Human Journey

“Catching air”: Measuring the amount of indoor air pollution we breathe and how it impacts our health

Every year, 6.5 million people die from exposure to air pollution 1,2. Indoor air pollution from burning solid fuels (e.g., coal, wood) inefficiently in open fires or traditional stoves accounts for ~40% of air pollution mortality and is considered to be one the top leading environmental risks to human health 1. The good news is, indoor air pollution can be eliminated. Interventions of improved stoves that burn solid fuels efficiently and cleanly could have a major impact on the health of millions of people around the world. However, most previous ‘improved’ stove interventions have failed to reduce indoor air pollution levels low enough to reach international targets set by the World Health Organization 3.

This photo essay portrays household air pollution and its impacts on cardiovascular health in rural Chinese communities in the Tibetan Plateau mountains, and the field-work activities of an international team trying to study the effectiveness of an improved cookstove intervention to address it (for more information on the study, see references to peer-reviewed published papers below) 4–9.

Image 1. Approximately half of the people in the world are exposed to indoor air pollution from burning solid fuels (e.g., wood, coal) inefficiently in traditional stoves or open fires 10. In this image, water is heated on a traditional chimney stove fuelled by coal in Shanxi, Province, China.

Image 2. In China, approximately half (~600 million people) of the population 10, mostly rural, relies on solid fuels for cooking and heating. A woman is standing over her traditional woodfuel chimney stove in Sichuan Province, China, where smoke can easily escape through the stove’s open combustion chamber.

Image 3. Cooking with solid fuels also contributes to outdoor pollution levels, globally, this contribution is 12% 11. A woman smokes meat in Sichuan Province, China, over an outdoor wood fire.

The economic, social, and health burden of cooking and heating with solid fuels largely falls on women. Due to traditional gender norms in many places of the world, the job of harvesting and collecting firewood for fuel is assigned to women. This activity is not only unpaid, but it also takes time away from other potential income generating activities 12. Additionally, women are typically expected to prepare the majority of meals for the household, which means that women will spend more time in the kitchen and near the sources of pollution 13. A woman in the Tibetan Plateau, China comes back from the forest where she harvested and collected firewood for fuel.

Image 5. Young children are particularly vulnerable to the health impacts of indoor air pollution. Not only are they biologically more vulnerable than adults, but they also may spend more time near the sources of pollution (i.e., indoors). A young girl sits on her couch and watches a research team collect air pollution measurements in her household, Sichuan Province, China.

Image 6. An international team of researchers and local field-staff worked together to collect samples of indoor air pollution in the Tibetan Plateau, China (2014-2017) and evaluate whether an improved cookstove intervention could reduce exposures and improve indicators of cardiovascular health. The field-work van is parked alongside the road while the team collects measurements in a participating household high up in the mountains.

Image 7: Collecting samples of particulate matter pollution (PM2.5, particulate matter with aerodynamic diameter <2.5 micrometers) provides an indication of how much pollution people are exposed to on a daily basis. The field team cleans and prepares the air pollution monitoring equipment for deployment in homes the following day, Sichuan Province, China.

Image 8: Kitchen concentrations of air pollution can be collected with stationary monitors set up inside households. However, collecting personal exposure samples of air pollution is a more relevant metric for health studies 14. Women wear a waist pack with an air pollution monitor inside. Women wear the waist pack for 48h which gives an indication of the daily levels of personal pollution exposure.

Image 9. Air and pollution are drawn through the air pollution monitor by an attached battery powered pump. The particulate matter pollution (PM2.5, particulate matter with aerodynamic diameter <2.5 micrometers) then collects on a filter that is placed inside the monitor. After 48h of sampling, filters with PM2.5 are stored in petri dishes and transported to laboratories in the USA where they are weighed for their total mass (i.e., how much pollution) and chemically analyzed for their chemical composition (i.e., what is in the pollution) 9. Filters with different amounts and types of particulate matter pollution are prepared for chemical analysis at an air pollution laboratory at the University of Wisconsin-Madison.

Image 10. There is evidence to suggest that exposure to air pollution is associated with arterial stiffness, which is a risk factor for cardiovascular disease events and mortality, independent of blood pressure and hypertension 15,16. A participant in Sichuan, China, has her carotid-femoral pulse wave velocity taken, which is a gold-standard metric of arterial stiffness.

Image 11. High systolic and diastolic blood pressure are known risk factors for cardiovascular disease events and mortality and associated with exposure to outdoor an indoor air pollution 16,17. A participant in Sichuan, China, has her blood pressure taken following 48h of air pollution monitoring.

Image 12. Exposure to air pollution is associated with the development of atherosclerosis (i.e., plaque build up in arteries) which is a major risk factor for cardiovascular disease events and mortality 18. A teammate in Shanxi Province, China, has his carotid arteries scanned with an ultra-sound for carotid intima media thickness (CIMT) and number of plaques during a training session, 2016.

Image 13. Improved cooking and heating stoves can potentially reduce exposure to air pollution by burning solid fuels more cleanly and efficiently and improve cardiovascular health. The Tsinghua University semi-gasifier stove burns pelletized wood as fuel and is a top preforming stove in laboratory based studies 19. The stove was iteratively developed over five years, taking user-preferences and needs into the design process 5.

Photos credit: All photos were taken by the author of this post, Sierra Clark.

References:

  1. Gakidou, E. et al. Global, regional, and national comparative risk assessment of 84 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2016 a systematic analysis for the Global Burden of Disease Study 2016. Lancet 390, 1345–1422 (2017).
  2. Landrigan, P. J. et al. The Lancet Commission on pollution and health. Lancet 6736, (2017).
  3. WHO. Indoor Air Quality Guidelines: Household Fuel Combustion. World Health Organization (2014).
  4. Ni, K. et al. Seasonal variation in outdoor, indoor, and personal air pollution exposures of women using wood stoves in the Tibetan Plateau: Baseline assessment for an energy intervention study. Environ. Int. 94, 449–457 (2016).
  5. Shan, M. et al. A user-centered iterative engineering approach for advanced biomass cookstove design and development. Environ. Res. Lett. (2017). doi:https://doi.org/10.1088/1748-9326/aa804f
  6. Carter, E. et al. Seasonal and Diurnal Air Pollution from Residential Cooking and Space Heating in the Eastern Tibetan Plateau. Environ. Sci. Technol. (2016). doi:10.1021/acs.est.6b00082
  7. Shan, M., Yang, X., Ezzati, M., Chaturvedi, N. & Coady, E. A feasibility study of the association of exposure to biomass smoke with vascular function, inflammation, and cellular aging. Environ. Res. 135, 165–172 (2014).
  8. Clark, S. et al. Adoption and use of a semi-gasifier cooking and water heating stove and fuel intervention in the Tibetan Plateau, China. Environ. Res. Lett. 12, (2017).
  9. Secrest, M. H. et al. The oxidative potential of PM2.5 exposures from indoor and outdoor sources in rural China. Sci. Total Environ. 571, 1477–1489 (2016).
  10. Bonjour, S. et al. Solid fuel use for household cooking: Country and regional estimates for 1980 – 2010. Environ. Health Perspect. 784, 784–791 (2013).
  11. Chafe, Z. A. et al. Household cooking with solid fuels contributes to ambient PM2.5 air pollution and the burden of disease. Environ. Health Perspect. 122, 1314–1320 (2015).
  12. Jeuland, M., Pattanayak, S. K. & Bluffstone, R. The Economics of Household Air Pollution. Annu. Rev. Resour. Econ. 7, 81–108 (2015).
  13. USAID. Evidence Brief on Clean Cooking to Protect Maternal and Child Health. (2017).
  14. Clark, M. L. et al. Health and Household Air Pollution from Solid Fuel Use: The Need for Improved Exposure Assessment. Environ. Health Perspect. 1120, 1120–1128 (2013).
  15. Brook, R. D. et al. Air Pollution and Cardiovascular Disease. Circulation 109, 2655–2671 (2004).
  16. Brook, R. D. et al. Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the american heart association. Circulation 121, (2010).
  17. McCracken, J. P. et al. Household Air Pollution from Solid Fuel Use: Evidence for Links to CVD. Glob. Heart 7, 223–234 (2012).
  18. Painschab, M. S. et al. Chronic exposure to biomass fuel is associated with increased carotid artery intima-media thickness and a higher prevalence of atherosclerotic plaque. Heart 99, 984–991 (2013).
  19. Carter, E. M., Shan, M., Yang, X., Li, J. & Baumgartner, J. Pollutant emissions and energy efficiency of Chinese gasifier cooking stoves and implications for future intervention studies. Environ. Sci. Technol. 48, 6461–6467 (2014).

Acknowledgements

Many thanks to the women in Sichuan Province, China, who participated in our three-year long air pollution, health, and intervention monitoring study, and to our project manager, Niu Hongjiang, and field staff (He Lan, Zhang Qing, Zhu Rong, and Wang Yu) for making data collection happen. Sierra Clark was supported by a National Geographic Young Explorers grant in summer 2016 for her field work in Sichuan, China. Sierra’s work was nested within a U.S. Environmental Protection Agency (EPA) funded project on air quality, climate and health led by Jill Baumgartner at the University of Minnesota/McGill University. The EPA did not review this photo essay and the views and content are solely the responsibility of the author.

Larger project title: IGNITE study: Improving air quality, health and the environment through household energy interventions in the Tibetan Plateau

Project Principal Investigator: Dr. Jill Baumgartner, McGill University, jill.baumgartner@mcgill.ca

For more information on the Sichuan cookstove intervention study (IGNITE), refer to the following peer-reviewed publications:

Carter, E. et al., 2016. Seasonal and Diurnal Air Pollution from Residential Cooking and Space Heating in the Eastern Tibetan Plateau. Environmental Science and Technology.

Carter, E.M. et al., 2014. Pollutant emissions and energy efficiency of Chinese gasifier cooking stoves and implications for future intervention studies. Environmental Science & Technology, 48(11), pp.6461–6467.

Clark, S. et al., 2017. Adoption and use of a semi-gasifier cooking and water heating stove and fuel intervention in the Tibetan Plateau, China. Environmental Research Letters, 12.

Shan, M. et al., 2014. A feasibility study of the association of exposure to biomass smoke with vascular function, inflammation, and cellular aging. Environmental Research, 135, pp.165–172.

Shan, M. et al., 2017. A user-centered iterative engineering approach for advanced biomass cookstove design and development. Environmental Research Letters.

Ni, K. et al., 2016. Seasonal variation in outdoor, indoor, and personal air pollution exposures of women using wood stoves in the Tibetan Plateau: Baseline assessment for an energy intervention study. Environment International, 94, pp.449–457.

Secrest, M.H. et al., 2016. The oxidative potential of PM 2 . 5 exposures from indoor and outdoor sources in rural China. Science of the Total Environment, 571, pp.1477–1489.

Sierra Clark attended McGill University (Montreal, Canada) for her Bachelor of Arts Degree in Geography, McGill University for her Masters Degree in Epidemiology, and she was an international research fellow at the University of Wisconsin-Madison (2017). Sierra is passionate about field-based research and has worked in Uganda and China to collect data, and explore the connections between, a changing climate, air pollution, and health. Sierra is passionate about conducting science to inform evidence-based policies, and she is currently evaluating whether an improved cookstove intervention in the Tibetan Plateau, China can reduce exposures to household pollution and improve cardiovascular health. Sierra is a proud National Geographic Explorer, and excited about science communication and outreach for impact. Twitter: @sierraclark2 Email: sierra.clark@mail.mcgill.ca National Geographic profile page: https://www.nationalgeographic.org/find-explorers/explorers/CF78DED4/sierra-n-clark

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (dbraun@ngs.org)

Social Media