Mobile Source Air Toxics MSATs Assessing ProjectLevel Impacts

Mobile Source Air Toxics (MSATs): Assessing Project-Level Impacts Song Bai, Ph. D. Douglas Eisinger, Ph. D. Deb Niemeier, Ph. D. UC Davis-Caltrans Air Quality Project Presented at the 2007 CAPCOA Health Conference: Understanding and Addressing Health Impacts of Air Pollution on Communities Carson, California September 19, 2007 UC Davis-Caltrans Air Quality Project

Acknowledgments The study team received valuable assistance from: • • Mike Brady, Caltrans Michael Claggett, FHWA David Ipps, Caltrans Jeff Long, California Air Resources Board Jean Mazur, FHWA Dilip Patel, California Air Resources Board Dennis Wade, California Air Resources Board Peng Wu, University of California, Davis UC Davis-Caltrans Air Quality Project

Motivation Mobile Source Air Toxics (MSAT) • February 2006, FHWA interim MSAT guidance • EPA’s original six priority MSATs: – – – Diesel PM Benzene 1, 3 -butadiene Acetaldehyde Formaldehyde Acrolein • Lack of project-level MSAT analysis protocol for California UC Davis-Caltrans Air Quality Project

Outline • Analysis methods and new spreadsheet tool • Example freeway widening project • Results for benzene and diesel PM – Build vs. no-build – surprising findings – Main reasons results occurred – EMFAC 2002 vs. EMFAC 2007 • Conclusions and future research UC Davis-Caltrans Air Quality Project

Analysis Methods Overview: MSAT emissions = emission factors × traffic activity • Obtain TOG and PM emission factors from EMFAC • Obtain MSAT speciation factors from California ARB • Obtain traffic activity data from Caltrans UC Davis-Caltrans Air Quality Project

MSAT Spreadsheet Tool Obtain EMFAC emission factors Calculate composite emission factors Apply MSAT speciation factors Calculate emissions based on activity UC Davis-Caltrans Air Quality Project

Southern CA freeway example Existing: 3 Mixed Flow (MF) lanes each direction Proposed: • 4 MF + 1 HOV • 4 MF + 2 HOV • 5 MF + 1 HOV UC Davis-Caltrans Air Quality Project

Analysis Explored Freeway With Substantial Daily Traffic Activity (Volume) 2004 Base Case (3 MF) 2030 184, 000 increase n/a No-Build (3 MF) 225, 000 22% 4 MF + 1 HOV 291, 000 58% 4 MF + 2 HOV 302, 000 64% 5 MF + 1 HOV 313, 000 70% UC Davis-Caltrans Air Quality Project

2004 vs. Future: Overall Reductions (No-Build) • By 2013: Benzene drops 44% • By 2030: Benzene drops 83% EMFAC 2002 Results UC Davis-Caltrans Air Quality Project

2004 vs. Future: Overall Reductions (No-Build) • By 2013: DPM drops 5% • By 2030: DPM drops 30% EMFAC 2002 Results UC Davis-Caltrans Air Quality Project

Benzene and DPM Results: EMFAC 2002 2030 No-Build (3 MF) vs. Build (4 MF + 2 HOV) • Benzene increases 7% • DPM decreases 6% UC Davis-Caltrans Air Quality Project

Why Are Benzene Emissions Higher in Build Case? • Benzene from non-diesel increases – Limited EF improvement due to speed – Large VMT increase (35%) – High HOV lane speed (emission factor increases) Increased VMT Speed improvement (using g/mile factors) UC Davis-Caltrans Air Quality Project Reduced travel time (using g/minute factors) (sum of exhaust and evaporative benzene)

Why Are DPM Emissions Lower in Build Case? • Speed improvements overwhelm VMT increase – VMT increases only 15% (not as much as non-diesel) – Speed improvement lowers emission factors 15 -25% UC Davis-Caltrans Air Quality Project

Benzene and DPM Results: EMFAC 2002 (Results Shown Previously – Focus on DPM) • Benzene increases 7% • DPM decreases 6% UC Davis-Caltrans Air Quality Project

Same slide as last one, except for EMFAC 2007 • Benzene increases 9% • DPM increases 17% UC Davis-Caltrans Air Quality Project Big Shift from EMFAC 2002

EMFAC 2002 vs. EMFAC 2007 Differences Affecting Diesel PM Speed Corrections EMFAC 2007 - 50 vs. 35 mph: 9% > g/mi emissions EMFAC 2002 - 50 vs. 35 mph: 23% < g/mi emissions UC Davis-Caltrans Air Quality Project

Speed correction: which is closer to reality? EMFAC 2002 UCD Diesel PM SCFs SCF curves: UCD model seems closer to EMFAC 2002 than EMFAC 2007 Key question: at high speeds, are DPM emissions going up or down? UC Davis-Caltrans Air Quality Project

Conclusions and Future Research • • MSAT emissions drop over time Project outcomes can vary by MSAT Results hinge on traffic volumes and speeds Example results – vary by project and model ! Next steps… • Investigate MSAT speciation factors • Test sensitivity to speeds and volumes • Continue to compare EMFAC 2002 vs. EMFAC 2007 UC Davis-Caltrans Air Quality Project

Questions or Comments? UC Davis-Caltrans Air Quality Project

EMFAC 2002 vs. EMFAC 2007 Another Look at Differences Affecting Diesel PM • Diesel VMT proportion changes (40. 6% in EMFAC 2002; 29. 4% in EMFAC 2007) UC Davis-Caltrans Air Quality Project