Impact of Household Air Pollution on Childhood Linear Growth and Health, in Jimma Town, Oromia Region, Ethiopia

Abstract

Background: Stunting, defined as impaired linear growth and development in children, remains a significant public health challenge, particularly in low- and middle-income countries. It is commonly attributed to factors such as chronic undernutrition, recurrent infections, and poor overall health conditions. While inadequate diet and illness have traditionally been identified as the primary causes of stunting, recent evidence highlights the growing role of environmental factors especially household air pollution in contributing to growth impairments. Exposure to indoor air pollutants has been associated with multiple adverse health outcomes, including childhood stunting and risk of multimorbidity. The leading cause of household air pollution is the widespread use of biomass fuels such as wood, charcoal, and dung for cooking. This practice is particularly prevalent in resource-constrained settings and has emerged as a pressing global health concern. According to the World Health Organization (WHO), more than three billion people worldwide rely on polluting fuels, with approximately 95% of them residing in low- and middle-income countries. The relative contribution of household air pollution to childhood linear growth impairments and the risk of multimorbidity in Ethiopia remains underexplored. While some global studies have highlighted the adverse health effects of indoor air pollution on young children, there is a scarcity of context-specific evidence from Ethiopia that quantifies this relationship, particularly in urban settings like Jimma town. Therefore, this study aims to investigate the impact of household air pollution on linear growth and the risk of multimorbidity in children under five years of age in Jimma town, Ethiopia. Objectives: The main objective of this study is to investigate the impact of household air pollution on the linear growth and health of under-five children in Jimma town, Ethiopia. Methods: To synthesize the global and local evidence on the impact of household air pollution on childhood linear growth, this study employed a combination of systematic review and meta analysis, comparative cross-sectional analysis, and a prospective cohort design. A total of 280 under-five children, with 140 residing in households that use solid fuels (exposed group) and 140 in households that use clean fuels (unexposed group) were involved for the primary studies. The children's height and height-for-age Z scores (HAZ) were measured and compared over a 12 month follow-up period to assess differences in linear growth between the two groups. Environmental exposure was evaluated by measuring real-time concentrations of indoor air pollutants. These included particulate matter (PM₂.₅ and PM₁₀), carbon monoxide (CO), carbon dioxide (CO₂), and volatile organic compounds (VOCs), using Laser PM2.5 Meter-5800D/5800E and Aeroqual’s TM Series 500 portable air quality monitors, respectively. Additionally, data on childhood morbidity were collected using the Ethiopian Demographic and Health Survey (EDHS) morbidity questionnaire, administered to mothers to capture information on common illnesses experienced by their children. Analytically, difference-in-differences estimators were used to compare changes in height and HAZ scores between baseline and endline across the two groups. A multivariable linear regression model was applied to assess the independent effect of solid fuel use on HAZ scores. Furthermore, multiple logistic regression was employed to explore the association between household solid fuel use and the likelihood of childhood multimorbidity, xii while Poisson regression was used to examine whether exposure to solid fuels increased the number of reported morbidities. Statistical significance was determined at a p-value of less than 0.05 with corresponding 95% confidence intervals Results: The results of systematic review and meta-analysis indicate that exposure to household air pollution was significantly associated with increased odds of child stunting [pooled estimate: Odds Ratio = 2.42, (95% CI: 1.45, 4.03), P < 0.0010]. Likewise, children who were exposed to household air pollution from cooking with solid fuels had significantly lower HAZ scores than children who lived in households where cleaner fuels were used [Standardized Mean Difference = 0.41, (95% CI: 0.12, 0.71), p < 0.001] (Chapter 4). The findings of quantitative measurements of Household Air Pollution showed that the mean (SD) and median concentrations of pollutants in all measured households were: PM2.5; 455 (386) and 294 µg/m3, PM10; 819 (829) and 270 µg/m3, CO2; 787 (488) and 577 mg/m3, CO; 12 (13.9) and 7.9 mg/m3, and VOC; 1154 (861) and 1077 mg/m3. Households using solid fuels had significantly higher concentration of PM2.5 (U = 53.0, Z = -14.436, p < 0.001), PM10 (U =63.0, Z = -14.502, p < 0.001), CO2 (U = 3519.50, Z = -7.273, p < 0.001), CO (U = 3246.0, Z = -4.445, p < 0.001) and VOC (U = 2073.0, Z = -11.40, p < 0.001) than households using clean fuel (Chapter 5). The results of the assessment of the Impact of Indoor Air Pollution on the Linear Growth of Children, compared with the clean fuel type, revealed that in an unadjusted model (Model 1), the mean difference in the height-for-age Z score of children in households using solid fuel was lower by 0.54 (-0.54, 95% CI -0.97, -0.12, P = 0.011). The beta coefficient remained negative after adjusting for age and sex (Model 2 -0.543, 95% CI -1.373, -0.563) and sociodemographic variables (Model 3: -0.543, 95% CI -1.362, -0.575). In the final model (Model 4), which adjusted for wealth quantile, dietary practice, water, sanitation and hygiene status and household food insecurity access scale, the beta coefficient held the same and significant (beta: -0.543, 95% CI -1.357, 0.579, P < 0.001) (Chapter six). In the findings of the investigation of Exposure to Household Air Pollution and Childhood Multimorbidity Risk, the overall prevalence of childhood multimorbidity was 34.3% [95% CI: 0.29–0.40]. Among these cases, 23.9% was among children from solid fuel user households, whereas about 10.4% was from clean fuel user households. Adjusted for all possible covariates, children living in solid fuel user households had more than three times the odds of childhood multimorbidity compared to children living in clean fuel user households (AOR = 3.14, 95% CI [1.42–6.95], p < 0.001). Moreover, household air pollution from solid fuel use was positively associated with an increased number of individual morbidity conditions, with an adjusted β coefficient of 0.46 (IRR = 1.58, 95%CI [1.17-2.13], p = 0.003) (Chapter 7). In conclusion, indoor air pollution was negatively associated with childhood linear growth, and solid fuel use independently predicted morbidity risk. Addressing this requires public education on health risks and promoting better kitchen ventilation and improved cooking stoves to reduce child growth impairments and multimorbidity (Chapter 8).