The results of a recent study suggest that four of the most widely-used cookstoves in Mexico may pose a lower risk to human health than previously thought. Contradicting previous assumptions, the study found that the four most common models of chimney plancha cookstoves would likely meet WHO’s indoor air quality interim targets for fine particulate matter (PM2.5) and carbon monoxide (CO).

In the past, it’s been assumed that stoves with chimneys, which are common in Latin America, do not meet WHO indoor air quality guidelines because of emissions that escape from the stove into the kitchen, also known as fugitive emissions. Previous studies have estimated that approximately 25% of total PM2.5 emissions from chimney stoves ended up in the kitchen, leading to higher estimates of risk for a range of respiratory illnesses and cardiovascular disease.

Researchers from the Laboratorio de Innovación y Evaluación de Esufas de Biomasa (LINEB) used a double-hood setup to simultaneously measure chimney emissions and fugitive emissions. They found that fugitive emissions comprised 3-7% of total PM2.5 emissions and 1-2% of total CO emissions. This data, combined with field measurements of kitchen characteristics, was used to model kitchen concentrations of pollutants. Based on this modeling, the chimney stoves would meet WHO’s indoor air quality interim targets for PM2.5 in 94-99% of cases, and the 24-hour CO guidelines in 100% of cases.

Given the findings, researchers and implementers interested in health impacts could consider chimney stoves and chimney stove maintenance as an interim solution that does not require a fuel change in regions where chimney stoves are commonly in use and available models have low fugitive emissions, like those included in this study.

While improving indoor air quality is important for health in the household, these stoves still contribute to ambient air pollution and therefore still have broader negative impacts. Additional research is necessary to verify performance and concentrations in the field and to fully understand the extent of re-infiltration of externally vented emissions back into households.

This research was funded through an Alliance-sponsored grant. Follow-up research work is being conducted to measure how much of the chimney emissions re-infiltrate the households and how far apart homes need to be to ensure that the indoor air quality benefits of chimney stoves are received.