A four-year, multi-country trial measuring health impacts of reduced indoor air pollution due to the shifting of households from biomass to Liquefied Petroleum Gas (LPG) has yielded  mixed results – defying expectations that reduced indoor air pollution would yield significant health benefits.

The study of 3,200 households in four Asian, African and Latin America countries showed that while the exposure to indoor smoke fell, the expected health gains did not follow.

Despite improvements in air quality so that two-thirds of the households met WHO’s Interim Target 1 for household air pollution, the incidence of severe pneumonia among infants up to one-year “did not differ significantly” when compared to infants in those households that continued to use biomass, investigators with the Household Air Pollution Intervention Network (HAPIN), found.

Nor did the birthweight of newborns rise significantly or incidence  of stunting at 12 months decline – two other early childhood health impacts associated with poor household air quality.

WHO Interim Targets 1 (35 µg/m3) and 2 (25 µg/m3) offer milestones for countries aiming to reduce high household air pollution levels, on the way to the recommended guideline level of 5 µg/m3 of PM2.5.

“Everybody kind of expected on the basis of observational studies that now we’re going to see some health benefits from this, even though, you know, a few other experimental studies were saying, well, we’re not seeing it,” Thomas Clasen, the trial’s principal investigator told Health Policy Watch. “So, people are really scratching their heads.” He is an epidemiologist and professor at Emory University.

This also raises a core policy question: should countries push ahead with fossil fuel-heavy LPG or should they instead leapfrog to electric cooking powered by renewable energy like solar?

The HAPIN trial was launched in 2017 and followed 800 pregnant women, 120 older adult women, and 800 infants in poor communities dependent on solid fuels across Guatemala, India, Peru, and Rwanda. One half of the 3200 households were provided access to LPG for 18 months and results were monitored. The trial was funded by the National Institutes of Health (NIH) and the Gates Foundation, among others.

Mix of positive and negative results

The results showed a mix of positive and negative outcomes.

“Intervention households used LPG exclusively 99.99% of the time,” said Kalpana Balakrishnan of Sri Ramachandra Institute of Higher Education and Research who led the India-leg of the trial. “That answered the question that if you remove the economic barrier, households are willing and able to use a clean energy source, i.e LPG exclusively,” she said.

Average air pollution concentrations in two-thirds of the LPG households declined by half or more – less than 35 µg/m3 (micrograms per cubic meter), Clasen said. The control group that did not use LPG had household air pollution hovering around 70 µg/m3.

“All the health improvements that we expected to see in the intervention compared to the control we did not see,” Balakrishnan told HPW.

Muddying the debate over fuel switching

The World Health Organization (WHO) has also avidly promoted LPG as a clean cooking fuel alternative – despite its climate impacts as a fossil fuel, derived from oil and gas production. These trial results now muddy the debate over whether LPG is still the best option as an “interim” clean fuel choice – or whether countries would be better off promoting electric cooking and heating options, which could reduce indoor emissions even more if they were powered by renewables – and not oil or coal generation.

WHO, for its part, says that the issue will surely be a hot topic of discussion at a major upcoming meeting on air pollution – the Second Global Conference on Air Quality and Health, scheduled for 25-29 March in Cartagena, Colombia.

“WHO is currently reviewing the results from the HAPIN trial and will integrate such evidence in the guidance and support we provide to countries to protect health from household air pollution,” Heather Adair-Rohani who leads the work on air quality, energy and health at WHO headquarters in Geneva told Health Policy Watch in an email response.

“How best to use the results of HAPIN and other key studies to inform decision-making on household energy will be key topic at the upcoming second WHO global conference on air pollution, where WHO, in cooperation with the government of Colombia is calling on countries, cities and organizations to work together to cut the health impacts from air pollution in half by 2040,” she added.

The curious case of lack of health gains despite reduced air pollution 

WHO estimates that around 2.1 billion people worldwide cook on open fires or inefficient stoves that use either kerosene, biomass or coal. Household air pollution was linked to 3.2 million deaths per year in 2020.

And while poor air quality is linked to worsening health, improving air quality in the HAPIN trial did not translate to improved health gains.

The researchers have one key hypothesis as to why.

“In a community where you have multi-dimensional poverty, if you give a clean fuel intervention for a short time, you may not be in a position to pick up the health benefits that result from it,” Balakrishnan said.

“What you need is to follow them up for a much longer period of time where they continue to use LPG,” she added.

Balakrishnan continued, “The way we have to approach this, … in these poor households, you need a package of interventions to achieve improvement in health.”

Clasen too agreed, “We have to say, well, maybe this isn’t going to be enough by itself to achieve the benefits, the health benefits that you were after.”

Households with the biggest declines in air pollution did see some benefits

One other striking factor is that a small set of households with the biggest concentrations of air pollution before the trial, and thus the biggest declines in pollution from the shift to LPG  – did experience more measurable health impacts.

That could suggest that reductions in air pollution that are larger and more dramatic in order yield more measurable health impacts, at least short term.

“When we look at the folks who had the biggest reductions in exposure, it does look like they’ve benefited…at least reductions in PM, 2.5 and black carbon,” Clasen said.

However, at the lower end of the household air pollution scale, the precise relationship between pollution declines and improvement in health benefits – the so-called “dose-response curve” are not yet well defined, Clasen added

“We do not have well-populated dose-response curves for HAP and [health] outcomes,” he said. “So we cannot rule out health benefits that might have been gained at very low levels of exposure.”

But practically speaking, it’s going to be very difficult to push household concentrations further down in many low-income settings when other environmental and cultural factors such as high rates of smoking, as well as high levels of outdoor air pollution also come into play, he added.

“It’s unlikely that any programmatically delivered HAP intervention is going to achieve lower levels of exposure than what we achieved here, when we had the benefit of free stoves and fuel – and thus nearly exclusive LPG adoption. So from a practical standpoint, we are not likely to improve these health endpoints by getting householders to lower levels of exposure than what we achieved in the trial.”

What do these results mean for policy?

Regardless of the mixed outcomes, Clasen stressed that the results should not be read as a signal to put brakes on transitioning to LPG in developing countries.

Even if switching to LPG does not lead to expected health gains in the short run, it still is a significantly efficient fuel. It also lowers greenhouse gas emissions compared to biomass and thus has climate benefits apart from reducing the drudgery involved for women.

LPG’s positive impact on women

“When you’re cooking over a chulha (earthen stove), the drudgery from collecting the firewood or the coal or the gobar (cowdung) to prepare the chulha versus cooking on an LPG…the time it takes…there’s also an opportunity loss because of the time that’s lost in cooking and working around it,” said Neha Saigal, Director of the Gender and Climate Change programme with India-based Asar Social Impact Advisors. Women in the communities Asar works with expressed willingness to use LPG when it was an affordable option.

Cooking on a traditional stove using biomass or coal also directly exposes women to even higher levels of air pollution than might be measured as ambient indoor levels, Saigal said. So shifting may have other health benefits that weren’t captured yet by the HAPIN trial.

Beyond LPG: Staring at limited options

LPG is increasingly affordable and accessible in many developing countries. India, the world’s most populous country, has made tremendous gains in improving LPG access among poor and rural communities though gaps remain. Around 99.8% households in the country now have access to LPG for cooking, according to government data from the year 2021.

And while LPG is a fossil fuel, it is significantly cleaner than biomass. Alternatives to LPG are either not efficient enough for everyday and reliable use, like solar, or require reliable electricity.

Clasen has two reservations about promoting electricity for household cooking in developing countries right now. “One is, is electricity going to do any better than LPG? Right, number two is that [the] electricity is usually generated using fossil fuels, so we may not actually be reducing the climate load by transitioning to electricity unless we also can figure out how to do it renewably,” he said.

Other experts said the quest for better solutions should nonetheless continue.

“I don’t see any other solution at this point of time, at scale other than LPG. But yes, there’s a lot of scope to demonstrate, to pilot with electric cooking, to come up with better chulhas that don’t give out smoke…solar cook stoves,” Saigal of Asar said. “But if we want to support women at the moment, we should make LPG available to them, because that is the thing that’s available now in the market,” she added.

Balakrishnan also raises an ethical question – the poor should not bear the burden of waiting to transition to electric cooking when it is not the norm in urban and well off households. Given that LPG is a viable near-term clean energy choice, the poor too should have access to it right away, she said.

Continuing long-term research will yield more answers 

For now, the HAPIN trial continues to follow children in three locations – Guatemala, India and Rwanda – until they reach the age of five. They want to see if delivering their mothers LPG access for 18 months has had any long-term health benefits that might become clear only later, like neurocognitive development or development of a child’s mental abilities.

“It could be quite compelling from a policymaker standpoint,” Clasen said.

Image Credits: WHO/Adobe Stock/Dennis Wegewijs, WHO, Guatemala HAPIN team, T20 Policy Brief, July 2023, India HAPIN team.