Air pollution from agricultural fires increases hypertension risk

In many parts of the developing world, farmers widely use deliberate fires to burn vegetation and clear land to plant crops. These agricultural fires, however, are known to be associated with health costs due to increased air pollution. We contribute to underpinning the associated health cost estimates by studying the effects of these fires on hypertension risk. Despite being one of the leading causes of mortality globally, there is little direct evidence on how hypertension risk changes with exposure to pollution from agricultural fires. To overcome common data and empirical challenges in this setting, we match blood pressure readings from nearly 784,000 individuals across India with satellite data on 1.2 million agricultural fires, wind direction realizations, and local ambient air pollution. We find that the incidence of hypertension increases by 1.8% for each standard deviation increase in the number of upwind fires observed one day before the blood pressure readings. We find that the impact is stronger among older males, smokers, individuals that were already on blood pressure medication, and individuals belonging to socially marginalized groups. Our estimates suggest that agricultural fires in India lead to hypertension-related additional mortality, associated with USD 9 billion annually in costs.