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The abatement of particulate matter 2.5 in Los Angeles County: a counterfactual evaluation

DOI:10.1007/s10668-020-00904-w
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Meng-jieu Chen
Meng-jieu Chen
Meng-jieu Chen
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The ambient PM2.5 concentration in Los Angeles (LA) County has been on a decreasing trend since LA County was designated as a nonattainment area in 2005. However, whether the nonattainment assignment is the underlying cause of the county’s reductions in PM2.5 requires further empirical investigation. Traditional statistical approaches used to study the impact of nonattainment designation on air quality present problems involving indeterministic covariates, confoundedness, model misspecification, and undetected effects at the aggregate level. Our study successfully uses the Panel Data Approach for Program Evaluation (PAMPE) to compare the differences between the actual outcomes and counterfactual outcomes to reveal the treatment effects associated with nonattainment assignment without the burden associated with previous studies. Our results show that, at the monitor level, the air quality improvements obtained by the more-polluted areas were greater after LA County was designated as a nonattainment area. On average, the counterfactual reduction rates derived in our study range from − 0.01 to − 0.15%. Cases in which PM2.5 levels increased occurred at two monitors that were fully or partially compliant during the study period, suggesting the regulatory oversight is indeed spatially heterogeneous.
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Vol.:(0123456789)
Environment, Development and Sustainability (2021) 23:7063–7088
https://doi.org/10.1007/s10668-020-00904-w
1 3
The abatement ofparticulate matter 2.5 inLos Angeles
County: acounterfactual evaluation
Meng‑jieuChen1
Received: 1 April 2020 / Accepted: 22 July 2020 / Published online: 4 August 2020
© Springer Nature B.V. 2020
Abstract
The ambient PM2.5 concentration in Los Angeles (LA) County has been on a decreasing
trend since LA County was designated as a nonattainment area in 2005. However, whether
the nonattainment assignment is the underlying cause of the county’s reductions in PM2.5
requires further empirical investigation. Traditional statistical approaches used to study
the impact of nonattainment designation on air quality present problems involving indeter-
ministic covariates, confoundedness, model misspecification, and undetected effects at the
aggregate level. Our study successfully uses the Panel Data Approach for Program Evalua-
tion (PAMPE) to compare the differences between the actual outcomes and counterfactual
outcomes to reveal the treatment effects associated with nonattainment assignment without
the burden associated with previous studies. Our results show that, at the monitor level,
the air quality improvements obtained by the more-polluted areas were greater after LA
County was designated as a nonattainment area. On average, the counterfactual reduction
rates derived in our study range from −0.01 to − 0.15%. Cases in which PM2.5 levels
increased occurred at two monitors that were fully or partially compliant during the study
period, suggesting the regulatory oversight is indeed spatially heterogeneous.
Keywords Counterfactual baseline· Treatment effect· Panel data approach for program
evaluation· PM2.5· Nonattainment status· Los Angeles County
1 Introduction
The US Clean Air Act requires Environmental Protection Agency (EPA) to establish
National Ambient Air Quality Standards (NAAQS) for criteria pollutants to protect public
health. In the 1970s, national standards were set for ozone, lead, carbon monoxide, sulfur
oxides, and nitrogen oxides. In 1987, EPA also establishes a standard for particulate matter
with a diameter of 10 micrometers or less (PM10). It was not until 1997 that EPA began to
regulate PM2.5, fine particles with a diameter of 2.5μm or less that pose a greater health
* Meng-jieu Chen
mjchen@my.uri.edu
1 Institute fortheStudy ofInternational Aspects ofCompetition, University ofRhode Island,
Kingston, RI02881, USA
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
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