Political Drivers of Air Pollution in the U.S.: A Time-Series Analysis (1959-1998)
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Presentation at the 5th International Conference on Environmental Science and Technology, organized by the American Academy of Sciences, in 2010. Abstract: This study tests the effect of environmental movement actions, political opportunities, policy and its implementation, and media attention on air pollution in a time-series analysis (1959-1998). It examines changes in national emissions of 5 types of air pollution: Sulfur Dioxide, Carbon Monoxide, and Volatile Organic Compounds (combined into an index with Cronbach’s Alpha = 0.904); Nitrogen Oxides (NOx); and Particulate Matter smaller than 10 micrometers (PM-10). The data were first-differenced to correct for non-stationarity, Multiple OLS Regression was used to determine the direct influence of political processes on air pollution (controlling for economics). Multiple interactions between movement effects, the media, and political opportunities were also investigated in additional OLS regressions. Results show that media attention to the environment is an important predictor of all 3 dependent variables. Additionally, the environmental social movement is only effective given specific political opportunities, namely Democratic Party control of the federal government, media attention to environmental issues, and effective policy. These interactions are specific to the type of air pollution and not generalizeable across pollutants. The environmental movement also only appears to be effective at combating highly visible pollutants that are on the political agenda, since NOx and PM-10 are both more politically visible than the other three types of air pollution. The study demonstrates the complexity of air pollution, the importance of media attention, and the limited impact of the environmental movement on real-world outcomes.
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Political Drivers of Air Pollution in the U.S.: A Time-Series Analysis (1959-1998)
- 1. Political Drivers of Air Pollution in the U.S.: A Time-Series Analysis (1959-1998) A.C. McCreery The Ohio State University
- 13. Results: Index of SO 2 CO & VOCs n = 38 *** p < 0.001, ** p < 0.01, * p < 0.05; one-tailed 1.705 Durbin-Watson D-statistic 0.110 Adjusted R-squared -6.106 Constant 3.72 E-03 Movement Actions 0.320 Implementation Funding -3.64 E-03 Air Pollution Policy -6.18 E-04 * Media Attention (Logged) -1.66 E-02 Corporate Taxes 9.79 E-04 Congressional Hearings (Logged) -0.073 Democratic Unity -276384 Real GDP / Capita, squared 153.90 Real GDP / capita Coefficient Base Variables
- 14. Results: NO x n = 38 *** p < 0.001, ** p < 0.01, * p < 0.05; one-tailed 1.618 Durbin-Watson D-statistic 0.470 Adjusted R-squared -1.436 Constant 1.88 E-03 Movement Actions 0.080 Implementation Funding -3.93 E-03 Air Pollution Policy -2.05 E-04 * Media Attention (Logged) 1.16 E-03 Corporate Taxes 5.94 E-04 Congressional Hearings (Logged) -0.038 Democratic Unity ** GDP & GDP squared F-Test for joint significance (P > F) -207073 ** Real GDP / Capita, squared 102.45 * Real GDP / capita Coefficient Base Variables
- 15. Results: NO x Interactions *** p < 0.001, ** p < 0.01, * p < 0.05; one-tailed aaa p < 0.001, aa p < 0.01, a p < 0.05; two-tailed. 0.512 0.560 Adjusted R 2 -5.18 E-02 Democratic Unity 1.44 E-03 a Movement Actions -2.51 E-03 * Movement actions * Democratic Unity -3.04 E-03 Air Pollution Policy 2.15 E-03 aa Movement Actions -4.30 E-04 ** Movement actions * Air Pollution Policy Coef. Main Effects Coef. Interaction Variable
- 16. NO x Explanatory Power
- 17. Results: PM-10 n = 38 *** p < 0.001, ** p < 0.01, * p < 0.05; one-tailed 1.762 Durbin-Watson D-statistic 0.198 Adjusted R-squared -3.555 * Constant 5.96 E-04 Movement Actions 0.184 Implementation Funding -4.40 E-03 Air Pollution Policy -1.96 E-04 * Media Attention (Logged) 8.81 E-04 Corporate Taxes 2.55 E-04 Congressional Hearings (Logged) 0.030 Democratic Unity GDP & GDP squared F-Test for joint significance (P > F) -134973 * Real GDP / Capita, squared 60.92 Real GDP / capita Coefficient Base Variables
- 18. Results: PM-10 Interactions *** p < 0.001, ** p < 0.01, * p < 0.05; one-tailed 0.330 Adjusted R 2 -4.85 E-05 Media Attention 1.12 E-03 Movement Actions -7.09 E-06 ** Movement actions * Media Attention Coef. Main Effects Coef. Interaction Variable
- 20. Significant Effects Media Attention Air Pollution Policy Environmental Movement Actions Democratic Unity NO x Emissions - - + +
- 21. Significant Effects Media Attention Environmental Movement Actions PM-10 Emissions - Index Emissions (SO 2 , CO, &VOCs) Media Attention -
- 23. Acknowledgements Dr. Robert Brulle Dr. Jon Agnone Dr. J. Craig Jenkins Colleagues The Fay Graduate Fellowship Fund in Environmental Sciences NSF Grant #SES-0455215, “Civil Society & the Environment” Ohio State University Environmental Science Graduate Program Ohio State University Dept. of Sociology Funding & Resources
Editor's Notes
- -Previous research has addresses the effect of policy such as the Clean Air Act, and although it is not conclusive it does imply that policy can reduce air pollutant emissions. -Previous research has also addressed the influence of economic growth on air pollution, and this study will control for economic effects. -This study contributes to the literature by addressing other factors, specifically the role of the environmental movement (either directly or indirectly) and the effect of political agenda setting through media attention to the environment. -Additionally, many previous studies have focused on only two type of air pollution, whereas this study includes 5 pollutants, taking a more comprehensive look at air pollution.
- -Air pollution is measured using 5 of the 6 criteria air pollutants regulated by the EPA. -SO2, CO, and VOCs are combined into an index because they follow a very similar pattern over time. The index has a surprisingly high Cronbach’s alpha, which indicates that those 3 pollutants are very closely correlated and analyzing them in an index is statistically sound. It also implies a possible theoretical connection, and could indicate similar driving factors. -The other 2 measures of air pollution are NOx and PM-10, and data for all 5 are provided by the EPA. Note: the analysis runs from 1959-1998, and the length of time is constrained by data availability.
- -The 3 measures of air pollution included in this study following different patterns over time, and this graph shows those patterns of variation around the mean. The index rises until around 1970 when the EPA was created, and then declines after that. NOx rises and then plateaus at around 1980. Interestingly, during the 1980’s there were some significant rollbacks in enforcement of the Clean Air Act. PM-10 mostly declines throughout this time period, until it reaches a threshold and plateaus in the mid 1980’s.
- -Environmental movement actions include a variety of tactics such as protests, letter writing campaigns, lobbying, litigation, and these are hypothesized to reduce air pollution. Environmental movement actions were coded from the NYT Index. -Political opportunities for the movement enable more effective action to be taken. Political opportunities include the presence of elite political allies, and a weaker opposition. Allies are measured as a dummy variable: 1 when Democrats control the three branches of the federal government, and 0 in all other years. Strength of business interests is measured by proxy, as the proportion of federal tax revenues that are paid by corporations. Higher tax revenues from corporations should indicate that they hold less political power and are thus less able to influence environmental regulation, so a negative relationship between corporate taxes and air pollution is hypothesized.
- -Political Agenda Setting refers to the fact that some issues are considered to be more important than others and different times. If an issue is on the political agenda then public attention is focused on that issue and politicians tend to take action to address it. -The environment can be placed on the political agenda by media attention, and Congressional hearings on the environment are indicators that it is on the political agenda and act as political openings. -Places an issue on the political agenda grants it legitimacy and salience, which increases the likelihood of political action on that issue. -Thus media attention to the environment and congressional hearings on the environment are both hypothesized to lower air pollutant emissions. -Media attention is measured by magazine articles on the environment that are listed in the Reader’s Guide to Periodical Literature. -Congressional hearings on the environment were coded by the Policy Agendas Project.
- -Previous research is not conclusive because it has not distinguished between effective versus symbolic policy. Symbolic policy can make politicians look like they’re doing something without having any real-world effects. Policy on Air Pollution could be a mixture of effective and symbolic policy, so it is important to measure the quality of air pollution policy to determine its effects. -Implementation of policy could help explain earlier mixed results since even effective policy that is poorly funded or poorly implemented is unlikely to have beneficial results. -In addition, policy or Implementation could also interact with other variables such as the environmental movement, and these interactions will be tested for as well. -Stronger air pollution policy and more effective implementation are hypothesized to reduce air pollutant emissions. -Implementation was measured based on the EPA budget, and prior to 1970 it was based on money earmarked into air pollution legislation.
- I have constructed a unique measure for the strength of air pollution policy, and it’s worth describing in more detail.
- However, results that so show are strengthened by the fact that the model is very conservative. Additionally, coefficients are very small due to first-differencing, but this is a mathematically induced constraint and does not indicate a small effect
- Real gross domestic product is included to control for linear or quadratic economic effects, but I won’t be discussing those today because it has been well-studied in previous literature. The only significant effect for the index is media attention.
- Media attention also has a significant negative impact on NOx emissions.
- There are two significant interaction effects for NOx, and these seem to support the theory of political opportunities for the environmental movement. The adjusted r-squared for the model including either one of the interactions is higher than the adjusted r-squared of the base model alone (which was 0.47). (skip to next slide quickly)
- Showing the increase in adjusted r-squared graphically, this indicates that the models including one of the interactions has greater explanatory power than the model without the interaction.
- The effect of media attention is the only consistently influential factor across all three measures of air pollution, support the theory of political agenda-setting.
- Note: Similar to NOx, the adjusted r-squared for the interaction is much higher than the base model alone (which was 0.198). So the model PM-10 with the interaction also greater explanatory power than the model without the interaction. For PM-10, media attention has a direct effect, but it explains more of the variation in PM-10 emissions when interacting with movement activity.
- In fact, the explanatory power of the model including the interacting is more than 1.5 times the explanatory power of the base model.
- -Overall, the environmental movement has a significant negative influence on NOx emissions when interacting with either democratic unity or air pollution policy. (I.e. the interactions are significant, as are the movement effects in the interaction models). -Media attention also has a direct effect.
- For PM-10, the combined influence of environmental movement actions and media attention has greater explanatory power than media attention alone. When the interaction is included in the model, the interaction effect is significant but the two factors individually are not, indicating a truly combined effect.
- The only consistently influential factor was media attention to the environment, which provides strong support for the importance of setting the political agenda. Media attention brings environmental problems to the attention of the public and policy-makers, which helps reduce emissions. The mechanism for this effect has not yet been explored, but is worth pursuing in future research. The environmental movement was effective at reducing 2 of the three measures of air pollution, but only under specific conditions. Political opportunities appear to be very important in helping the environmental movement achieve at least some of its goals. Finally, it is clear from these results that air pollution cannot be treated as a homogenous concept when examining social or political drivers. Theories of social impact on the environment sometimes assume generalizability across different pollutants, but even looking only at air pollution the results are not generalizeable. This holds true for both economic and political factors, and social theories of environmental impact must address the differences between various types of impact in order to remain empirically useful.