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Solid fuel cooking linked to higher respiratory death rate

Research makes a 'compelling case to speed up universal access to affordable clean energy'

Louise Prime

Friday, 21 September 2018

Chronic and acute respiratory disease hospitalisations or deaths were 36% more likely among people who used wood or coal for cooking compared with those who used electricity or gas to cook – and the longer people used solid fuels, the higher the risk – new research has shown. The authors of the study*, published today in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine, said their results, although observational, “make a compelling case to speed up the global implementation of universal access to affordable clean energy”.

A research team led from the Nuffield Department of Population Health at the University of Oxford – and that included Professor Sir Richard Peto – pointed out that solid fuels emit very high levels of pollutants, especially very small particles that can penetrate deep into the lungs. They added that more than 2.7 billion people, mainly those who live in rural areas of low- and middle-income countries, are regularly exposed to high levels of household air pollution (HAP). Previous cross-sectional and case-control studies have suggested an association between HAP from solid fuel use and excess risk of chronic obstructive pulmonary disease (COPD), but the magnitude of the risk estimates varied greatly across different studies, with several recent larger studies reporting null association.

To investigate further, the team devised a large-scale cohort study to examine the associations between solid fuel use and risks of acute and chronic respiratory diseases. They analysed data from the health records of 277,838 adults, aged 30-79, in the China Kadoorie Biobank (CKB); all participants were never-smokers and were free of respiratory and other major chronic diseases at enrolment.

During nine years’ follow-up, 19,823 first hospitalisation episodes or deaths from major respiratory diseases, including 10,553 chronic lower respiratory disease (CLRD), 4,398 COPD, and 7,324 acute lower respiratory infection (ALRI), were recorded. Overall, 91% of participants reported regular cooking, with 52% using solid fuels.

The researchers adjusted for people’s age, sex, socio-economic status, passive smoking, alcohol drinking, diet, physical activity and obesity. They reported that compared with people who used clean fuels, solid fuel users were at great risk of major respiratory diseases (adjusted hazard ratio, HR 1. 36), whereas those who switched from solid to clean fuels had weaker (but still statistically significant) excess risk (HR 1.14). The HRs were higher among wood (1.37) than coal users (1.22) and in those with prolonged use (≥40 years 1.54, <20 years 1. 32), but lower among those who used ventilated rather than non-ventilated cookstoves (1.22 vs 1.29). For CLRD, COPD and ALRI, the HRs associated with solid fuel use were, respectively, 1.47, 1. 10 and 1.16.

The study authors commented that although their research was observational and so could not show causation, it “provides suggestive evidence that improved ventilation or switching to clean fuels may alleviate the excess respiratory risks associated with solid fuel use”.

They concluded: “Although we cannot infer a causal relationship from these observational findings, our findings make a compelling case to speed up the global implementation of universal access to affordable clean energy, one of the United Nations Sustainable Development Goals.”

*Chan KH, Kurmi OP, Bennett DA, et al. Solid fuel use and risks of respiratory diseases: a cohort study of 280,000 Chinese never-smokers. American Journal of Respiratory and Critical Care Medicine, published online first 21 September 2018. DOI:10.1164/rccm.201803-0432OC

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