The health effects of using gaseous fuels for household cooking and heating

In a recent systematic review and meta-analysis published in The Lancet Respiratory Medicine, researchers examined the evidence on the health effects of the use of gaseous fuels for heating and cooking in various countries. They found that transitioning from polluting fuels to gaseous fuels for household purposes may reduce health risks, particularly in low-income countries.

Background

Household air pollution from solid fuel combustion causes 3.2 million preventable deaths annually. Transitioning to clean liquid and gaseous fuels, crucial for low- and middle-income countries (LMICs), is recognized to address this burden. The present study synthesizes evidence on the health effects of domestic use of liquid and gaseous fuels, emphasizing the urgent need for a clean transition to meet Sustainable Development Goals. Despite electricity being the cleanest, its limited accessibility in LMICs necessitates scalable alternatives.

This systematic review and meta-analysis explored the health impacts of gaseous and liquid fuels, excluding polluting liquid fuels (solid fuels, kerosene) for lighting, and highlights the potential respiratory effects of gas usage, informing global policies for a swift transition to cleaner household energy.

About the study

For the systematic review, major databases, including PubMed, Scopus, MEDLINE, Cochrane Library, Environment Complete, Web of Science, GreenFile, Wanfang DATA, Google Scholar, and CNKI were searched. Studies published between 1980 and 2021 focusing on the health effects of cooking and heating with liquid and gaseous fuels (natural gas, liquefied petroleum gas (LPG), biogas) were selected. Studies related to lighting or specific pollutants with no health outcome were excluded. A total of 216 studies were included in the systematic review, while 116 studies were included in the meta-analysis.

Data was extracted using an Excel form refined over 15 rounds, capturing study details, fuel types, comparators, population characteristics, health outcomes, and results. Liverpool Quality Assessment Tools (LQATs) assessed study quality, considering aspects like selection, response bias, exposure measurement, and confounding. Quality scores (as percentages) were categorized into at least moderate quality (>60%) and poorer quality (≤60%). This approach aimed to evaluate the potential impact of methodological quality on pooled effect estimates in meta-analyses without assuming a hierarchy of evidence.

Meta-analyses focused on five health effects: asthma (child and adult), acute lower respiratory infections, chronic lung disease, respiratory symptoms, and adverse pregnancy outcomes. Studies with consistent definitions for health conditions and exposure to any gaseous fuel for household energy were pooled for analysis. Random-effects meta-analysis was employed, and adjusted estimates were preferred. Funnel plots and statistical tests assessed publication bias. Forest plots were stratified by age group and condition. Separate analyses compared gaseous or liquid fuels to clean (electricity) and polluting (wood, charcoal, kerosene) reference groups, with sensitivity analyses for studies with unclear reference groups.

Results and discussion

As per the study, gaseous fuels demonstrated a 35% lower risk of asthma in adults compared to polluting fuels. However, no significant difference was observed in asthma risk for children. For acute lower respiratory infections or pneumonia, cooking with gas lowered the risk by 46% when compared to polluting fuels but increased the risk by 26% compared to electricity.

Gaseous fuels were associated with a significant 64% lower risk of chronic lung diseases, including chronic obstructive pulmonary disease and bronchitis. Adverse pregnancy outcomes such as preterm birth and low birth weight showed lower risks (34% and 30% reduction, respectively) when using gas for cooking compared to polluting fuels.

Further, gaseous fuels were linked to a 58% lower risk of wheezing but exhibited a non-significant increase in the risk of cough compared to electricity. Breathlessness risk was significantly lower with gas use compared to polluting fuels.

This is the first study to systematically review the global health effects of gaseous fuels (for household cooking and heating. Unlike previous reviews, it comprehensively considers various health outcomes and assesses both polluting and clean (electricity) reference options.

Conclusion

In conclusion, switching from solid fuels or kerosene to clean gaseous fuels for cooking or heating is associated with a significantly lower risk of key health outcomes, contributing to a reduction in the global disease burden from pollution. In low- and middle-income countries, where the burden is highest, gaseous fuels (particularly LPG) represent an effective short-to-medium-term option for scalable adoption. However, there’s a slight increase in risk when using gaseous fuels compared to electricity.

Electricity may remain the priority for clean cooking where feasible, emphasizing the transitional role of gaseous fuels in regions without access to renewable electric alternatives. The findings contribute crucial evidence for informing clean-energy policies at the national level, particularly in low-income and middle-income countries, to address the health burden associated with household air pollution effectively.