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

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 2016Although 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.MT201

Radon exposure risks among residents proximal to gold mine tailings in Gauteng Province, South Africa: a cross-sectional preliminary study protocol

Gold mine tailings, a legacy of the mining industry, harbors significant amount of radon gas, a classified human carcinogen. Radon exposure, especially near tailings, is a significant public health threat, potentially leading to increased risk of lung cancer, leukemia, and chronic obstructive pulmonary disease (COPD). These health problems are often associated with lower survival rates and significant financial burdens. This ongoing research aim to evaluating the relationship between indoor radon exposure and lung cancer, leukemia, and COPD risks among residents proximal to gold mine tailings in Gauteng Province, South Africa. This cross-sectional preliminary study focus on two distinct groups: Riverlea (exposed group, <2 km to Gold mine tailings) and Orlando East (unexposed group, >2 km to Gold mine tailings). Indoor radon levels is measured using AlphaE monitors, while health risks (lung cancer, leukemia, and COPD) linked to exposure are evaluated through interview-administered questionnaire and secondary data from Gauteng Health Department. Of the 476 residents randomly selected for this study, 300 have already participated, with balanced representation from both the exposed and unexposed groups. The study will compare indoor radon levels and health outcomes between the two groups. This study’s results could aid in creating targeted interventions and policies to mitigate indoor radon exposure risks and safeguard vulnerable communities from this significant public health hazard

The Knowns and Unknowns of Chemically Induced Lower Respiratory Tract Microbiota Dysbiosis and Lung Disease

Exposure to chemicals in many occupational and environmental settings has the capacity to significantly disturb the commensal microbiota that symbiotically reside in humans. However, much more is known about gut microbiota (GM) than lung microbiota (LM) due to the challenges of collecting LM samples. The advent of culture-independent methodologies has revealed the complex and dynamic community of microbes harbored by the respiratory tract. It is now being recognized that LM can directly impact immunity in a manner that can result in disease. Significant differences in community composition and diversity have been shown between the LM of diseased lungs and those of healthy subjects. Studies have linked LM dysbiosis with human diseases such as idiopathic pulmonary fibrosis, lung inflammation, chronic obstructive pulmonary disease (COPD), asthma, and lung cancer. However, it is not known whether LM dysbiosis initiates/promotes disease pathogenesis or is merely a biomarker of disease. Many chronic lung diseases often occur together with chronic GIT diseases in what is termed as the gut–lung axis. The LM also affects the CNS, in the bidirectional lung–brain axis, through a number of potential mechanisms that include the direct translocation of micro-organisms. Chemically induced LM dysbiosis appears to play a significant part in human diseases as has been shown to arise due to air pollution, cigarette smoking, and the use of chemical antibiotics

Issues and Challenges in the Application of the IEUBK Model in the Health Risk Assessment of Lead: A Case Study from Blantyre Malawi

The risk assessment of lead (Pb) requires the use of biokinetic models to translate measured concentrations of Pb in food and environmental media into blood lead (BPb). The aim of this study was to assess the applicability of the Integrated Exposure Uptake Biokinetic (IEUBK) model in the health risk assessment of Pb among children in Blantyre. Children (152) aged 1–6 years were recruited into this cross-sectional study, and foods, house dust, playground soil, water, and venous blood (1 mL) were collected and analyzed for Pb. A seven-day food frequency questionnaire (FFQ) was used to collect food consumption data. The concentrations of Pb ranged from 0.01 to 3.3 mg/kg in food, 2.3 to 265 mg/kg and 1.5 to 482 mg/kg in house dust and playground soil, respectively, as well as 2.0 µg/dL to 50.4 µg/dL and 6.8 to 39.2 µg/dL for measured and predicted BPb, respectively. Various statistical tests indicated less than satisfactory agreement between measured and predicted BPb values. Despite the lack of reliable food consumption data and other limitations, both the predicted and measured BPb values indicate that children in Blantyre are exposed to high levels of Pb, largely through food and soil as a minor source

Lung Dosimetry Modelling in Nanotoxicology: A Critical Analysis of the State of the Art

The estimation of the dose of inhaled nanomaterials is of fundamental importance in occupational and environmental health. Indeed, the toxicology and risk assessment of inhaled NMs depends on deposition rates in various parts of the lung, coupled with clearance/retention rates that depend on processes such as physical removal by ciliary clearance, macrophage-mediated clearance and lymphatic clearance, together with dissolution and disintegration. A number of lung dosimetry models have been designed to estimate the deposition and retention of inhaled particles, including empirical models, deterministic models, stochastic statistical models and mechanistic multiple-path models. Various assumptions are used in these models, including use of a symmetrical or asymmetrical lung, which affects the performance of these models. This study presents the most recent developments of in vivo dosimetry in nanotoxicology, with a focus on the design and modelling approach, and the required input data used, together with verification and validation status of the model. Widely implemented models in nanotoxicology were identified and analyzed, i.e., the Multiple Path Particle Dosimetry (MPPD) model, International Commission on Radiological Protection (ICRP) models, the National Council on Radiation Protection and Measurement (NCRP) model, the Exposure Dose Model (ExDoM) and the Integrated Exposure and Dose Modeling and Analysis System (EDMAS)

Occupational and Environmental Chemical Risk Assessment in a Changing Climate: A Critical Analysis of the Current Discourse and Future Perspectives

Global climate change (GCC) models predict direct changes in region-specific rainfall patterns, floods, sea levels, infectious and heat-related disease patterns. The indirect effects of GCC on chemical risk assessment (CRA) have not received adequate attention. This study presents a synopsis of the implications of GCC on CRA, which forms the basis for both occupational and environmental health. GCC can make organisms more sensitive to chemical stressors, and chemical exposures can make organisms more sensitive to GCC. Consequently, occupational and environmental chemical RA will need mechanistic understanding and analytical tools to predict outcomes of multiple stressors and their combined effects

Study Protocol to Determine Association between Environmental Triggers and Asthma among Children in King Williams Town

Asthma affects over 330 million people worldwide, with relatively higher disease burdens in Australia, New Zealand, Africa, the Middle East, and South America. The symptoms associated with asthma were reported to be prevalent in children from the period of 1993 to 2013, in many low- and middle-income countries, due to changes in environmental conditions, such as domestic lifestyle, and urban and industrial developments. (1) Background: Several studies have also shown that children are prone to a severe type of asthma, because of their narrow respiratory airways and susceptibility to irritation from environmental agents. This study aimed to assess the association between environmental exposure and asthma among children in King Williams Town, South Africa. (2) Methodology: This study adopted a cross-sectional design method, with an estimated sample size of 262 participants. The eligible study participants were enrolled while attending Grey hospital in King Williams Town, for asthma management. Information will be collected from eligible, stable participants, on asthma treatment, through in-person interviewing in 2021. A semi-structured questionnaire will be administered to the participants. However, as a result of the prevailing COVID-19 pandemic, data may be abstracted from the asthma medical record of the eligible participants. Multivariate regression will be utilized, to describe the correlation between the variables, and the odds ratio will be calculated as well. (3) Discussion and conclusion: The study will objectively identify the local environmental agents that are associated with asthma among children in King Williams Town, in order to reprioritize treatment and preventative strategies. Ethical approval was obtained from the Research Ethics Committee, Faculty of Health Sciences at the University of Johannesburg

A Review of Metal Levels in Urban Dust, Their Methods of Determination, and Risk Assessment

This review gives insights into the levels of metals in urban dust, their determination methods, and risk assessment. Urban dust harbors a number of pollutants, including heavy metals. There are various methods used for the sampling of urban dust for heavy-metal analysis and source-apportionment purposes, with the predominant one being the use of plastic sampling materials to avoid prior contamination. There are also various methods for the determination of metals, which include: atomic absorption spectroscopy (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS), among others. Studies have shown that pollutants in urban dust are mainly derived from industrial activities and coal combustion, whereas traffic emissions are also an important, but not a predominant source of pollution. The varying particle-size distribution of urban dust and its large surface area makes it easier for the deposition and transport of heavy metals. Risk-assessment studies have shown that metals in urban dust could cause such problems as human pulmonary toxicity and reduction of invertebrate populations. The risk levels seem to be higher in children than adults, as some studies have shown. It is therefore important that studies on metals in urban dust should always incorporate risk assessment as one of the main issues