Summary: Indoor air pollution is a major cause of death and disease, especially for the poor who rely on solid fuels for cooking and heating. However, the world has made remarkable progress in reducing indoor air pollution and its health impacts in recent decades. Millions of lives have been saved through the adoption of cleaner fuels and technologies.

One day your youngest daughter develops a nasty cough. Smoke from the indoor fire is weakening her lungs. You can’t afford antibiotics, and one month later she is dead. This is extreme poverty.

Hans Rosling, Ola Rosling, and Anna Rosling Rönnlund, Factfulness: Ten Reasons We’re Wrong about the World—and Why Things Are Better Than You Think

Millions of people in Canada and the United States have suffered abysmal indoor and outdoor air quality this summer because of hundreds of wildfires in Quebec. It’s easy to forget that most humans were subjected to crippling indoor air quality for nearly all of history. Our mastery of fire as hunter-gathers provided warmth for heating, cooking, and forging tools; however, it also made air pollution part of our daily lives. As humanity transitioned from hunting and gathering to settled farming, we took our fires with us into our enclosed dwellings, bringing the resulting air pollution with it.

Indoor heating and cooking obviously have enormous practical value and undoubtedly improved living standards; a warm shelter and a hot meal are certainly valued in cold weather. The fire and resulting heat aren’t the issues; incomplete combustion and the smoke and toxic particulate byproducts wreak havoc on health and well-being. Civilization’s long history of indoor air pollution has been a slow transition to cleaner heating and cooking fuels, with families adopting cleaner fuel sources as swiftly as technology and income allow.

The first fuels we harvested from nature were also the most inefficient—plant material, dung, wood, charcoal, and coal—producing the least heat per unit and the most pollution and crop waste. There has always been a direct link between the quality of heating fuels and their cost, and thus poorer families have, by economic necessity, been exposed to the greatest burden of indoor air pollution. Over the last hundred years, global economic growth has allowed hundreds of millions of families to switch from poor-quality solid fuels to less polluting liquid and gas fuels and, ultimately, to natural gas and electricity where available and affordable. As countries transition from low and middle income to high income, both indoor and outdoor air pollution decreases. Today indoor air pollution, largely generated by burning solid fuels in and around the home, remains a driver in reducing life expectancy and increasing child mortality for poor families living in low- and middle-income countries, most particularly impacting women, children, and the elderly.

In 2019, indoor air pollution was estimated to claim roughly 2.4 million lives annually, comprised largely of people living in the world’s poorest regions in Africa and Southeast Asia, totaling some 4 percent of all deaths globally. The good news is that global economic growth is fueling the solution to improving indoor air quality for the world’s poor, namely access to cleaner fuels. This transition is having a profound impact on death rates from indoor air pollution, as well as lifting living standards by freeing women and children from the arduous task of gathering and processing solid fuels for heating and cooking each day. Between 2000 and 2020, the share of the global population with access to clean fuels for heating and cooking grew from 49 percent to 69 percent, helping to considerably reduce the burden of air quality–related disease and death. Between 1990 and 2019, the annual number of premature deaths attributed to household air pollution from the use of solid fuels for cooking fell by a little over two million deaths. That’s a reduction of nearly 50 percent globally in three decades, and the trajectory is continuing in the right direction; with each passing year, more families are able to make the switch to lifesaving, cleaner-burning fuels.

The story is much the same for outdoor air pollution, in which civilization has three distinct phases. First, early industrialization powered by coal and other hydrocarbons, limited or absent environmental regulation, and inefficient and polluting manufacturing processes have belched high levels of air pollution into the environment. Second, countries transitioning from low-income to middle-income status have improved regulation, reduced highly polluting sources of manufacturing, and generated considerably less air pollution. Finally, in the most highly developed countries, pollution regulation, paired with gasification and electrification, have improved air quality further.

Economic growth and regulation have allowed the world to experience a remarkable reduction in many of the air pollutants that are harmful to human health and damaging to the environment. Progress on improving both outdoor and indoor air quality unfortunately has not been universal, and it is the world’s poor, living in low- and middle-income countries, that still suffer the most. If there’s one statement that can be made about indoor and outdoor air pollution, it is that individual wealth and a country’s gross domestic product determine to a large degree how much pollution the average individual living in the region will suffer. Better economic opportunity at the individual and national levels means cleaner air almost every time. Progress in the right direction certainly does not mean that all is well. In 2019, indoor and outdoor air pollution combined claimed the lives of roughly 6.8 million people, leaving a great deal of room for improvement before we can celebrate victory over air pollution.

Much of the developing world is moving toward cleaner air—albeit slowly in some cases— saving millions of lives annually. And while that is little comfort for many, including those who suffer under blankets of toxic wildfire smoke, it’s worth being thankful that air pollution, which used to be the norm in the industrializing world, is now the exception rather than the rule in much of the developed world.