Near-Roadway Mobile-Source Air Toxics (MSATs) Exposures Along U.S. 95 in Las Vegas, Nevada

1. Near-Roadway Mobile-Source Air Toxics (MSATs) Exposures Along U.S. 95 in Las Vegas, Nevada Prepared by: Paul T. Roberts, Michael C. McCarthy, and Steve G. Brown Sonoma Technology, Inc. Petaluma, California Draft for EPA Webinar Presentation April 30, 2009 Portions previously presented at: CRC Mobile Source Air Toxics Workshop Phoenix, Arizona December 2, 2008 906034.14-3615

2. Outline of this Talk • Background on US95 Settlement Agreement • Introduction to US95 MSAT Study • Ambient Black Carbon Concentrations • Contribution of US95 to BC Concentrations • BC Filtration Efficiencies • Ambient Gas-phase MSAT Concentrations • Mitigation Lessons & Summary

3. US95 Settlement Agreement • A Court Settlement Agreement was reached between Sierra Club and NDOT/FHWA regarding urban freeway expansion where three schools are adjacent to roadway • Both mitigation and monitoring were required to reduce and assess student exposure. • MSAT monitoring study at schools (this study) • Filtration added to HVAC systems at schools • Bus retrofit program • Bus idling education • FHWA gradient study (with EPA)

4. Introduction to US95 MSAT Study • MSAT Study Objectives: • Characterize outdoor and indoor concentrations at schools (student exposure) • Determine US95 vehicle contributions (before and after new lanes opened) • Determine MSAT removal efficiencies of new filtration systems Focus on priority MSATs: diesel particulate matter, benzene, 1,3-butadiene, acrolein, formaldehyde, and acetaldehyde

5. Monitoring Sites at Schools Western High School Fyfe Elementary School Adcock Elementary School Hancock Elementary School

6. Ambient is 20 meters from sound wall (SW); Air inlet is 76 meters from SW. Legend: Air Inlet  Classroom   Ambient Fyfe Elementary School Monitoring Sites North, upwind, 290-70 degrees South, downwind, 110-250 degrees

7. Typical Time-Series of Black Caron Concentration at Fyfe In Winter • BC, CO, NO, OC, EC profiles are similar. • Wind speed, wind direction, source strength have a major influence on concentrations.

8. 8 6 Ambient BC μg/m3 4 2 0 0-1 m/s 1-2 m/s 2-3 m/s >3 m/s Wind speed BC Concentrations Upwind and Downwind Influence of Wind Speed (1 of 2) When winds blow from south to north, observations show a significant difference across the freeway, suggesting freeway influence of BC could be at least 50% of the observed concentrations at these sites. Notch: median, 95% CI Box: interquartile range Whisker: 1.5*IQR Points: beyond 1.5*IQR A significant difference is present if notches do not overlap

9. 8 8 6 6 Ambient BC μg/m3 Ambient BC μg/m3 4 4 2 2 0 0 0-1 m/s 1-2 m/s 2-3 m/s >3 m/s 0-1 m/s 1-2 m/s 2-3 m/s >3 m/s Wind speed Wind speed BC Concentrations Upwind and Downwind Influence of Wind Speed(2 of 2) Adcock upwind Fyfe downwind Adcock downwind Fyfe upwind Same plot as previous slide but with the opposite wind direction Same plot as previous slide At low wind speeds, concentrations upwind/downwind are similar. Only at higher wind speeds are differences evident.

10. Diurnal BC Concentrations; Fyfe Effective filter efficiency: original system about 61%; improved system about 78%

11. Diurnal BC Concentrations Effective filter efficiency: original system about 74%; improved system about 97% Effective filter efficiency: original system about 61%; improved system about 78%

12. Average Black Carbon Exposure

13. Winter 0900-1100 Distributions Samples on 14 days

14. Winter 0900-1100 Distributions

15. Winter 0900-1100 Distributions

16. Winter 0900-1100 Distributions

17. Winter 0900-1100 Distributions

18. Example BC Time-Series Showing Low BC Concentrations in Fyfe Classroom, except when door left open by the teacher (after HVAC changes)

19. Example BC Time-Series Showing Classroom Being Filled with Rush-hour Pollution by HVAC(Before HVAC Changes)

20. Summary of Filtration Characteristics • Modest BC removal with existing HVAC systems in old and new buildings. • Significant BC removal with modified HVAC filtration systems. • Indoor gas-phase MSAT concentrations are often higher than outdoors, including formaldehyde and acetaldehyde (even in older buildings).

21. Mitigation Lessons Learned • Typical HVAC operation will fill classroom with polluted air early in the morning which can result in higher concentrations indoors in mid-to-late morning. • Leaving classroom doors open to outdoor hall can defeat filtration system. • Diurnal pattern of pollution is an important consideration for exposure and mitigation (for both classroom and outdoors).

22. Summary of Near-Roadway MSAT Characteristics (in an Urban Area) • Fresh pollutants go up and down together. • Morning and overnight concentrations dominate outdoor and indoor exposure. • Freeway contributes significant black carbon at all wind speeds. • Low wind speeds often allow high black carbon concentrations on both sides of roadway (with sound wall).

23. Summary of Near-Roadway MSAT Exposure Characteristics • Diurnal pattern of pollution is an important consideration for exposure and mitigation (for both classroom and outdoors). • Exposures lower for elementary school students (09-15) than for high school students (07-13), (than for residents 20-08). • Gaseous MSAT concentration distribution (09-11, 13-15) similar to National distribution, except for formaldehyde and acetaldehyde.

24. Acknowledgments This work was funded by the Nevada Department of Transportation (NDOT); John Terry was the NDOT Project Manager. Joanne Spaulding & Jane Feldman (Sierra Club), Pat Mohn (NDOT, now NDEP), and Rich Baldauf (EPA) contributed to the design of this study. Joey Landreneau and David Vaughn (STI) performed the monitoring and sampling.