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The TRANSIT Accountability Study: Assessing impacts of vehicle emission regulations and local congestion policies on birth outcomes associated with traffic air pollution

Principal Investigator: 

Oregon State University

This study will assess the effects of emission-control measures on birth outcomes associated with traffic-related air pollution in Texas. Hystad and colleagues will evaluate air quality changes associated with national motor vehicle emissions regulations, as well as a diverse array of local congestion reduction programs implemented in Texas over the past 25 years.

Funded under

The TRANSIT Accountability Study: Assessing Impacts of Vehicle Emission Regulations and Local Congestion Policies on Birth Outcomes in Texas

Perry Hystad1, Mary Willis1, Elaine Hill2, Andrew Larkin1, John Molitor1, Beate Ritz3, Dennis Perkinson4, David Schrank4

1Oregon State University, Corvallis, OR, USA; 2University of Rochester, NY, USA; 3University of California, Los Angeles, CA, USA; 4Texas Transportation Institute, Bryan, TX, USA

Background: In the United States, billions of dollars were spent implementing regulations to reduce traffic-related air pollution (TRAP) from tailpipe emissions from 1990 through today. In addition to emission regulations, local programs have been implemented to reduce traffic congestion, for example, through electronic tolls and managed lanes. Few health studies have empirically evaluated the direct impact of TRAP reductions from these emission regulations and congestion reduction programs, and no studies have examined infant health, which represents an important population health outcome that is strongly linked to air pollution exposures.  

Methods: We will implement the Traffic Regulations And Neonates Study In Texas (TRANSIT) Accountability Study. We will assess changes in birth outcomes in a diverse population-based cohort of 7.6 million births in Texas from 1996-2016 associated with: 1) long-term cumulative regulatory improvements of motor vehicle emissions (and resulting TRAP change), and 2) local congestion reduction programs that may yield TRAP changes in shorter time periods. We will integrate administrative, proprietary, and satellite data sources to purse these questions. Texas is the ideal study area for our proposed project: Texas has a large urban population with large numbers of mothers exposed to TRAP; there has been over a 50% reduction in measured NO2 between 1996 and 2016; detailed longitudinal road network information (with volumes) is available; and many diverse local traffic congestion measures have been implemented across Texas, providing a powerful natural experiment to examine potential benefits to infant health. We will implement econometric-based causal inference methods (e.g. propensity score matching; difference-in-difference analyses) to address our primary hypotheses surrounding the impacts on birth outcomes from long-term cumulative regulatory improvements and local congestion reduction programs.

Results: This research will provide robust new evidence for the impacts of emission regulations and local congestion programs on birth outcomes, an important health outcome linked to TRAP exposures.

Conclusions: Given the scope and magnitude of emission regulations over the last three decades, and growing use of diverse congestion reduction methods, it is important to directly evaluate the potential health benefits and the populations who may benefit the most (or not at all) from associated TRAP exposure reductions.