Acute lower respiratory infections (ALRI) contribute to nearly 20% of child mortality globally. Household air pollution (HAP) from burning biomass fuels is a potentially modifiable risk factor of childhood ALRI in developing countries. A large proportion of rural communities in developing countries, where childhood ALRI burden is high, use open fire and biomass fuels for cooking indoors. The three epidemiologic studies in this dissertation aimed to improve our understanding of HAP effects of on childhood ALRI.
The first study (aim 1) evaluated the effectiveness of improved-combustion biomass stoves in reducing HAP and their acceptability to users in rural Western Kenya. In this pre-/post- intervention study, we compared 48-hour mean personal and kitchen concentrations of particulate matter <2.5μm in diameter (PM2.5, μg/m3) and carbon monoxide (CO, ppm) during use of six improved combustion cookstoves to those observed with traditional 3-stone fire in 45 households. We assessed improved stove acceptability through interviews and focus groups. Reductions in kitchen PM2.5 and CO ranged by stove type from 11.9% to 42.3% and from -5.8% to 34.5%, respectively. Mean kitchen PM2.5 (319 to 518µg/m3) were still considerably higher than WHO indoor air quality guidelines. Women found these stoves acceptable for use but also reported limitations for each. Achieving maximal potential of improved stoves requires adherence to more exclusive use and addressing user reported limitations.
The second study (aim 2) evaluated the levels of HAP associated with childhood ALRI through systematic review of literature. We identified 32 studies of household or ambient air pollution, or of second hand smoke effects on ALRI. We conducted meta-analysis and examined the dose-response relationship between PM2.5 and childhood ALRI risk. We found a weak positive association (RR 1.04; 95% CI 1.03, 1.06) and a positive dose-response relationship between the levels of exposure to PM2.5 and ALRI risk. However, due to high level of heterogeneity, the summary estimate should be interpreted with caution. High-quality intervention-based evidence with personal exposure assessment is needed to better quantify exposure-disease relationship.
Lastly, in a prospective cohort study in rural Peru, we evaluated an association between HAP and carriage of Streptococcus pneumonia (pneumococcus), one of the major bacterial causes of ALRI in children (aim 3). We found no association between kitchen and personal CO levels and density of pneumococcal carriage. More efficient biomass stoves and stoves utilizing clean fuels are needed to achieve measurable health benefits.
Results of these studies will help guide policy decisions targeting improvements to indoor air quality to maximize health benefits. The findings of this dissertation should assist organizations working on HAP research and help identify effective stove interventions and potential confounders for further intervention studies of HAP effects on ALRI.
Table of Contents
Introduction and Relevance.. 1
Specific aims. 3
Literature Review... 4
Household air pollution and acute lower respiratory diseases. 4
Exposure assessment in studies of household air pollution and health effects. 6
Preliminary studies in rural Kenya. 10
Case definitions for pneumonia and implications for intervention trials and observational studies. 12
Biological mechanism for the association between household air pollution and pneumonia. 15
Streptococcus pneumoniae as a major cause of pneumonia in children.. 16
Pneumococcal carriage and risk factors. 16
Density of pneumococcal carriage. 18
Effectiveness of six improved cookstoves in reducing household air pollution and their acceptability in rural Western Kenya.. 20
Appendix 1. Seven cookstoves assessed in the study. 53
Appendix 2. Quality Assurance for Exposure Assessment Methods. 54
Appendix 3. Causal Diagram for the Association between Stove Type and IAP.. 55
Estimating the impact of indoor air pollution on childhood pneumonia using meta-regression.. 56
Household air pollution and density of nasopharyngeal carriage of Streptococcus pneumoniae among young children in rural Peru.. 82
Appendix 1. Completeness of nasopharyngeal (NP) sample collection.. 103
Appendix 2. Results of sensitivity analyses for mixed effects models. 104
List of Abbreviations. 123
List of Tables. 124
List of Figures. 125
About this Dissertation
|Committee Chair / Thesis Advisor|
|Evaluation of the effects of clean-burning cookstoves on indoor air pollution and their effects on acute respiratory diseases among children ()||2017-11-10||