Human health risk assessment of potentially toxic elements in soil and air particulate matter of automobile hub environments in Kumasi, Ghana

Rapid urbanization and uncontrolled industrial activities in developing countries have raised concerns about potentially toxic metal contamination of the environment. This study assessed the levels of potentially toxic elements in soil and airborne particulate matter in the Suame and Asafo areas in the Kumasi metropolis, characterized by a high concentration of auto mechanic workshops and residential settlements. X-ray fluorescence analysis and inductively coupled plasma-mass spectrometry were used to determine the metal concentrations in the samples. The results showed high concentrations of potentially toxic elements in the soil and air samples, indicating contamination from automotive activities. Metals such as Co, Ni, Pb, and Zn were found to be present at concentrations (13.42-6101.58 mg/kg and 14.15-11.74 mg/kg for Suame and Asafo respectively) that pose potential health risks to exposed populations. Mathematical models such as pollution indices were used to assess the extent of contamination and determine the potential sources of the metals - the automotive repairs. The findings highlight the urgent need for environmental management and remediation strategies to mitigate the health risks of exposure to potentially toxic elements in the Kumasi metropolis automotive hub.

Human exposure to mercury in the atmosphere and soils in Konongo: an age-old mining centre in the Ashanti Region of Ghana

The dramatic upsurge of artisanal and small-scale gold mining (ASGM) activities in Ghana has resulted in environmental degradation, water pollution and human exposure to mercury-the main hazardous element used in gold extraction. This study evaluated the degree of human exposure to mercury based on the concentrations found in the air and soil samples taken at a resolution of 1 km² across Konongo, a historic mining town in Ghana's Ashanti Region. The highest atmospheric mercury concentration was 193 ng/m³, which is much higher than the levels the European Union and Japan allowed, which are 10 ng/m³ and 40 ng/m³, respectively. The concentration in the soil was 3.6 mg Hg/kg, which is around ten times higher than the background concentration in nature. Additionally, the soil concentrations were higher above the worrisome levels of soil contamination in agricultural land (4 mg/kg) and industrial areas (16 mg/kg), respectively. Soils are extremely contaminated with mercury at sites artisanal mining activities take place. The concentrations of mercury in the air and soils were significantly higher (p < 0.5) at locations of prominent mining activities compared to areas not close to mining sites. The inhabitants of the Konongo community are therefore exposed to mercury, most likely emitted from artisanal mining activities. A non-carcinogenic risk is posed to the people by inhaling mercury vapour through the air and vapourisation from the soil. Children are exposed to a higher risk than adults as they receive higher daily doses of mercury than adults.

Modelling mercury concentration in Ghanaian soil

Mercury usage in Artisanal Small Scale Gold Mining is a major anthropogenic source of mercury in the environment. In this study, mercury pools and fluxes have been established for Ghana, which has a large ASGM sector, based on estimated losses of mercury to the environment, deposition calculated with GLEMOS, a global long-range transport model for mercury in air, and mercury measured in soils and water in Ghana. A model for mercury in soils and water of Ghana with a resolution of 5 × 5 km² and a monthly or yearly time step has been developed to assess the regional increase in soil and water concentrations that can be attributed to anthropogenic sources and to simulate scenarios into the future. The model has been calibrated to reproduce present-day mercury concentration in the soil (average 0.0193 mg kg^-1) with current deposition calculated with the long-range transport model and past years' deposition based on a scenario for the historic development of the mining activity. This calculation gives an average increase in soil concentrations from anthropogenic sources of 22%. The model gives a fair description of the regional differences in soil concentrations but underestimates concentrations in regions with intense mining activity and overestimates concentrations in regions with less mining when using deposition from the long-range model as input.

Characterization of inhalation exposure to gaseous elemental mercury during artisanal gold mining and e-waste recycling through combined stationary and personal passive sampling

While occupational inhalation exposure to gaseous elemental mercury (GEM) has decreased in many workplaces as mercury is being removed from most products and processes, it continues to be a concern for those engaged in artisanal and small-scale gold mining or in recycling mercury-containing products. Recently, stationary and personal passive air samplers based on activated carbon sorbents and radial diffusive barriers have been shown to be suitable for measuring GEM concentrations across the range relevant for chronic health effects. Here, we used a combination of stationary and personal passive samplers to characterize the inhalation exposure to GEM of individuals living and working in two Ghanaian gold mining communities and working at a Norwegian e-waste recycling facility. Exposure concentrations ranging from <7 ng m^-3 to >500 μg m^-3 were observed, with the higher end of the range occurring in one gold mining community. Large differences in the GEM exposure averaged over the length of a workday between individuals can be rationalized by their activity and proximity to mercury sources. In each of the three settings, the measured exposure of the highest exposed individuals exceeded the highest concentration recorded with a stationary sampler, presumably because those individuals were engaged in an activity that generated or involved GEM vapors. High day-to-day variability in exposure for those who participated on more than one day, suggests the need for sampling over multiple days for reliable exposure characterization. Overall, a combination of personal and stationary passive sampling is a cost-effective approach that cannot only provide information on exposure levels relative to regulatory thresholds, but also can identify emission hotspots and therefore guide mitigation measures.

Contamination, exposure and risk assessment of mercury in the soils of an artisanal gold mining community in Ghana

Mercury pollution has pervaded many artisanal gold mining communities in the world, especially in developing countries. This study aimed to evaluate the potential risk of mercury pollution in soils in Gbani, an artisanal gold mining community in Ghana. Two hundred and thirty-seven soil samples were collected from within 0-10 cm depth, from active mining sites near residences, two transects in the community, waste soil from mining processing and the surroundings of the community. The measured mean mercury soil concentrations were 71 mg Hg/kg in active mining sites, and more moderate (2.7 mg Hg/kg) along transects through the community. Enrichment Factors classified the soils of the study area as being moderately to extremely severely contaminated with mercury. The spatial distribution shows the contamination of mercury is highest at residential facilities and decreases through the community to the outskirts covered by vegetation. Hazard quotients for non-cancer effects identified air-borne exposure pathways for humans to pose the largest risk, including the inhalation of vapour. The average hazard indices recorded were 0.5 (child) and 0.1 (adult) at the grid, 2 (child) and 0.3 (adult) at the transects, 1.6 (child) and 0.2 (adult) for waste soil and 76 (child) and 10.9 (adult) at the mining sites. The inhabitants of Gbani community are therefore at risk of non-cancer effects of mercury as the hazard quotients and hazard index were above one.

Human health risk assessment of exposure to indoor mercury vapour in a Ghanaian artisanal small-scale gold mining community

People living or working in and around artisanal small-scale gold mining communities can be exposed to mercury vapour, which may negatively affect their health. In this study, the human exposure to air borne mercury in an artisanal mining community in the Upper East region of Ghana was investigated using Lumex RA 915 M mercury analyser, an active sampler. The concentration of mercury in air was measured inside and outside households and was related to human health risk standards. For each household, one measurement was taken from outside and three from inside at different positions. About 91% of the households where amalgam burning was reported had concentrations higher than the USEPA reference dose of 300 ng m^-3 whereas 64% of the households where amalgam burning was not reported exceeded the reference dose above. The maximal (upper) instrumental limit (50,000 ng m^-3) was passed for the highest concentrations, so, the upper 97.5% concentration was estimated, using censored statistics, to exceed 800,000 ng m^-3 for the fireplaces. This exceeds any reported indoor household air concentration of Hg, identified by the literature review in this paper. Estimated hazard quotients were found to range from <1 to 108 within the households that are reported not to burn amalgam. In the households where amalgam burning reportedly takes place, the hazard quotient had a range of 0.01-160. Mercury concentrations measured in households with reported amalgam burning are approximately ten times higher than those households with no reported burning of amalgam. The censored data predicted hazard quotients up to 966. The results indicate that both miners and non-miners of the community are at risk of adverse health effects resulting from inhalation of mercury vapour.

Human Health Risk and Bioaccessibility of Toxic Metals in Topsoils from Gbani Mining Community in Ghana

BACKGROUND

Anthropogenic activities such as artisanal mining pose a major environmental health concern due to the potential for discharge of toxic metals into the environment.

OBJECTIVES

To determine the distribution and pollution patterns of arsenic (As), iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), manganese (Mn), copper (Cu) and zinc (Zn) in the topsoil of a mining community in Ghana, along with potential human health risks and in vitro bioaccessibility.

METHODS

Concentrations of metals were determined using X-ray fluorescence techniques and validated using inductively coupled plasma-mass spectrometry.

RESULTS

Concentrations of the metals in topsoil were in the order of magnitude of Cu (31.38 mg/kg) < Ni (45.39 mg/kg) < As (59.66 mg/kg) < Cr (92.87 mg/kg) < Zn (106.98 mg/kg) < Mn (1195.49 mg/kg) < Fe (30061.02 mg/kg). Geo-statistical and multivariate analyses based on hazard indices including contamination, ecological risks, geo-accumulation, and pollution load suggest that the topsoils are contaminated in the study area. The potential ecological risk index (PERI) showed high ecological risk effects (PERI=269.09), whereas the hazard index (1×10-7) and carcinogenic risk index (1×10-5) indicated low human health risks. Elevated levels of As, Cr, Ni, and Zn were found to emanate from anthropogenic origins, whereas Fe, Mn, and Cu levels were attributed mainly to geological and atmospheric depositions. Physicochemical parameters (pH, electrical conductivity and total organic carbon) showed weak positive correlations to the metal concentrations. Elemental bioaccessibility was variable, decreasing in the order of Mn (35± 2.9%) > Cu (29± 2.6%) > Ni (22± 1.3%) > As (9± 0.5%) > Cr (4± 0.6%) > Fe (2± 0.4%).

CONCLUSIONS

Incorporation of in-vitro bioaccessibility into the risk characterization models resulted in a hazard index of less than 1, implying low human health risks. However, due to accumulation effects of the metals, regular monitoring is required.

COMPETING INTERESTS

The authors declare no competing financial interests.

Distribution and bioaccessibility of metals in urban soils of Kumasi, Ghana

To assess the potential risk associated with incidental ingestion of metal contaminants in soils from areas where most of the commercial activities are concentrated in Kumasi, Ghana, total and bioaccessible concentrations of metals were determined in surface soil samples. Arsenic, Cr, Cu, Pb, and Zn in some of the samples exceeded international environmental soil quality guidelines. The use of geoaccumulation and enrichment factor indices also indicated high contamination in select areas of the commercial hub. Multivariate analyses of the data suggested that As, Cr, Cu, Ni, Pb, and Zn were mainly derived from anthropogenic sources whereas Al, Cd, Hg, and Fe were attributable to either soil parent materials or atmospheric deposition. Based on the total metal concentrations, the risk associated with exposure to metals in the contaminated soils was found to be high; the hazard quotient based on the mean concentration for a child receptor was greater than 1 for As, Cr, and Pb. Metal bioaccessibility was variable; decreasing in the order Zn (73 ± 15%) > Pb (62 ± 16%) > Cu (47 ± 14%) > Co (28 ± 11%) > Ni (24 ± 11%) > As (14 ± 13%) > Cr (2.8 ± 2.6%). Incorporation of the bioaccessibility data in the risk characterization resulted in hazard quotients of less than 1 indicating that the general risk associated with incidental ingestion of metals in the soils for both children and adults is low except for the contaminated hotspots. Lead and As contributed most to the overall risk.

Pregnancy-associated malaria in a rural community of ghana

OBJECTIVES

Pregnant women in malaria-endemic communities are susceptible to Plasmodium falciparum infections, with adverse consequences including maternal anaemia, placental malaria parasitaemia and infant low birth weight (LBW). We sought to assess the prevalence, incidence, and clinical markers of pregnancy-associated malaria (PAM) in a rural district of Ghana.

METHODS

A total of 294 pregnant women were enrolled and followed passively and actively, monthly and weekly until delivery. Haemoglobin levels, malaria parasitaemia and Hb electrophoresis were done from peripheral blood samples. At delivery, placental smears were examined for malaria parasites.

RESULTS

Prevalence of peripheral blood P. falciparum parasitaemia at enrolment was 19.7% and related to parity. Incidence rate of parasitaemia was 0.06 infections/ person/month [95% confidence interval (CI): 0.04 to 0.08]. Symptomatic infections rose sharply from the first trimester to the last. Prevalence of malaria parasites in the placenta was 35.9% (61/170) and highest among primigravidae (P(chi(2))=0.006). Incidence of LBW infants was 17.7% (30/170), most common among those with placental P. falciparum infection (P(chi(2))=0.005) corresponding to a relative risk of 2.8 [1.4 to 5.2]. Median infant birth weight in those with placental infection was significantly lower than in those without infections (P(chi(2))=0.001). Maternal haemoglobin levels were lower (9.7 [9.3-10.1] g/dL) at enrolment, among women who subsequently had placental P. falciparum infection than among those who did not have placental infection at delivery (10.5 [10.2-10.8] g/dL) (P (t)=0.003).

CONCLUSION

Primigravidae and secundigravidae are significantly at risk of developing PAM, and low haemoglobin during pregnancy is a clinical indicator of placental P. falciparum infection.