Lowering the Ozone Standard: Questionable Costs & Benefits. Michael Honeycutt, Ph.D. Toxicology Division Texas Commission on Environmental Quality

Transcription

1 Lowering the Ozone Standard: Questionable Costs & Benefits Michael Honeycutt, Ph.D. Toxicology Division Texas Commission on Environmental Quality 1

2 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

3 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

4 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

5 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

6 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

7 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

8 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

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10 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

11 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

12 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

13 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

14 Asthma & Hospital Admissions at Ambient Ozone Concentrations Ozone RIA No Significant Change in Morbidity

15 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

16 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

17 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.

18 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

19 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 Change in Mean FEV 1 (%) Change in Mean FEV 1 (%) Ozone Dose (ppm x L) Ozone Concentration (ppm) 19

20 O 3 Dose Response Curves Longer Exposure (6 8 hours) Shorter Exposure ( 3 hours) 20

21 D R Curves with Sensitive Populations Asthmatics have similar lung function responses as health individuals to ozone exposure 21

22 D R Curves with Sensitive Populations Asthmatics and children have similar lung function responses as health individuals to ozone exposure 22

23 Ozone Dose Thresholds 23

24 O 3 FEV 1 Dose Thresholds Mean % Change in FEV 1 Short exposure dose (ppm L) Long exposure dose (ppm L) N/A 24

25 Exercise Ventilation Rates Source Population Exercise Ventilation (L/min) Ventilation (m 3 /day) EPA O 3 ISA 2013 Children (6 11) Sedentary Light Intensity 11 Moderate Intensity 22 High Intensity 42 Young adult (21 31) Sedentary 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) General Population Non Occupational (24 hour day) 14 20

26 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) EPA Sedentary Child EPA Sedentary Adult EPA Light Int Child EPA Light Int Adult TCEQ General Pop (24 hr) Samet Child Outdoor Play EPA Med Int Child TCEQ Adult Worker (8 hr) Zuurbier Adult Bicycle Commute EPA Med Int Adult Samet Child Bicycling EPA High Int Child EPA High Int Adult Samet Adult Male Bicycling

27 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

28 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

29 Thanks! 29

30 2014* County Ozone Design Values Region County Hr 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.

31 Sources of NO x Emissions in Dallas and Houston Areas Source: TCEQ Air Quality Division 31

32 Comparison of O 3 Mortality 32

33 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