Quantifying the Potential Health Impacts of Unvented Combustion in Homes – A Meta-Analysis

While a growing body of scientific literature describes the population health impacts of fossil fuel production and burning via climate and air pollution pathways, less is known about the health impacts of indoor combustion. This paper summarizes the results of studies from the last two decades that investigated the association between exposure to sources of unvented combustion pollutants in homes and a range of health outcomes. We found gas combustion to be associated with 6-28% (95% confidence intervals) increased odds of asthma symptoms, 4-51% increased odds of systemic symptoms, 7-81% increased odds of asthma medication use, and 3-12% increased risk of mortality. These findings can be used to improve public health, for example, by informing requirements for improved ventilation and source control, justifying switching to vented appliances, better regulation of device emissions and quantifying the benefits of electrification of end-uses. Dose-response relationships between human health, NO2 exposure, and other by-products of combustion are not characterized with a high degree of precision. However, there is clear evidence of a wide range of health effects, even at low levels of exposure. Despite the various designs, geographic sites, length of follow-up, and study dates, we noted a level of consistency between the studies within the current meta-analysis, and with previous ones, which strengthens the level of confidence in our findings.