Indoor Air Pollution Decreasing, But Low-Income Countries Still Bear the Burden

Anoop S.V. Shah, PhD

The public health burden of indoor air pollution is decreasing, but the issue remains a major concern in the poorest regions of the world, according to a new study.

More than one-third of the world’s population (3 billion people) use polluting fuels like wood, coal, crop waste, and animal dung to heat their homes and cook. This translates into indoor air pollution that leads to significant cardiorespiratory, pediatric, and maternal disease among those exposed to the pollution.

The fact that indoor air pollution is dangerous is not a new discovery, but corresponding author Anoop S.V. Shah, PhD, of the London School of Hygiene and Tropical Medicine, wanted to get a more up-to-date picture of the extent to which such indoor pollution continues to burden global public health.

To do so, they conducted a meta-analysis of 476 studies, collectively covering 15.5 million participants from 123 countries. Using that data, they sought to compare the risk of common adverse outcomes due to exposure to indoor air pollution versus the risk of those outcomes absent any exposure to air pollution. Their findings were based on the years 2000-2017.

The investigators found a number of health problems associated with indoor pollution. Among them were asthma (relative risk [RR]: 1.23), acute respiratory infection in adults (1.53) and children (1.39), chronic obstructive pulmonary disease (1.70), lung cancer (1.69) and tuberculosis (1.26). Higher rates of low birth weight, cardiovascular mortality, stillbirth, and other health consequences were also identified, among others. All RRs were calculated with 95% confidence intervals.

In the year 2017, Shah and colleagues concluded, indoor air pollution contributed to 1.8 million deaths and 60.9 million disability-adjusted life-years (DALYs).

However, the impact was disparately spread across the globe; 60.8 million of the 60.9 million DALYs occurring in low- and middle-income countries (LMICs), and just 0.09 million DALYs in high-income countries.

Though the burden of indoor air pollution remained high, it was on the decline. Shah and colleagues found indoor air pollution-related mortality dropped 36% between 2000 and 2017, and pollution-related disease burden dropped by 30%. Again, however, the greatest improvements were seen in high-income countries.

“The burden of disease from household air pollution is almost exclusively borne by LMICs where there is little access to electricity or gas cooking,” Shah and colleagues wrote. “Paradoxically, the greatest relative reduction in burden attributable to household air pollution was observed in Europe where the burden was the lowest.”

The investigators added that some efforts to ameliorate the problem in LMICs might not be having the expected outcomes. They noted that the World Health Organization recommends transitioning from polluting fuels to clean-fuel technology in households that burn fuel to heat their homes or cook. However, Shah and colleagues found that the implementation of biomass-fueled cookstoves, which are billed as cleaner, did not lead to an improvement in outcomes.

Shah and colleagues said their analysis shows that it is important that interventions are put in place, but also that those interventions can be linked with demonstrated improvements in the health of the people they are intended to benefit.

“There is an urgent need for evidence-based policy and decision-making to ensure children and adults living in LMICs have clean air to breathe in their homes,” they said.

The study, "Adverse health effects associated with household air pollution: a systematic review, meta-analysis, and burden estimation study," was published in The Lancet Global Health.