Traditional biomass stoves increase household air pollution
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In rural areas of Nepal, use of traditional stoves that burn biomass fuel and lack proper ventilation significantly increased indoor exposure to particulate matter and carbon monoxide and were shown to induce inflammatory responses in ex vivo lung tissue, according to research published in the Annals of the American Thoracic Society.
In this study, the researchers measured personal exposure to particulate matter (PM2.5) and indoor near-stove carbon monoxide concentrations during cooking on a range of stoves and during a noncooking period in 103 households in four rural villages in Nepal that were situated at altitudes ranging from 200 m to 4,000 m above sea level.
Ian P. Hall, MD, from the division of respiratory medicine and National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre at the University of Nottingham in the United Kingdom, said he and colleagues opted to conduct the study in Nepal as he had observed many hospital admissions for COPD among women as well as men while working in Dhulikhel Hospital in Kathmandu.
“Nepalese men smoke, but women generally don’t, while they are also traditionally the family cooks. I was interested in why women were getting COPD, and the most obvious question to explore was whether it was due to indoor biomass smoke, so we decided to study these exposures,” he said in a press release.
Increased exposure to indoor pollutants
For all households using traditional biomass stoves in all villages, the overall average personal exposure to PM2.5 was 276.1 µg/m3. In contrast, the average PM2.5 exposure was reduced by 51% (P = .04) in households using biomass fuel in stoves with improved ventilation and by 80% (P < .0001) in households using liquefied petroleum gas stoves. However, even with use of these newer stoves, levels of PM2.5 exposure still exceeded the WHO-recommended safe concentration of 25 µg/m3. Notably, overall average PM2.5 exposures were also higher in the higher-altitude regions of Langtang (746.1 µg/m3) and Salambu (500.6 µg/m3) than in the lower-altitude regions of Pokhara (211.9 µg/m3) and Chitwan (121.9 µg/m3).
The overall average indoor carbon monoxide concentration was also high (16.3 ppm) in households using traditional biomass stoves. Similar to the results observed with PM2.5 exposure, carbon monoxide concentrations were reduced by 72% (P = .0002) in households using stoves with improved ventilation and by 86% (P < .0001) in households using liquefied petroleum gas stoves. Additionally, carbon monoxide levels in exhaled breath from people using traditional biomass stoves was higher during cooking than during noncooking periods.
Effects on lung inflammation
The researchers also exposed surgically removed lung tissue to smoke extracts collected during cooking and tested for 17 different inflammatory substances. Lung tissue was obtained from nine men and five women with a mean age of 62.6 years. Of these patients, 11 were ex-smokers, two were current smokers and two were never-smokers. Fifty-two smoke extract samples including 33 samples from biomass combustion in traditional stoves, 10 samples from biomass combustion in stoves with improved ventilation and six samples from liquefied petroleum gas stoves were collected.
Results showed that levels of seven of 17 inflammatory substances increased in the lung tissue after biomass smoke exposure from traditional stoves. However, the researchers also found that exposure to smoke extract samples from stoves with improved ventilation still induced inflammatory responses related to six of the 17 inflammatory substances and smoke extract samples from liquefied petroleum gas stoves activated two inflammatory substances in lung tissue.
“Little was previously known about the mechanisms underlying the lung’s response to biomass smoke,” Hall said in the release. “Now, we have shown, for the first time, that biomass smoke samples collected in a real-life environment from rural Nepal have proinflammatory effects on human lung tissue. These exposures, which induce lung inflammation, may partially explain the increased risk of COPD in these communities.”
Implications
The researchers noted that the study had limitations, including difficulty in accurately modeling true lung exposures, the potential for underestimation of true inflammatory effects and true local exposure in the lung due to the study’s design and the fact that biomass smoke contains a number of potentially active compounds that will drive inflammatory responses.
Overall, though, the results indicate that exposure to pollutants is higher with use of traditional biomass stoves, which are common in rural areas of developing nations, according to the researchers.
“These data support the need to reduce exposures in order to improve respiratory health in this setting,” Hall said in the release. “Additional methods other than those being tried may be needed to reduce exposures to levels that will prevent lung inflammation and reduce the risk of developing COPD.” – by Melissa Foster
Disclosure: Healio Pulmonology could not confirm the authors’ relevant financial disclosures at the time of publication.