Authors:

Authors: 

John Mwangi¹, 

Aisha Bello², 

David Okeke³
¹Machakos County Referral Hospital | ²Abuja General Hospital | ³Anambra State Health Institute

Abstract

Childhood asthma is a growing public health concern, particularly in densely populated informal settlements with poor indoor air quality. This study investigates the relationship between indoor smoke exposure and asthma severity in children residing in informal settlements of Nairobi. A cross-sectional survey involving 300 households was conducted. Findings indicate a strong positive correlation between the use of biomass fuels for cooking and increased asthma exacerbations, particularly among children under 10 years. The study underscores the urgent need for policy interventions promoting cleaner cooking technologies in urban low-income settings.

Introduction

Indoor air pollution, primarily caused by biomass combustion, is a major contributor to respiratory illnesses globally, particularly in low- and middle-income countries (Smith et al., 2000; Ezzati & Kammen, 2001). In sub-Saharan Africa, the use of firewood, charcoal, and kerosene remains prevalent in informal settlements, where modern energy infrastructure is often lacking (WHO, 2014; Bruce et al., 2000; Bonjour et al., 2013).

Asthma, a chronic inflammatory disease of the airways, is increasingly recognized in African urban areas, where environmental triggers such as smoke and particulate matter are abundant (Ait-Khaled et al., 2007; Zar et al., 2013; Adeloye et al., 2013). Despite this recognition, the specific role of indoor smoke in exacerbating asthma severity remains underexplored in densely populated settlements like those in Nairobi (Kimani-Murage et al., 2015; Mberu et al., 2016).

The pathophysiology of asthma involves airway hyper-responsiveness, mucus hypersecretion, and inflammation, processes that can be intensified by chronic exposure to particulate matter and toxic gases from combustion (Balmes, 2019; Gordon et al., 2014). Children are especially vulnerable due to their developing respiratory systems, higher respiratory rates, and prolonged exposure to indoor environments (Smith et al., 2014).

This study by Mwangi, Bello, and Okeke seeks to evaluate how indoor smoke exposure from household cooking fuels correlates with asthma severity among children in Nairobi's informal settlements. Our findings aim to inform public health policy and guide interventions for respiratory health in low-income urban settings.

Methods

Study Area and Design: A community-based cross-sectional survey was conducted between January and July 2024 in three major informal settlements in Nairobi: Kibera, Mathare, and Mukuru kwa Njenga. These areas are characterized by high population density, limited access to basic services, and extensive use of biomass fuels.

Sample Population: Three hundred households with children aged 3–14 years previously diagnosed with asthma were selected using stratified random sampling. Stratification was based on geographical zones and types of cooking fuel used. Informed consent was obtained from all caregivers.

Data Collection Instruments: Data was collected using a combination of structured questionnaires, household observations, and medical chart reviews. Questionnaires adapted from the International Study of Asthma and Allergies in Childhood (ISAAC) were used to assess asthma symptoms and severity (Asher et al., 1995).

Indoor Smoke Exposure Assessment: Household fuel use (charcoal, firewood, kerosene, LPG, electricity), cooking location (indoors/outdoors), ventilation (presence of windows or chimneys), and frequency of cooking were recorded. Observations included signs of soot and indoor smoke accumulation.

Asthma Severity Classification: Asthma severity was categorized according to the Global Initiative for Asthma (GINA) guidelines (GINA, 2020). Severity levels were defined as intermittent, mild persistent, moderate persistent, or severe persistent based on frequency of symptoms, activity limitation, nighttime symptoms, and medication use.

Data Analysis: Data were analyzed using SPSS v26. Descriptive statistics were used to summarize household characteristics and exposure levels. Spearman’s correlation coefficient was used to assess the relationship between indoor smoke exposure and asthma severity. Logistic regression was performed to adjust for potential confounders, including child’s age, gender, nutritional status, parental smoking, and household socioeconomic status.

Results

Of the 300 households, 64% used charcoal, 22% used firewood, and 14% used LPG or electricity as their primary cooking fuel. Cooking was conducted indoors in 71% of households, often in unventilated or semi-enclosed spaces.

Children from households using biomass fuels reported significantly more frequent asthma symptoms. Specifically, the mean asthma severity score (on a 5-point scale) was 3.8 in biomass-using households, compared to 2.1 in households using LPG or electricity (p < 0.001).

There was a strong positive correlation (r = 0.61, p < 0.01) between indoor smoke exposure and frequency of asthma symptoms. Children in biomass-using homes were 3.5 times more likely to experience weekly asthma exacerbations (OR = 3.5; 95% CI: 2.1–5.7).

Nighttime asthma symptoms were reported in 78% of children from biomass-using households, compared to 43% in cleaner fuel households. Emergency health visits in the last 6 months were reported in 34% of children from high-exposure homes.

Discussion

The findings by Mwangi et al. reveal a robust correlation between indoor smoke exposure and childhood asthma severity in informal settlements. These results are consistent with the growing body of evidence linking biomass smoke to adverse respiratory outcomes (Smith et al., 2000; Ezzati et al., 2002; Rumchev et al., 2004).

In households that relied on charcoal and firewood, children were exposed to high concentrations of particulate matter (PM2.5) and carbon monoxide, both known to trigger asthma attacks (Balmes, 2019; North et al., 2019). Chronic exposure to these pollutants can impair lung development and increase the risk of chronic respiratory diseases (Zar et al., 2013; Dherani et al., 2008).

Our findings support the work of Kimani-Murage et al. (2015), who reported that Nairobi's informal settlements suffer from disproportionately poor indoor air quality. Similarly, Mberu et al. (2016) documented a high burden of respiratory symptoms among children in these settings.

Intervention studies, such as those by Hanna et al. (2016) and Grieshop et al. (2011), have shown that switching to cleaner cooking fuels significantly reduces exposure and improves respiratory outcomes. However, affordability and accessibility remain major barriers to widespread adoption in urban informal settlements (Bonjour et al., 2013; Rosenthal et al., 2018).

Policy interventions should therefore focus on increasing access to clean energy, subsidizing LPG, and promoting improved cookstoves. Public health campaigns must also educate caregivers on the risks of indoor smoke and strategies to improve ventilation (Rehfuess et al., 2014; Pope et al., 2010).

Conclusion

This study demonstrates a strong correlation between indoor smoke exposure from biomass fuel use and asthma severity in children living in Nairobi’s informal settlements. Reducing exposure through cleaner fuels, improved household design, and public awareness can significantly mitigate the burden of childhood asthma.

Given the high prevalence of biomass use and the increasing incidence of asthma, immediate multisectoral intervention is required. Collaboration between health agencies, environmental bodies, and local governments is essential to develop sustainable solutions that prioritize the health of vulnerable populations.

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