Air Pollution Accountability: Assessing Regulatory Impacts on Emissions and Air Quality

by:

Lucas R.F. Henneman

Advisor:

Dr. Armistead G. Russell

Committee Members:

Dr. James A. Mulholland (CEE), Dr. Patricia L. Mokhtarian

(CEE), Dr. Athanasios Nenes (EAS), Dr. Paige E. Tolbert (Emory)

Date & Time: 6 July, 2017 at 11:00 a.m.

Location: Ford Environmental Science & Technology L1-116

ABSTRACT

The United States has seen large improvements in air quality over the last half century with the implementation

of regulations designed to reduce air pollutant emissions. Regulatory costs, estimated by the Environmental

Protection Agency at tens of billions of dollars per year, motivate air pollution accountability research, which

evaluates impacts of air quality regulations on emissions, air quality, exposure/dose, and public health—

components of the so-called Accountability Chain. This work adds to the expanding air pollution accountability

field by investigating a range of regulatory actions on electricity generating units and on-road mobile sources

promulgated since the 1990s. Results show that the United States has seen major emissions reductions over this

period, and most of the decreases are attributable to regulatory policies, although influences such as fuel costs,

demographic shifts, and technological improvements have influenced emissions reductions as well.

The bulk of this work investigates the impacts of changing emissions on air quality in the Eastern United States.

Analyses focus on ambient ozone and particulate matter with diameter less than 2.5 μm (PM2.5), two pollutants

linked with adverse health and environmental impacts. Observation-based statistical models and a deterministic

air quality model (the Community Multiscale Air Quality model—CMAQ) show that emissions reduction

programs reduced the highest ozone concentrations while simultaneously increasing the lowest concentrations.

For PM2.5, controls reduced both the annual mean values and the variability. Meteorology had large impacts on

daily pollutant concentrations, but long-term trends were driven by emissions reductions. An evaluation shows

that CMAQ captured ozone and PM2.5 concentrations and changes over the decade, but the model did not always

get the right answer for the right reasons. For example, the model had trouble estimating absolute concentrations

and variability of certain species that make up PM2.5, but the biases canceled out when the species were summed.

This research provides important evidence that links regulations to emissions reductions and air quality

improvements while accounting for numerous concurrent changes. Lessons learned in accountability research can

be applied to future air quality management strategies, and this work provides two examples: one using empirical

and CMAQ modeling of ozone in the United States, and another using an integrated assessment of energy, air

pollution, and climate policies in South Africa.