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When water is below normal levels in Latin America, it's not just farmers and consumers who suffer. A new study finds that air pollution spikes, and thousands of people die prematurely as a result.

The paper, "" was published in Nature Communications, one of the world's leading scientific journals. The study shows that the culprit of increased air pollution isn't dust storms or wildfires, but something far more mundane: the way electricity is generated when the rain stops.

Hydropower supplies about half of the electricity in Latin America and the Caribbean (LAC). The rest comes mostly from combustion plants fueled by coal, oil, gas, or biomass. Hydropower depends on steady river flows, which droughts can interrupt.

When dams run dry, the region turns to its backup power sources, like fossil fuel and biomass plants, to fill the gap. These plants release fine particulate matter (PMâ‚‚.â‚…), tiny airborne particles that can lodge deep in the lungs and cause heart and respiratory diseases.

The research was led by Mathilda Eriksson and Alejandro del Valle, of the M.R. Greenberg School of Risk Science at Georgia State's Robinson College of Business, along with Alejandro de la Fuente of the World Bank. They set out to determine how much droughts increase PMâ‚‚.â‚… pollution in Latin America, and how many lives it costs.

Drawing on 20 years of monthly data from more than 3,000 power plants, the team tracked drought conditions in hydropower watersheds and PM₂.₅ levels around combustion plants. They found a clear pattern: When hydropower in a region is limited by drought, power generation moves to combustion plants, and PM₂.₅ levels near these plants rise on average by 0.83 micrograms per cubic meter (μg/m³), which is a large jump in places already well above the World Health Organization's guideline of 5 μg/m³.

The study estimates that drought-related shifts to combustion power plants cause between 3,700 and 10,600 premature deaths each year in the region, translating to $4.2–12.2 billion dollars in annual economic losses. Over the 2000–2020 period, cumulative losses reached about $150 billion dollars.

"The human toll is staggering. In Latin America, 443 million people live within 50 kilometers of a power plant, so these are heavily exposed population areas experiencing negative health impacts of this air pollution," said co-author Alejandro del Valle. "On top of that, four out of five combustion plants are located near communities with lower-than-average United Nations Human Development Index scores, meaning poorer and more vulnerable populations bear the brunt of the pollution."

A worsening problem

Climate models suggest the problem will only grow. Between 2020 and 2059, most of LAC is expected to see a 22–24% increase in drought exposure for hydropower plants. In a worst-case scenario with no retirement of combustion plants and high climate forcing, annual premature deaths could hit 30,000 per year by 2059.

Even in more optimistic climate scenarios, the study warns, health risks will persist unless energy policy changes. That's because climate change isn't the only driver—population growth, economic development, and the slow pace of plant retirement all play roles.

Solving the problem

The research shines a light on a hidden cost of drought: public health damage from air pollution. Crucially, the study cautions that simply adding more solar and wind power won't solve the problem if polluting backup plants remain the go-to option in dry years. So, what can be done?

"Our demand for electricity is only going to increase, and what is happening now with these plants has a major human and economic cost, but there are things lawmakers can invest in now that will ultimately be cost-effective and save lives," said del Valle.

For policymakers, the findings are a call to act on multiple fronts.

• Build energy storage so clean power can be deployed even when hydropower is offline.
• Expand regional electricity trade with aligned pollution standards to avoid shifting emissions across borders.
• Target plant retirements in vulnerable communities to advance environmental justice.
• Encourage demand-side management—such as conservation incentives—during drought periods.

"Building energy storage capacity and regional electricity trade are two clear alternatives that can be implemented now to reduce reliance on harmful combustion plants," said del Valle. "As these investments are made, combustion plants that are closest to large populations of disadvantaged people should be retired first, and our paper offers a road map for identifying the worst offenders."

del Valle notes the problem isn't limited to Latin America. Similar studies have been conducted looking at the environmental costs of electricity generation in the U.S. And as droughts intensify in a warming world, the health of millions may depend on how quickly these hydropower-reliant regions can break the cycle of dry rivers, dirty air, and premature death.