Health risk assessment of lead exposure to children in Blantyre, Malawi

Utembe, Wells Robert
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Although lead (Pb) is highly toxic, exposure to Pb has not been studied in Malawi. The aims of this study were therefore to: 1. Determine the levels of Pb from different sources of exposure such as food, water, and soil/house dust to predict the levels of Pb in blood (BPb) using the Integrated Exposure Uptake Biokinetic (IEUBK) model. 2. Measure the levels of BPb and compare to those predicted from the IEUBK model as an indication for its applicability in Malawi. 3. To relate the measured and predicted BPb levels as well as the prevalence of high BPb to potential health effects using the WHO and CDC guidelines. 4. Assess burden of disease using WHO spreadsheets. 5. Identify additional sources and risk factors for exposure to Pb in children in Malawi to assist the policy makers to reduce exposure to lead. In this cross-sectional study 152 children, aged 1-6 years, were recruited. To determine sources of exposure, children’s toys, domestic paints, foods, house dust, playground soil and water were collected and analyzed for Pb. A Pb exposure risk assessment questionnaire was also administered to identify potential risk factors and a 7-day food frequency questionnaire was used to collect information on food consumption. For measured BPb levels, venous blood was collected and analysed. Logistic regression was performed in STATA to evaluate the relationship between risk factors and high BPb (BPb ≥ 5 μg/dl). The comparisons between predicted and measured blood lead showed that the IEUBK model may be used provided that the bioavailability values for lead from different sources are available as well as the food consumption rates are provided for Malawi.. There was also a high prevalence (71.7%) of high BPb that is expected to result in 8.38 cases of mild mental retardation per 1000 children aged less than five years. From the identified risk factors, only areas of residence has correlated to prevalence of high BPb in statistically significant manner (p = 0.013). It can therefore be concluded that IEUBK model may be used for Malawi, that a significant proportion of children in Blantyre are exposed to levels of lead that are detrimental to their health and that exposure to lead in Blantyre require urgent intervention measures.
A thesis submitted to the School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirement for the degree of Doctor of Philosophy Johannesburg, August 2016