Abstract Description: Historically, power plants have been major contributors to poor air quality in the United States and greenhouse gas emission. Power plant emissions have increased and decreased since the early 1900s because of factors such as environmental legislation, electricity demand, and available fuels. The objective of this project is to quantify and characterize the variation in emissions and exposure from power plants in the United States from 1940 to 2020. For periods without direct measurements, we estimate SO₂, NOx, PM, Hg, and CO₂ emissions using emission factors derived from existing US power plants. These estimates consider operating capacity and installed emissions control technologies at individual electricity generating units. The emission factors are calculated based on fuel types and facility unit characteristics. We use reduced complexity atmospheric models including the HYSPLIT average dispersion (HyADS) model and the Intervention Model for Air Pollution (InMAP), to quantify PM2.5 concentrations attributable to power plant emissions. Our analysis explores how these emissions and exposures have evolved over time, and we will associate the changes with legislation and fuel use. SO₂ emissions, 90% of which originated from coal power plants primarily located in the Midwest and the West, surged by 545% from 1940 to their peak in 1970, followed by a 10% decline from 1970 to 1990. Between 1995 and 2020, SO₂ emissions further plummeted by 93%, with the most significant reductions occurring between 2005 and 2012. Similarly, NOx emissions experienced a dramatic increase of approximately 1117% from 1940 to 1990 but subsequently decreased by 87% from 1995 to 2020, exhibiting a steady decline during the 2005-2012 period. In contrast, CO₂ emissions saw a more gradual decrease of 22% during this period, highlighting the ongoing need for targeted efforts to mitigate greenhouse gas emissions from the 20th to the 21st century. These reductions can be attributed to key regulations aimed at reducing air pollution and costs of fuel. Programs implemented for SO₂ and NOx, utilizing various control technologies and fuel switches significantly decreased emissions. However, the modest 22% reduction in CO₂ emissions underscores the continued need for focused regulatory efforts and initiatives to achieve further reductions in greenhouse gas emissions.
