Humans have been harnessing fire for millions of years, and today nearly 40% of Earth’s population uses solid fuel like wood, hay, dung, charcoal, and coal to heat their homes and cook their meals. However, breathing in the soot and ash particles that these fuels emit when burned can be harmful. Fine particles—known as PM2.5 since they are, at most, 2.5 micrometers in diameter—are able to travel deep into the lungs. With long-term exposure, they can lead to pneumonia, pulmonary disease, and lung cancer.
Here Kodros et al. study the impact of solid-fuel use on premature death. This topic has been examined extensively, but past studies have primarily looked at PM2.5 exposure within households and in the open air as separate entities, whereas this study considers PM2.5 exposure as a whole. The researchers also tested highly sensitive parameters to show the uncertainty with which premature deaths can be attributed to the use of solid fuels.
The researchers examined data on all deaths across the globe caused by exposure to PM2.5, both in the home and outdoors, during 2015. They used a mathematical model to estimate that PM2.5 exposure from solid-fuel use was responsible for around 2.8 million premature deaths that year. They also found that if they had calculated household and open-air exposure deaths separately, their total estimate would have been about 18% higher—a major difference.
Although combining the two sets of data is an improvement over past studies, the team’s calculations show that the method still has large uncertainties in the relationship between PM2.5 exposure and premature death. The factors that introduced the most uncertainty in their estimates varied by country. For example, in India, China, and Latin America, it is unclear exactly what percentage of the population uses solid fuels for heating and cooking, which directly leads to uncertainties in estimates of deaths attributed to solid-fuel smoke. Conversely, in sub-Saharan Africa, where a known, large percentage of the population uses solid fuels, the uncertainty in the underlying health data (i.e., records of what diseases people died from) is the leading contributor to the uncertainty in the researchers’ estimates.
This study provides a solid reference point for future research looking to improve estimates of deaths attributed to solid-fuel use. In the event that better data become available from these regions, scientists will be better equipped to make more accurate estimates—and help people around the world reduce their exposure to harmful pollutants. (GeoHealth, https://doi.org/10.1002/2017GH000115, 2018)
—Sarah Witman, Freelance Writer