Browsing by Author "Ikenaka, Yoshinori"
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- ItemCharacterization, Spatial Variation and Risk Assessment of Heavy Metals and a Metalloid in Surface Soils in Obuasi, Ghana(Black Smith Institute, 2018-08) Akoto, Osei; Bortey-Sam, Nesta; Nakayama, Shouta M.M.; Ikenaka, Yoshinori; Baidoo, Elvis; et. alSoil contamination with heavy metals and metalloids has become an increasingly important issue in recent years. Objectives. The present study examines possible contamination of the environment with metals from gold mining activities in Obuasi, Ghana. Methods. Soil samples were collected from commercial and residential areas and tailing dams in Obuasi in order to investigate the extent of lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu), zinc (Zn), cobalt (Co), chromium (Cr), nickel (Ni) and arsenic (As) pollution, create thematic maps showing the extent of heavy metals pollution, identify the sources of pollution, and to assess risks to humans and the surrounding ecological system. Results. Mean concentrations of metals from the study were found in the order of As > Cu > Zn > Cr > Ni > Pb > Co > Hg > Cd. The results showed that all communities were severely polluted with As, and distribution maps highlighted two hot spots at the sulfite treatment plant and Pompura treatment plant tailings dams. Additionally, the levels of Pb, Cu and Zn were elevated around the city center where vehicular traffic is very dense. Principal component analysis indicated that mining activities may have significantly contributed to metal levels in Obuasi soils. The potential ecological risk (RI) indicated that soils in 41% of the communities pose very high risks to the surrounding ecological system, 50% pose considerable risk, and 9% pose a moderate risk. Arsenic and Hg contributed 73 and 15% of the RI, respectively. The average hazard quotient due to soil As exposure was 2.51 ± 1.23 and ingestion of soils in 95% of the communities in the study area could pose non-carcinogenic health risks to children. Moreover, the average cancer risk for children from the communities was 1.13 × 10-3. Based on the United States Environmental Protection Agency (USEPA) recommendation for cancer risk of 10-6 to 10-4, the cancer risk for children (> 10-3) was higher in 45% of the studied communities. Conclusions. The central part of the study area is polluted with Pb, Zn and Cu, and As pollution is severe in all of the studied communities. The RI from all study sites revealed very high risk to the ecological system, including mammals. There could be non-cancer and cancer risks to Obuasi residents due to ingestion of As-contaminated soils, and children are particularly vulnerable. Competing Interests. The author declares no competing financial interests
- ItemContamination Levels and Sources of Heavy Metals and a Metalloid in Surface Soils in the Kumasi Metropolis, Ghana(Black Smith Institute, 2017-09) Akoto, Osei; Bortey-Sam, Nesta; Ikenaka, Yoshinori; Nakayama, Shouta M.M.; Baidoo, Elvis; et. alEnvironmental contamination with heavy metals and metalloids due to industrial, smelting and mining activities have become common in large and growing cities. Kumasi is one of the most industrialized cities in Ghana and experiences metal pollution due to recent and past activities. Although metals are naturally abundant in the area, their accumulation in soils could potentially lead to adverse effects on local ecosystems. Objectives. The aims of this study were to determine the distribution, enrichment, geo-accumulation and sources of metals in Kumasi soils and to estimate the contamination factor (CF) and pollution load index (PLI) of these metals in soils. Methods. Concentrations of eight heavy metals and a metalloid were determined in 112 soil samples randomly collected from 31 sampling sites in the area. In addition, 5 soil samples were collected from a pristine site (Kwame Nkrumah University of Science and Technology Botanical Gardens) for data comparison, to determine the local background values for metal concentrations and to evaluate the extent of metal pollution in the study area. Results. Heavy metals such as zinc (Zn), lead (Pb), cadmium (Cd) and chromium (Cr) were enriched in 65, 32, 58 and 93% of the sampling sites, respectively, and geo-accumulation indexes for Cr, Zn, Cd, mercury (Hg) and Pb showed moderate to extreme contamination in 100, 97, 77, 65 and 45% of the sampling sites, respectively. Principal component and cluster analyses revealed that industrial activities including mining were the major sources of metals in Kumasi soils with high metal input in the community of Suame. Distribution maps revealed hotspots of Cd, nickel (Ni), arsenic (As), cobalt (Co), copper (Cu) and Pb in Suame. The highest CFs for Cu, Cd, Ni, As, Co and Pb highlighted anthropogenic inputs in Suame, while Hg was highest in Mbrom, Zn in Suntreso, and Cr in Aboabo. Conclusions. The PLI of metals revealed Suame as the most polluted study site, while Anomangye and Bomso were the least polluted. Competing Interests. The authors declare no competing financial interests.
- ItemDistribution of Heavy Metals in Organs of Sheep and Goat Reared in Obuasi: A Gold Mining Town in Ghana(International Journal of Environmental Science and Toxicology, 2014) Akoto, Osei; Bortey-Sam, Nesta; Nakayama, Shouta M.M.; Ikenaka, Yoshinori; Elvis Baidoo; et. alThe aim of this study was to determine the concentration of metals in some organs of goat and sheep and assess the distribution of these metals in the sample tissues. Samples were digested with 60% nitric acid and concentrations of the heavy metals measured using atomic absorption spectrophotometer while the concentrations of Hg were measured with mercury analyzer. Concentrations of Zn, Cu were very high in the organs followed by Cr, Ni, Co, Pb, Cd, As and Hg. Total rank score assessment showed that liver, kidney and lung had accumulated high levels of metals while brain accumulated lowest. Mean Zn concentrations in all organs ranged between 24.88±11.22 in goat brain and 97.06±19.66 mg/kg in liver of goat. Mean Cu concentrations ranged between 7.96±1.20 (small intestine of sheep) and 106.63±111.24 mg/kg in liver of sheep. Cd concentration in liver and kidney in both species were above the EU set limit of 0.05 mg/kg. Concentrations of Co in liver, kidney and lungs of the two different animals did not vary significantly. As and Hg concentration were homogenous in all the organs of both animals and did not show any significant variation. Prolonged consumption of kidney, liver and lungs of goats and sheep having high concentrations of Zn Cu and Cd may lead to accumulation of these metals in humans and cause metal toxicity.
- ItemExcretion of polycyclic aromatic hydrocarbon metabolites (OH-PAHs) in cattle urine in Ghana(Elsevier, 2016-11-01) Bortey-Sam, Nesta; Ikenaka, Yoshinori; Akoto, Osei; Nakayama, Shouta M.M.; Marfo, Jemima; et. alPrevious studies of polycyclic aromatic hydrocarbons (PAHs) in particulate matter, soils and livers of wild rats indicated that the city centre of Kumasi, Ghana has been severely polluted with high cancer potency. Cattle urine were therefore collected from Kumasi (urban) and Offinso (rural), Ghana: to determine concentrations of urinary PAH metabolites (OH-PAHs); and find their association with sex; and to estimate exposure of cattle to PAHs from the different sites. From the results, geometric mean concentrations (adjusted by specific gravity), GMSG, showed that 2-OHNaphthalene (2-OHNap) was the most abundant OH-PAH in cattle urine from all study sites, and naphthalene-containing-mothballs might have contributed significantly to the levels. There was no significant difference between urinary OH-PAHs concentrations in cattle from urban and rural sites except for 2-OHPhe and 4-OHPhe, and similar to urban areas, rural sites could also be polluted with PAHs. GMSG of 2-OHNap in cattle urine in Kokote (21.9 ± 6.51 ng/mL; a rural area), was significantly higher compared to the other sites followed by Oforikrom (4.15 ± 4.37 ng/mL; urban). The GMSG concentration (ng/mL) of the sum of OH-PAHs decreased in the order, Kokote (44.7) > Oforikrom (7.87) > Saboa (6.98) > Santasi (6.68) > and Twumasen Estate (5.23). The high concentrations of urinary 2-OHNap, 2-3-OHFlu, 2-OHPhe, 3-OHPhe and 4-OHPhe in Kokote indicated high PAHs exposure to cattle in this area or different/specific source of PAHs exposure. GMSG of 2-OHNap was significantly higher in male cattle compared to females while 1-9-OHPhe was significantly higher in females. Capsule: 3 PAH metabolites were measured in cattle urine in urban and rural areas in Ghana; 2- OHNaphthalene (2-OHNap) was the most abundant PAH metabolites.
- ItemExposure levels of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in wild rats in Kumasi, Ghana(Peer reviewed and revised papers, 2015-08-31) Bortey-Sam, Nesta; Ikenaka, Yoshinori; Akoto, Osei; Nakayama, Shouta M.M.; Yohannes, Yared Beyene; et. alWild rats were trapped from communities in Kumasi, Ghana, to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) and heavy metals. The results of the study showed that phenanthrene (0.51 ± 0.08 ng/g dw) was the most abundant individual PAH in the liver of wild rats. The ΣPAH concentrations in liver ranged from 0.05 to 1.64 ng/g dw in Bomso (a community) and city centre, respectively. Abundance of individual PAHs in the liver of wild rats decreased in the order: phenanthrene > pyrene > acenaphthene > naphthalene > fluoranthene and > anthracene. Levels of phenanthrene and pyrene detected were significantly higher than other PAHs. Naphthalene and fluoranthene were detected in 80% and 78% of the samples collected respectively. Heavy metals in the liver of wild rats in Kumasi decreased in the order Zn > Cu > As > Ni > Pb > Co > Cd > Cr.
- ItemHuman health risks from metals and metalloid via consumption of food animals near Gold Mines in Tarkwa, Ghana: Estimation of the daily intakes and target hazard quotients (THQs)(Academic Press, 2015-01-01) Bortey-Sam, Nesta; Nakayama, Shouta M.M.; Ikenaka, Yoshinori; Akoto, Osei; Baidoo, Elvis; et. alHeavy metal and metalloid contamination in food resulting from mining is of major concern due to the potential risk involved. Food consumption is the most likely route for human exposure to metals. This study was therefore to estimate the daily intake and health risk (based on target hazard quotients, THQ) from metals via consumption of free-range chicken, goat and sheep near gold mines in Tarkwa, Ghana. The concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb were measured with an inductively coupled plasma33 mass spectrometer and Hg analysis was done using the mercury analyzer. The mean concentrations of metals ranged from nd–542 mg/kg wet weight. Principal component analysis of the results showed a clear separation between chicken, grouped on one side, and the ruminants clustered on another side in both offal and muscle. Interestingly, As, Cd, Hg, Mn and Pb made one cluster in the offal of chicken. Chicken muscle also showed similar distribution with As, Hg and Pb clustered together. The daily intake of As (μg/kg body weight/day) were in the following ranges; [0.002 (kidneys of goat and sheep)–0.19 (chicken gizzard)], Cd [0.003 (chicken muscle)–0.55 (chicken liver)], Hg [0.002 (goat muscle)–0.29 (chicken liver)], Pb [0.01 (muscles and kidneys of goat and sheep)–0.96 (chicken gizzard)] and Mn [0.13 (goat kidney)–8.92 (sheep liver)]. From the results, daily intake of As, Cd, Hg, Pb and Mn in these food animals were low compared to the provisional tolerable daily intake guidelines. The THQs although less than one, indicated that contributions of chicken gizzard and liver to toxic metal exposure in adults and especially children could be significant.