Environmental disasters and birth outcomes: impact of a tailings dam breakage in Brazil

There is evidence of a relationship between in utero exposure to catastrophic events and adverse birth outcomes, usually attributed to heightened maternal stress. The objective of our work was to evaluate if the breakage of a dam containing wastefrom a mining cite in Brazil, in 2015, an environmental disaster popularly known as the Mariana Tragedy, affected the health of newborns exposed in utero. We used administrative data on birth records and reports on the Mariana Tragedy to identify all births from newborns exposed in utero and the intensity of that exposure, according to the mother's municipality of residence. Using a difference-in-differences framework, we estimated the impact of different intensities of exposure on birth outcomes. We found that being directly exposed in utero to the Tragedy resulted in 1.86 days shorter gestational age and 2.6 percentage points higher incidence of preterm birth (<37 weeks). We found no impact on birthweight related outcomes. The effect is larger than previously identified for other catastrophic events. We hypothesize that this is probably due to the Tragedy impacting birth outcomes not exclusively through heightened maternal stress, but also through depressed economic activity in directly affected municipalities.