Assessing Levels of Lead Contamination in Soil and Predicting Pediatric Blood Lead Levels in Tema, Ghana

Ghana, in West Africa, has a long history of lead use. Leaded petrol was in use till 2004, while used and new lead-acid batteries are still common imports. Numerous lead-acid battery recycling factories dot the country. Tema, Ghana’s largest seaport and a major center for industrial activity, is among the nation’s suspected hot spots for lead contamination. Despite this, there is currently not enough data to Background. Tema, Ghana’s main industrial city, has many areas that are suspected to be contaminated by lead. Elevated lead levels can affect, among many other issues, mental development, kidney function and blood chemistry. Children are particularly at risk. Objectives. The objective of this study was to determine the concentration of lead in soil from selected sites in Tema and how these levels relate to local pediatric blood lead predictions. Methods. A total of 47 surface soil samples were taken from 9 different sites. Energy dispersive X-ray technique was employed to determine the levels of lead. Pediatric blood lead levels were estimated using the Integrated Exposure Uptake Bio-Kinetic Model For Lead in Children, developed by the U.S. EPA. Results. The study revealed that the selected sites are highly contaminated by lead. In particular, the concentration of Pb in soil at a used lead acid battery recycling facility exceeded regulatory limits for industrial soil as set by the U.S. EPA. The model for predicting concentrations of lead in the blood of age-specific children showed extremely high probabilities of BLLs exceeding regulatory limits. Conclusions. Based on the results of soil testing, sites that were expected to reveal lead exposure positively demonstrated high levels of contamination, in some areas exceeding U.S. and other national regulatory limits. This information is expected to help authorities make informed clean-up decisions. Competing Interests. The authors declare no competing financial interests.


Introduction
Ghana, in West Africa, has a long history of lead use. Leaded petrol was in use till 2004, while used and new lead-acid batteries are still common imports. Numerous lead-acid battery recycling factories dot the country. Tema, Ghana's largest seaport and a major center for industrial activity, is among the nation's suspected hot spots for lead contamination. Despite this, there is currently not enough data to adequately map out lead-contaminated sites for authorities to draw up appropriate clean-up plans. In fact, Ghana does not yet have safe blood lead reference levels to help guide these decisions.
The purpose of this study was, therefore, to ascertain the level of lead concentrations from potentially contaminated sites in the Tema municipality and to predict BLLs for children residing in or near these areas. Children are particularly at risk from lead because of the increased sensitivity of young tissues and organs to the heavy metal.
According to the WHO, blood lead concentrations between 12 µg/dL and 120 µg/dL in children can result in lower IQ, shorter attention span, learning disabilities, hyperactivity, impaired physical growth and motor skills development, as well as affect audio-visual abilities. Acute symptoms of lead poisoning include kidney dysfunction, anemia and brain damage. The risk of encephalopathy is raised at blood concentrations above 70 µg/dL. The risk for death from lead poisoning is very high in children with blood lead levels ≥ 150 µg/dL who do not receive medical treatment. 1 Due to this, lead contamination and exposure has been one of the most studied pollution-related phenomena over the past few decades. Lead contamination has been found in gasoline, paint, air, water, interior dust, soil and food. It can also be absorbed through the skin if people come into direct contact with contaminated soil and from drinking water when soluble forms are present in surface or groundwater. 5

Materials and Methods
Several predictive models for assessing human exposure to lead have been developed over the past few decades. 7-11 The Integrated Exposure Uptake Biokinetic Model for Lead in Children-Windows version (IEUBKwin) was used to predict the pediatric blood lead levels (BLL) in this work. The model utilizes 4 inter-related modules (exposure, uptake, biokinetic, and probability distribution) to estimate blood lead levels in children exposed to leadcontaminated media.
IEUBKwin allows the user to estimate levels for a hypothetical child or population of children. The geometric mean BLL is predicted from available information about the child's or children's exposure to lead. From this distribution, the model estimates the risk (i.e., probability) that a child or a population of children will have their BLL concentrations exceed a certain level of concern (typically 10 μg/dl). 5 Although the IEUBKwin has been used in several countries to estimate pediatric blood levels, no such study has been undertaken in Ghana. [12][13][14] As stated previously, Ghana does not currently have safe reference levels for pediatric blood lead; a generic value of 10 μg/dl was used for comparison.
A total of 9 sampling sites were selected. These included: 2 steel processing plants in a heavy industrialuse area; a used-lead acid battery (ULAB) recycling plant; mechanic workshops in a residential community; a waste-oil recycling plant at a light industrial-use area; a municipal waste disposal site which accepts both industrial and domestic waste; a municipal playground; a school park in a residential area; and the Ashaiman Fitter Line, which comprises residential facilities, schools, auto workshops and scrap yards. Currently, there are no known lead poisoning episodes that can be traced directly to the sites under study.
The sampling sites are shown in Figure 1.
The 47 top surface soil samples were collected using previously cleaned plastic spoons from the 9 sampling locations. The samples were collected and kept in separate pre-cleaned and labeled Ziploc polythene bags that were then sent to a laboratory for analysis. The samples were air-dried and sieved using 200 µm-sized mesh, then pulverized. Of the pulverised samples, 10 g were made into thick pellets of 2.5 cm in diameter using a hydraulic press with an applied load of 10 metric tons. 15 The total lead concentrations were determined using energy dispersive X-ray fluorescence (EDXRF) with a secondary target arrangement. EDXRF provides a rapid and nondestructive method for the analysis of trace and major elements in the samples. 16,17 The Compact 3K5 X-ray Generator EDXRF Spectrometer which was used for the elemental analysis had a molybdenum anode and operated at 800W (40kV and 20mA). The irradiation was done using a molybdenum secondary target arrangement coupled to a Peltier-cooled silicon drift detector (SDD) with a 12.5 µm beryllium window thickness. The SDD has a resolution of 136 eV for 5.9 KeV x-ray energy. Sample pellets were placed at an angle of 45° to the primary beam and irradiated for 600 seconds. IAEA Soil 7 Standard reference material was used for the validation of the analytical procedure. The EDXRF Ka line intensities were measured for all

Results and Discussion
The study was designed as a routine Aboh et al Within the vicinities of the sampling area, children were most often found either playing or engaged in some form of social activities, increasing the chances of exposure to lead. At the waste dump site, where a concentration of 715.7 mg/kg was recorded, children as young as 2 years old-the offspring of scavengerscould be found, sometimes even engaged in the activity of their parents.
It is based on the above that the IEUBKwin was used to predict the BLL for children between the ages of 0.5 to 7 years. The models conservatively assume that soil dust is the only means by which children come in contact with lead. This assumption makes it easy to determine BLL due to soil dust and effectively plan mitigation measures. 17 The result of the IEUBKwin model analysis is shown in Table 2.

Conclusion
This study demonstrated that all the sampled sites showed some levels of lead contamination. Areas found with significantly elevated levels are TS, SS, LI 9, AFL and GVTA, all having levels above the limits set by the Dutch list. The lead concentration in the soil at GVTA is also seen to exceed the regulatory limits for industrial soil as set by the U.S. EPA. The IEUBKwin model for predicting the concentration of lead in the blood of age-specific children showed very high probability of BLLs exceeding the regulatory limits in both children and adults at some of the sites. GVTA, which is a leadacid battery recycling site, recorded the highest contamination levels with BLL concentration of over 300 µg/ dl for all age groups with 99% chance of exceedances. It is recommended that any plans to remediate the contaminated sites should take into consideration the pediatric BLL and the protection of infants and children to reduce child morbidity and mortality.
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