Cook Stoves and Pollution Mortality

Image courtesy of Breanna Brownson.

Nowhere is the diversity in the impacts of climate change more obvious than in India. There, great disparities in people’s access to pollution-causing technologies ultimately culminate in stark differences in health and lifespan. Pollution is the single greatest environmental cause of premature mortality worldwide, but the proportion of Indian babies and moms dying from it vastly exceeds the global average. 

While researchers have long studied the tie between emission origin and pollution spread, as well as the impacts of this pollution on human health, these disciplines had historically remained unconnected. The question of why families located in specific areas of India disproportionately felt the impacts of atmospheric pollution lingered. 

To correlate the hotspots of pollution-based premature mortality with proximity to emission-causing technologies in India, Narasimha Rao, an associate professor at the Yale School of the Environment, assembled a team of researchers from Yale and the International Institute for Applied Systems Analysis with different areas of expertise. Serving as climate justice advocates, they sought to understand the income-specific impacts of pollution and to propose policies to address these interconnected disparities in India.

The Integration of Models

Climate change models have existed as long as climate data has been collected—for nearly two centuries. The need for research correlating specific emissions to public health issues might seem obvious—after all, while the causes of pollution inequity have gone uninvestigated, pollution’s inequitable health impacts have been theorized for as long as we have known pollution to be detrimental to health. However, as Rao acknowledged, there has been a historical lack of research in this field. “In science, you can only ask the questions you can answer, and this fell through the cracks of intersection boundaries,” Rao said.

Prior to this study, Rao, as a footprinting climatologist, lacked the tools to link emissions to health markers, such as respiratory illnesses and premature mortality. Similarly, those working on the health impacts of emissions did not have the tools to understand the spatial distribution of atmospheric pollution according to location and consumption of fuels and technologies. While many climate researchers have thought about linking these two areas, the fact that separate tools are involved in creating each model meant there was previously no way to pursue the connection. Rao’s novel insight was to devise an analytical framework where the results from the emissions contribution model would provide data to fuel the health and socioeconomic impacts model, and vice versa. 

The linked contribution and impact model Rao’s team created was a culmination of many smaller models with different purposes, each exchanging information with the others. Rao worked on the aspect of the model that linked spatial distributions of “point sources”—people and industries—across a region to the emissions from that region. His team had a good understanding of point sources’ emission generation patterns, including the usage of fuels involved in transportation, heating, or making food in cook stoves, and those that were indirectly wasteful, such as generating food waste and running electricity. 

Once his team localized emissions to these point sources, an atmospheric model was implemented to reflect realistic weather patterns, including air flows and temperature changes, and deduce the ultimate stabilized concentrations of pollutants. Finally, an impact model linked the pollutant concentrations to individual exposure and mortality, demarcated by age, sex, socioeconomic status, and proximity to urban centers. 

The impact model also mapped the socioeconomic characteristics of people and inferred their future energy demands; for example, rising disposable income could mean that individuals would buy more polluting technologies, such as new fridges or cars, or less polluting technologies, such as gas stoves instead of biomass stoves. These results would in turn provide feedback to the emissions model. Thus, the cyclical nature of the model pipeline ensured that both the emissions and health impacts could be modulated over time.

Not only was the model predictive over time, but it was also highly generalizable across global regions. “You can change out the data, and you’d represent a different part of the world,” Rao said. Since the underlying algorithm remained the same, it was simply a matter of “plugging in” different data points—adding or removing emission-causing technology contributions, changing the population distribution, changing the atmospheric characteristics—and “chugging” to customize the model for any region. 

The team chose to look at India as the first application of the model because India has a mix of income levels and polluting technologies that makes the source and extent of pollution unclear. The model provided clear evidence for what might have been superficially obvious: poorer households in India disproportionately face the impacts of pollution. The pollution inequity is jarring—in fact, the poorest decile of the population in the country faces a mortality risk that is nine times greater than that of the richest decile in the country. 

More importantly, the model highlighted the exact sources of pollution that were causing families of lower socioeconomic status to suffer premature mortality. The most lethal sources of pollutant emissions in India are biomass-burning cook stoves, which cause indoor air pollution and are primarily used by poorer, rural Indian families who cannot afford liquid petroleum gas stoves—the typical choice for richer, urban-based families. According to Rao, pollution from cook stoves leads to nearly one million deaths of Indian babies and mothers every year. 

Moreover, the ambient air pollution that is produced by public services such as transportation and electricity generation far exceeds any benefits these families receive from these services. While they do not consume electricity or use transportation to the same magnitude as richer families, poorer families face asymmetrically exaggerated mortality risks.  

The Role of Government

Climate researchers and public health officials alike have recognized that this grim narrative of inequity in pollution-attributed mortality cannot continue. What policies can be passed to address this disparity? 

In Rao’s ideal world, addressing pollution in its totality and switching from pollution-causing fossil fuels to clean energy within the next ten years is imperative. “Biomass cook stoves need to go away, since the health impacts of indoor air pollution completely dwarf the ambient air pollution,” Rao said. However, poorer Indian households wouldn’t be able to afford and reliably use clean fuels unless the government provided it to them.

The government has taken a necessary first step. “In the past decade, aggressive policies have provided a free stove and a free gas cylinder to fifty million households in India,” Rao said. “The problem is, the fuel has continued to be expensive, so they haven’t used those new stoves as much. It’s just a governance failure: we need to make sure that the fuel is cheap.” He acknowledged that some policies could cause market failures or require public investments. But since poorer people suffer most from the exorbitant price of clean fuels, the onus to provide cheap, clean fuel is on the government. 

According to Rao, one of the more feasible solutions is to use targeted emissions policies, where the costs of emission are apportioned to the consumers of fuels. This would incentivize lower fuel usage and in turn decrease ambient air pollution. 

The proposals don’t stop there. “We need to address food waste and garbage disposal in cities and areas that are affluent, where most of the consumption waste is coming from. We need to create the policy instruments for the costs to flow to the right people,” Rao said. Such policies, along with governments ensuring that clean fuels are accessible to poorer households, could reduce exposure to air pollutants. 

By providing free stoves to a significant proportion of India’s population, the Indian government has shown that it has the capacity to provide clean energy to poorer households. It also seems like it has the capacity to implement targeted emissions policies. 

But capability doesn’t always translate to action. “Unfortunately, the cliche is that there needs to be strong political support for it. There is a cost that has to be paid,” Rao said. And according to him, that is not something that scientific research alone can repair. “Understanding people’s dependence on the fuels, the nature of the lack of reliability of the fuel supply, and the political economy of the fuel price setting and subsidies are essential,” he said. 

Because of the results of the model, scientists now know the contributors and victims of pollution, both geographically and in terms of socioeconomic characteristics. For meaningful change to occur, governments and the public must also internalize these findings. Rao’s current personal goal is to improve global understanding of how to diffuse clean fuels and sustainable energy technologies fast and wide. Accordingly, he joins the gamut of an increasing force of researchers, who by writing policy reports, publishing academic papers, and making data available to non-governmental organizations, are increasingly influencing governmental decisions. 

“I like to think of myself as an academic activist, as having the privilege of generating [scientific] insights,” he said. “I see it as an obligation on my part to make those insights available as broadly as possible.” 

Clearly, “solving climate change” or “fixing pollution” is much easier said than done. Even though the technology to reduce emissions exists, its equitable implementation remains a challenge. Nevertheless, Rao and his team shed some much-needed light on the social ramifications of pollution inequity and mortality. Their work points to targeted emissions policies and biomass cook stove replacement policies as necessary, even inevitable, solutions. 

As scientists and climatologists continue to embrace their roles as policy influencers and activists, governmental inaction will no longer remain an option. In this way, Rao’s ideal world—one in which pollution inequity is vanquished—just might become a reality.

Further Reading:

Rao, N. D., Kiesewetter, G., Min, J., Pachauri, S., Wagner, F. (2021). Household contributions to and impacts from air pollution in India. Nature Sustainability, 4(10), 859–867.