NAAQS Altitude Effects

1. NAAQS Altitude Effects Ozone Transport Commission Annual Meeting June 11, 2014 Baltimore, MD Will Ollison 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org

2. Compliance with PM NAAQS PM2.5/10 compliance addresses altitude effects. • 40 CFR Part 50, Appendix L, Section 2.2: Each filter is weighed…before and after sample collection to determine the net gain due to collected PM2.5. The total volume of air sampled is determined by the sampler from the measured flow rate at actual ambient temperature and pressure and the sampling time. The mass concentration of PM2.5 in the ambient air is computed as the total mass of collected particles in the PM2.5 size range divided by the actual volume of air sampled, and is expressed in micrograms per cubic meter of air. • 40 CFR Part 50, Appendix J, Section 2.2: …For PM10 samples collected at temperatures and pressures significantly different from EPA reference [25°C, 1 atm] conditions, these corrected concentrations sometimes differ substantially from actual concentrations,…particularly at high elevations. Although not required, the actual PM10 concentration can be calculated from the corrected concentration, using the average ambient temperature and barometric pressure during the sampling period. 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org

3. Compliance with O3 NAAQS O3 compliance does not address altitude effects. • 40 CFR Part 50 Appendix P, Section 2.2: The standard-related summary statistic is the annual fourth-highest daily maximum 8-hour O3 concentration, expressed in parts per million, averaged over three years. The 3-year average shall be computed using the three most recent, consecutive calendar years of monitoring data meeting the data completeness requirements described in this appendix. The computed 3-year average of the annual fourth-highest daily maximum 8-hour average O3 concentrations shall be reported to three decimal places (the digits to the right of the third decimal place are truncated, consistent with the data handling procedures for the reported data). • O3 photometers calculate and report parts per million mixing ratios from measured actual concentrations at absorption tube temperatures and pressures. These mixing ratio O3 compliance metrics are pressure invariant and do not change with altitude. • At a given O3 ppm level and breathing rate less O3 mass is inhaled at higher altitudes, penalizing highlanders into complying with lower effective NAAQS than lowlanders. 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org

4. OTC State 2010-2012 Design Values - Monitors > 1000 feet 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org

5. OTC State 2010-2012 Design Values - Monitors > 1000 feet 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org

6. Recommendations • Since EPA will use high elevation rural/remote CASTNet O3 monitor design values for 2011-2013 NAAQS compliance determinations, and • Since CASAC will recommend EPA reduce the 75 ppb O3 NAAQS into the 60-70 ppb mixing ratio range, and • Since CASAC-AMMS will recommend a new interference-free O3 Federal Reference Method, • OTC States should (1) request that EPA expedite upgrades of existing OTC network O3 monitors to interference-free status and (2) account for altitude effects in any revised mixing ratio O3 NAAQS. • Request that EPA to account for altitude effects in gaseous NAAQS 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org