NAAQS Altitude Effects Ozone Transport Commission Annual Meeting June 11, 2014 Baltimore, MD Will Ollison 1220 L Street, NW Washington, DC

Compliance with PM NAAQS PM 2.5/10 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 L Street, NW Washington, DC

Compliance with O 3 NAAQS O 3 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 O 3 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 O 3 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). O 3 photometers calculate and report parts per million mixing ratios from measured actual concentrations at absorption tube temperatures and pressures. These mixing ratio O 3 compliance metrics are pressure invariant and do not change with altitude. At a given O 3 ppm level and breathing rate less O 3 mass is inhaled at higher altitudes, penalizing highlanders into complying with lower effective NAAQS than lowlanders L Street, NW Washington, DC

OTC State Design Values - Monitors > 1000 feet State Height (feet) < 75 ppb< 70 ppb< 65 ppb< 60 ppbMonitor Alt Adj < 75 ppb Alt Adj < 70 ppb Alt Adj < 65 ppb Alt Adj < 60 ppb CT1519 YESNO YES NO ME MD MA MA NH NH NH NY NY NY NY NY NY NY VT VA VA VA VA L Street, NW Washington, DC

OTC State Design Values - Monitors > 1000 feet State Height (feet) < 75 ppb< 70 ppb< 65 ppb< 60 ppbMonitor Alt Adj < 75 ppb Alt Adj < 70 ppb Alt Adj < 65 ppb Alt Adj < 60 ppb PA1261NO YESNO PA PA PA PA PA PA PA PA PA PA PA PA PA PA PA PA L Street, NW Washington, DC

Recommendations Since EPA will use high elevation rural/remote CASTNet O 3 monitor design values for NAAQS compliance determinations, and Since CASAC will recommend EPA reduce the 75 ppb O 3 NAAQS into the ppb mixing ratio range, and Since CASAC-AMMS will recommend a new interference-free O 3 Federal Reference Method, OTC States should (1) request that EPA expedite upgrades of existing OTC network O 3 monitors to interference-free status and (2) account for altitude effects in any revised mixing ratio O 3 NAAQS. Request that EPA to account for altitude effects in gaseous NAAQS 1220 L Street, NW Washington, DC