1. Revising the AQI for PM2.5: A Challenge for Forecasting and Communication
Nescaum MAC Meeting
April 24-25, 2007
Alison Simcox, EPA New England
(adapted from ppt by John E. White, EPA AIRNow)

2. Overview Changes being considered What some analyses show
What we’ve heard from outside EPA so far…
Next steps for AQI rulemaking

3. Current and Possible PM2.5 AQI

4. The data used for the analysis combined information from both the FRM and continuous PM monitoring networks for the time period between October 2003 and October This period was chosen because most States were reporting their continuous PM data to AIRNOW by the beginning of October Three years were used to take into account varying meteorology over time.
The map shows the average number of days per year that sites across the country measure a 24 hour average greater than 35.5 ug/m3. Only those sites which contained 75% of the data for the three year period were used which would be 845 observations out of a possible The parts of the country that experience a month or more of days per year greater than the 24 hour standard are mostly in the East being heavily concentrated in the Midwest, the Ohio River Valley and the Northeast. The data from the Western United States show that Southern California, the San Joaquin Valley, the Salt Lake Valley and parts of the Northwest would have the largest amount of days greater than 35 ug/m3.

5. Zooming in on the Midwest and Northeast, cities in the Great Lakes and north of the Ohio River valley would see an additional 2 to 3 weeks per year of days greater than the “Moderate” category. Cities along the East Coast would see anywhere from 7 to 10 additional days per year.

6. The following four maps show the distribution for all of the days over the three year period by AQI category for the USA Today cities. What these results show is that for all of the cities, the greatest increase in the number of days between the current AQI and the potential AQI occurs in the “Unhealthy for Sensitive Groups” category. Areas in the Midwest, California and Utah would also mostly see increases in the “Unhealthy” category, but it would not be of the same magnitude as those seen in “Unhealthy for Sensitive Groups”.

7. Additional Analyses…
How many more USG days should we expect each year and each season?
Will episodes (USG+) be longer?
During summer, will more USG days be dominated by ozone or PM2.5?
Will USG days occur with different meteorological conditions?

8. How many more USG days should we expect each year and each season?
Avg. increase in USG days per year
Period: data
Source: AQS
Data types: Continuous and FRM
Locations: Forecast cities in AIRNow (AQS continuous data)
Other cities (AQS FRM data)
Metric: 24-hour averaged values
Some considerations:
75% data completeness
Continuous data useful because available in real-time for forecasting and outreach
Continuous data in AQS may not match the FRM-like data submitted to AIRNow
Examined Forecast cities in AIRNow and core-based statistical areas (CBSA)
Frequency of collection of FRM data varied from daily to every sixth day
Many (70) cities - at least twice as many USG days/yr under proposed standard
Nearly all cities (141) will have at least a 50% increase in number of USG days/ yr
E.g., Boston: 5- 9 days; Atlanta: 9-16 days; Detroit: days; Denver: 2-3 days

9. How many more USG days should we expect each year and each season?
Spring: Mar - May
Fall: Sep – Nov
Summer: Jun – Aug
Winter: Dec – Feb
Peak PM2.5 season may change for many cities; for ex., Chicago: Winter to Summer; Terre Haute: Summer to Fall

10. Will episodes (USG+) be longer?
Detroit
Average number of 3 or more day episodes/yr
Current AQI – July 2005
Proposed AQI – July 2005
Annual Episodes
Multi-day high PM2.5 events more frequent

11. During summer, will more USG days be dominated by ozone or PM2.5?
Dominant pollutant at current and proposed USG threshold, May-September
Chicago, IL
Current
Proposed
USG days 11 15 O3
55%
30% PM
45%
70%
Greenville-Spartanburg, SC
Current
Proposed
USG days 5 10 O3
60%
20% PM
40%
80%
Memphis, TN
Current
Proposed
USG days 12 16 O3
50%
30% PM
70%
Many cities where majority of USG days were dominated by ozone will now have majority of USG days dominated by PM2.5

12. Will USG days occur with different meteorological conditions?
Setting AQI at USG level for lower conc may result in different met conditions conducive for USG conditions
Could impact existing forecast tools
Conceptual models for USG levels
Synoptic and local weather
Transport
Classification and Regression Trees
Synoptic weather analysis: simultaneous observation of weather at many widely located sites using standardized instruments/techniques. By international agreement all met observations taken at same time according to Universal Coordinated Time (UTC) or Z time

13. USG Levels with Different Meteorology
Conducted some case-study & statistical analyses for Eastern cities
More USG days can occur under a transient short-wave ridge
Higher daily average wind speed on additional USG days

14. Likely Effects of Change in AQI
Most cities will have 50% or more increase in USG days/year due to PM2.5
~ 20% of cities will have shift from ozone to PM2.5 -dominated summer season
Some cities will have PM2.5 USG days for 1st time
Many cities will have PM2.5 USG days for added seasons
Some cities will have different peak PM2.5 season
PM2.5 USG days will occur under new met conditions
Want to know the details about your city?
Handouts are available with city-specific statistics

15. Take-home messages
With revised AQI, USG is category that will experience greatest increase in days
Fr most cities, there will be little or no increase in the number of days for AQI categories above “Unhealthy”
Some cities will have USG for the first time or in different seasons
The message to take away from these analyses is that the “Unhealthy for Sensitive Groups” category will see the greatest increase in the number of days if the PM2.5 AQI is revised to reflect the possible changes. There would be little or no increase in the number of days above the “Unhealthy” category for most urban areas.

16. Views from outside EPA so far…
Many like setting AQI at 50 for 15 µg/m3 PM2.5
(WA Dept of Ecology- 13 µg/m3; NESCAUM – 12 µg/m3)
Many like setting AQI at 100 (= standard; like PSI)
Many like setting AQI at 100 for current standard of 35 µg/m3 - no one suggested higher conc
Some said AQI of 100 should be based on health info
Some support setting AQI at 100 for lower conc
(WA Dept of Ecology- 20 µg/m3; NESCAUM - 30 µg/m3)
Some concerned about number of Code Orange days

17. Views from outside EPA so far…
Many like setting AQI at 150 for 55 µg/m3 PM2.5
(WA Dept of Ecology - 35 µg/m3; NESCAUM - 40 µg/m3)
Setting SHL (AQI 500) for 350 µg/m3 PM2.5
WA Depart of Ecology -135 µg/m3
No other comments from outside
EPA will review further
Many think process is taking too long
> 1.5 years since standard revised before revision of AQI
Many revised trigger for air-quality action days last winter
Suggestion that we revise AQI at same time as standards
SHL = significant harm level

18. Next Steps for AQI Rulemaking
Publish proposed rule: late Sept 2007
Followed by official comment period
Publish final rule: Winter 2008
Issue guidance on 1-hr advisories for use during high PM2.5 episodes
Develop outreach & educational materials
Communicate to public that air quality improving

19. Canadian AQHI Color scale different Index Number Category labels
Messages
Forecasts
Did you know...
Who is at risk?

20. Status of Canadian AQHI
AQHI Pilot to be rolled out in June or July 2007
Includes major cities in Canada
National ‘production’ in 2008
Focus-group testing underway
"AQHI" not final (but won't be called AQI)
EPA getting more technical info about AQHI
Will distribute to AQHI/AQI workgroup
Monthly conf calls through summer
Possible AQHI-forecast training for US forecasters
Tele-training possible