The Impact of Three Recent Coal-fired Power Plant Closings on Pittsburgh Air Quality: A Natural Experiment Open Access

Russell, Marie C. (2015)

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Background: The region of southwestern Pennsylvania, including the metropolitan Pittsburgh area, suffers from high ambient concentrations of fine particulate matter (PM2.5), relative to other areas in the United States. PM2.5 is known to be associated with adverse respiratory and cardiovascular health impacts.

Purpose: The objective of this study is to evaluate whether the closing of three coal-fired power plants within the southwestern Pennsylvania region resulted in a significant decrease in fine particulate matter concentration.

Methods: Both PM2.5 data obtained from 12 EPA ground stations in the study region, and aerosol optical depth (AOD) data retrieved from the MODIS instrument onboard the Aqua satellite, were used to estimate monthly averages of fine particulate matter concentration from January of 2009 through December of 2014. The significance of each plant shutdown in predicting PM2.5 concentration was evaluated using a generalized linear regression model that controlled for seasonality.

Results: The ground station regression analysis shows that the closing of the Elrama plant in 2012 resulted in a significant decrease of 1.34 μg/m3 in PM2.5 concentration. Although there was a decrease in PM2.5 concentration following the closing of Mitchell and Hatfield's Ferry power plants in 2013, this decrease was not significant at α = 0.05. The satellite data regression analysis shows that both the Elrama closing and the joint closing of the Mitchell and Hatfield's Ferry plants resulted in a significant decrease in AOD: decreases were of 0.021 and 0.013, respectively.

Conclusion: The use of satellite-retrieved AOD data allows for greater spatial coverage than that provided by EPA ground station observations. In this study, the closing of two power plants in October of 2013 significantly decreased AOD levels throughout the study region, but did not significantly lower PM2.5 measured from EPA ground stations. Further analysis is needed to determine how individual ground stations might be influenced by interfering sources of emissions.

Table of Contents

Introduction. 1

1.1 Fine Particulate Matter and its Health Impacts. 1

1.2 PM2.5 in Pittsburgh, PA. 2

1.3 Pittsburgh's Coal Industry: Past and Present. 3

1.4 Using Natural Experiments to Assess Air Quality Improvements. 5

1.5 Study Objectives and Hypotheses. 8

Data and Methods.8

2.1 Study Area. 9

2.2 Remote Sensing Data. 9

2.3 Ground Station Data. 11

2.4 Analysis. 12

2.5 Sub-setting the AOD and PM2.5 Data. 14

Results. 15

3.1 Descriptive Statistics. 15

3.2 ANOVA test results. 16

3.3 Linear Regression Results and Data Subsets. 17

Discussion. 19

4.1 Notable EPA Ground Stations. 19

4.2 Using Satellite-retrieved AOD Measurements to Assess Improvements in Fine Particulate Matter Concentration. 20

4.3 Limitations. 21

Conclusion. 22

References. 23

Tables and Figures. 29

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