Lowering the Ozone Standard: Questionable Costs & Benefits Michael Honeycutt, Ph.D. Toxicology Division Texas Commission on Environmental Quality 1
Ozone (O 3 ) O 3 is formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react with sunlight NOx is responsible for both formation and scavenging (removal) of O 3 Inhaled O 3 : Is scavenged by antioxidants in the respiratory tract When antioxidants are depleted, it causes a neural reaction that decreases breathing volume, and can cause inflammation, airway hyper reactivity and other responses 2
Health effects attributed to O 3 Severity of Effect Mild Moderate Severe Lung Function Expiratory volume Inflammation Respiratory symptoms Respiratory Morbidity Asthma exacerbation Emergency department visits Hospital admissions Premature Mortality Total (non accidental) Respiratory Cardiovascular All of these effects are putatively occurring at the same concentrations of ozone (in the range of 35 to 72 ppb), with death occurring at lower concentrations than mild effects occur 3
Animal Ozone Concentration Response Relationship Core Principle of Toxicology: The dose makes the poison Hemorrhage Edema Death Shallow breathing Decr. Lung function Inflammation Airway Responsiveness Range of ambient ozone From animal toxicology and human exposure studies, it is implausible that death is occurring at ambient ozone concentrations 4
Moderate & Severe Effects Moderate and severe health effects attributed to O 3 are based largely on ecological epidemiology studies These studies investigate associations between ambient concentrations of O 3 within several days of the health endpoint of interest Pollutant concentrations and potential confounders are calculated at the population level, not at the individual level 5
Ecological Epidemiology Studies Collect death certificates from non accidental deaths Collect ambient O 3 data (1 hr, 8 hr, 24 hr) for time periods preceding death. Repeat going back in time for about 3 days. Correlate changes in O 3 concentration with changes in mortality Produces effect estimates in the form of: % increase in mortality per ppb O 3 increase
8-Hour Ozone Concentrations 5:00 AM 1:00 PM (CST) 36 hrs 3:00 4:00 5:00 6:00 7:00 AM AM AM AM AM 8:00 AM 9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM
2008 DV = 78 ppb From Smith et al 2009 Denver and Colorado Springs are ~70 miles apart. 78 ppb doesn t kill people, but 71 does??? 2008 DV = 71 ppb 2008 DV = 53 ppb
9
EPA: Ozone Attributable Mortality Estimates..the mortality risk metric is generally not responsive to meeting the existing and alternative standard levels Range of U.S. Background Range of Alternative Standards Current NAAQS ACS Study Note: previous investigators did NOT find effect for ozone 10
Change in Ozone Attributable Mortality with Decreasing Ozone Decreasing Mortality Significant Decrease in Mortality No Significant Change in Mortality Significant Increase in Mortality Graph produced from values in Table 7B 2, EPA HREA Appendix 7 Most cities show no change in mortality (and some show increased mortality) with a decrease in the ozone standard Increasing Mortality 11
Change in Ozone Attributable Mortality with Decreasing Ozone Decreasing Mortality Increasing Mortality Significant Decrease in Mortality No Significant Change in Mortality Significant Increase in Mortality Graph produced from values in Table 7B 2, EPA HREA Appendix 7 Most cities show no change in mortality (and some show increased mortality) with a decrease in the ozone standard 12
Asthma Weight of Evidence EPA 21 of 33 studies found no association between ozone and asthma symptoms; those that did were not consistent with one another Pollen confounds results Gradient conducting an asthma WOE 13
Asthma & Hospital Admissions at Ambient Ozone Concentrations Ozone RIA No Significant Change in Morbidity
Mild Effects Mild health effects attributed to O 3 are based largely on human clinical exposure studies Expose human volunteers (usually young and healthy, sometimes children, elderly, and asthmatics) to known concentrations of O 3 Measure lung function changes, symptoms, inflammation, airway hyper responsiveness, epithelial permeability, etc. 15
Clinical Studies These studies measure physiological effects, primarily respiratory function (FEV 1 ) Forced expiratory volume in 1 second (measures how deep a breath you can take) FEV 1 decreases with increasing air toxicant Reversible effect (within minutes to hours) 16
Clinical Data 6.6 hr exposure with heavy exercise 10 20% defined as moderate decrement (US EPA, 2007) Below current NAAQS Adapted from Goodman et al. (2013) Schelegle 72 ppb Exposure 5 of 31 individuals had > 10% decreases and 5 of 31 individuals had increases in FEV 1. Lung function returned to normal within 1 4 hours.
O 3 Dose O 3 dose determined from 3 components: O 3 concentration (in ppm) Time of exposure (in min) Ventilation rate (ie. Exercise level; in L/min) Example Doses: 6.6 hrs (396 min) x 30 L/min x 0.08 ppm = 950 ppm L 2 hrs (120 min) x 40 L/min x 0.2 ppm = 960 ppm L 18
Ozone Dose vs Concentration Dose = Concentration x Ventilation Rate x Duration Dose Response Concentration Response Ozone Dose-Response for 6 hour exposures Ozone Concentration-Response for 6 hour Exposures 4 4 2 2 Change in Mean FEV 1 (%) 0-2 -4-6 -8-10 -12 Change in Mean FEV 1 (%) 0-2 -4-6 -8-10 -12-14 -14-16 0 500 1000 1500 Ozone Dose (ppm x L) -16 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 Ozone Concentration (ppm) 19
O 3 Dose Response Curves Longer Exposure (6 8 hours) Shorter Exposure ( 3 hours) 20
D R Curves with Sensitive Populations Asthmatics have similar lung function responses as health individuals to ozone exposure 21
D R Curves with Sensitive Populations Asthmatics and children have similar lung function responses as health individuals to ozone exposure 22
Ozone Dose Thresholds 23
O 3 FEV 1 Dose Thresholds Mean % Change in FEV 1 Short exposure dose (ppm L) Long exposure dose (ppm L) 0 228.2 668.5 5 606.7 950.7 10 840.4 1618.6 15 1173.1 N/A 24
Exercise Ventilation Rates Source Population Exercise Ventilation (L/min) Ventilation (m 3 /day) EPA O 3 ISA 2013 Children (6 11) Sedentary 4.8 6.9 Light Intensity 11 Moderate Intensity 22 High Intensity 42 Young adult (21 31) Sedentary 5.3 7.6 Light Intensity 12 Moderate Intensity 26 High Intensity 50 Zuurbier 2003 Adult Commuting by bicycle 23.5 Samet 1993 Child Outdoor play 16 Child Bicycling 27 Adult male Bicycling 65 TCEQ Guidance 2012 Adult worker Occupational (8 hour day) 22 10 General Population Non Occupational (24 hour day) 14 20
O 3 Concentration Matrix >4 hour Dose = 1619 ppm L <=4 hour Dose = 840 ppm L FEV 1 Decrement = 10% Ozone Concentration (ppb) Time (hrs) Source Population & Exercise V E (L/min) 1 2 3 4 5 6 7 8 12 24 EPA Sedentary Child 5 2917 1458 972 729 1124 937 803 703 468 234 EPA Sedentary Adult 5 2642 1321 881 660 1018 849 727 636 424 212 EPA Light Int Child 11 1273 636 424 318 491 409 350 307 204 102 EPA Light Int Adult 12 1167 583 389 292 450 375 321 281 187 94 TCEQ General Pop (24 hr) 14 1000 500 333 250 385 321 275 241 161 80 Samet Child Outdoor Play 16 875 438 292 219 337 281 241 211 141 70 EPA Med Int Child 22 636 318 212 159 245 204 175 153 102 51 TCEQ Adult Worker (8 hr) 22 636 318 212 159 245 204 175 153 102 51 Zuurbier Adult Bicycle Commute 24 596 298 199 149 230 191 164 144 96 48 EPA Med Int Adult 26 538 269 179 135 208 173 148 130 86 43 Samet Child Bicycling 27 519 259 173 130 200 167 143 125 83 42 EPA High Int Child 42 333 167 111 83 128 107 92 80 54 27 EPA High Int Adult 50 280 140 93 70 108 90 77 67 45 22 Samet Adult Male Bicycling 65 215 108 72 54 83 69 59 52 35 17 26
Ozone Dose & Exposure Example Threshold of 10% mean FEV 1 decrement (affects sensitive populations) Threshold of 5% mean reversible FEV 1 decrement Threshold with no individual 10% FEV 1 decrements Most ozone doses (based on EPA derived exposure patterns) would change very little with a changing ozone standard, and would be below levels of health concern 27
How is a lower standard good for According to EPA Texas? Houston will have a net increase in mortality No decrease in asthma exacerbations nationwide No decrease in respiratory hospitalizations nationwide Texas will bear 21 38% of the nationwide costs (excluding California) 28
Thanks! 29
2014* County Ozone Design Values Region County 2014 8Hr Ozone DV (ppb) DFW Denton 81 DFW Tarrant 80 HGB Brazoria 80 SAN Bexar 80 DFW Collin 78 DFW Dallas 78 DFW Johnson 76 DFW Hood 76 HGB Montgomery 76 HGB Harris 76 DFW Parker 74 DFW Rockwall 73 ELP El Paso 72 HGB Galveston 72 KTF Bell 72 DFW Ellis 71 NETX Gregg 71 NETX Smith 71 BPA Jefferson 70 DFW Kaufman 70 ARR Travis 69 DFW Hunt 69 NETX Harrison 69 WAC McLennan 69 DFW Navarro 68 BPA Orange 67 CC Nueces 66 BB Brewster 65 VIC Victoria 63 LAR Webb 61 LRGV Cameron 58 MEM Hidalgo 57 *2014 data as of December 2, 2014 and subject to change. Counties in white indicate that the county does not have enough data for a 2014 design value or that there is no monitor located within that county. Only regulatory data shown.
Sources of NO x Emissions in Dallas and Houston Areas Source: TCEQ Air Quality Division 31
Comparison of O 3 Mortality 32
EPA s Ozone HREA, Appendix 7 Significant Decrease in Mortality HREA = Health Risk and Exposure Assessment No Significant Change in Mortality Significant Increase in Mortality 33