/L to 325 μg/L (As), 0.17 μg/L to 340 μg/L (Cd), 0.17 μg/L to 122 μg/L (Pb) and 132 μg/L to 866 μg/L (Hg) respectively. These measured concentrations of arsenic (As), mercury (Hg), cadmium (Cd) and lead (Pb) were used as input parameters to calculate the cancer and non–cancer health risks from exposure to these metals in surface water bodies and sediments based on an occupational exposure scenario using Central Tendency Exposure (CTE) and Reasonable Maximum Exposure (RME) parameters. The results of the non-cancer human health risk assessment for small-scale miners working around river Anikoko were expressed in terms of hazard quotients based on CTE parameters are as follows: 0.04 (Cd), 1.45 (Pb), 4.60 (Hg) and 1.98 (As); while cancer health risk faced by ASGM miners in Dumase exposed to As in River Mansi via oral ingestion of water is 3.1 × 10−3. The hazard quotient results obtained from this study in most cases were above the HQ guidance value of 1.0. Furthermore the cancer health risk results were found to be higher than the USEPA guidance value of 1 × 10−4 to 1 × 10−6. The findings from case-control epidemiological studies established a strong relationship between exposure to As in drinking water and incidence of cardiovascular diseases among residents in the study areas. The results from this study calls for strong policy interventions to address the issue of health and safety of both mine workers and residents of mining communities in Ghana.
Description
PhD. Nuclear and Environmental Protection
Keywords
Health Risk Assessment, Heavy Metals, Mining, Ghana