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Electricity imports within the U.S. are associated with about 700 premature deaths annually, study finds

When fossil fuel power plants produce electricity, they also emit air pollutants that lead to premature mortality.

Emissions from coal-fired power plants are particularly harmful. Previous studies, as well as a new one from Stanford University, explain that as the U.S. power sector reduces coal-fired power overall, the total number of premature deaths linked to electricity generation is declining. However, the new study reports that air pollution from fossil fuel power plants is still associated with an estimated 4,000 to 9,000 annual premature deaths in the United States.

As the share of variable renewables increases in our electric grids, there may be a need to import more electricity from neighboring regions, (“balancing areas” in power sector parlance), to quickly meet changes in electricity demand. For example, about 20 percent of California’s electricity demand in 2021 was met by importing electricity from other regions. If such imports are performed with electricity generation from coal power plants, (or, to a lesser extent, from natural gas power plants), there may be important impacts in the form of premature mortality. Across the United States, electricity that is generated in one balancing area but then used in another accounts for about 700 premature deaths, according to the Stanford research published in Environmental Research Letters on May 19. The exact number of premature deaths remains uncertain because this estimate relies on models that associate the increase in concentrations of very small particles with health outcomes.  

Nora Hennessy
Stanford doctoral student Nora Hennessy

Electricity that is produced and used in the same balancing area still accounts for about 92 percent of the health consequences. However, in some regions the role of imports is very significant.  More than half of the premature deaths associated with electricity use in most of California and the Northwest occur in other western states that supply electricity to the West Coast.

“Some regions with fairly clean grids – for example lot of wind and solar power – may need to import electricity from areas with a lot of coal-fired power to meet their demand for electricity, but this may be resulting in health damages for people who are not in the region that is being served with that electricity,” said the study’s lead author, Eleanor “Nora” Hennessy, a PhD student in Stanford’s Department of Energy Resources Engineering.

Shifting focus

Research on the health impacts of power production traditionally have focused on where the electricity is generated and how the air pollution travels from there, and regulations have followed that path. The researchers here, however, want to shift some of the focus to where the problematic electricity is being used.

Inez Azevedo
Ines Azevedo, Stanford associate professor

“We need to move towards more sustainable electricity generation, and that means reducing both greenhouse gases that lead to climate change and these other air pollutants that cause premature mortality,” said the study’s senior author, Ines Azevedo, associate professor in Energy Resources Engineering. “To really transition to sustainable electricity systems, we need to look at different dimensions of these systems, and we need to understand the unintended negative consequences choices in one region may induce in other regions.”

“Only then will we be able to implement informed decisions. While we are breathing cleaner air than in previous decades, we still suffer from significant health impacts from air pollution, which include damaged respiratory and cardiovascular systems, heart disease, lung cancer, and strokes,” Azevedo said. “So, we need comprehensive policies that will simultaneously consider climate change, health, affordability, and distributional consequences."

The high number of premature deaths linked to electricity that is consumed in California, Oregon and Washington but generated elsewhere is due primarily to coal power plants in the Southwest and Intermountain West. However, some of these three coastal states are moving their laws and regulations to address this issue. In Washington, a 2019 law bars imports of coal-fired power by 2025. California has the goal of a carbon-free grid by 2045, which probably will result in almost no imports of electricity generated with fossil fuel.

Distribution and transfer of premature mortality caused by imports and self-generation in the most damaging balancing areas.
Distribution and transfer of premature mortality caused by imports and self-generation in the most damaging balancing areas.

U.S. East and Midwest

While West Coast states are exporting health impacts to other western states, states east of the Rocky Mountains tend to keep the health damages from power production within their large regional grids. Electricity use in the regional grid covering much of the U.S. Midwest along with much of Arkansas, Mississippi and Louisiana is linked to more premature deaths than in any other region. This is true for both self-generated power and imports. Self-generation also leads to significant premature deaths within these three balancing areas: Texas; the regional grid covering most of a triangle from New Jersey down to Virginia and up to Chicago; and the grid basically from Oklahoma to North Dakota.

In terms of carbon dioxide, more than half of the emissions behind California’s electricity use are from power produced in other Western states. The state’s own energy is low carbon, but it imports roughly a quarter of its power from states with relatively high CO2 emissions, and thus it may be important to consider the implications of imports in the state’s climate change policy.

“As the grid gets cleaner, the effects of power imports are expected to decrease,” said Hennessy, “but the impacts of electricity imports must be monitored and considered during the energy transition to ensure that people in certain states, or of certain ethnicities or income levels are not forced to bear the burden of an overall low-carbon U.S. electricity system.”

Other authors of the study are Stanford professor Sally Benson and adjunct professor Jacques de Chalendar, PhD ’20.

This work was supported by the Department of Energy Resources Engineering at Stanford University.

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