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Impact of SO2 on Asthmatics' Peak Flow Rates

Study investigates if SO2 levels within EPA 'safe' zone impair peak expiratory flow rates of asthmatic school children in New Jersey. Research conducted and analyzed by a team of medical and environmental professionals in rural communities.

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Impact of SO2 on Asthmatics' Peak Flow Rates

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  1. Are peak expiratory flow rates of asthmatics impaired by levels of SO2 in the EPA 'safe' zone? The project was reviewed and approved by the University of Medicine and Dentistry of New Jersey’s Institutional Review Boardfor human subject research atRobert Wood Johnson Medical School &New Jersey Medical School. 2005 April 13

  2. April 13, 2005Presented to theNJ CLEAN AIR COUNCILApril 13, 2005 PUBLIC HEARINGon"Air Pollution - Effects on Public Health, Health Care Costs andHealth Insurance Costs"by Stanley H. Weiss, MD 2005 April 13

  3. The full study report is currently draft and is undergoing review by the New Jersey Department of Environmental Protection(DEP) Division of Science Research & Technology (DSR) Bureau of Environmental Health Science and Environmental Assessment. A final report will be provided to the DEP following receipt and responses to any comments. • The report has already been reviewed by DSM. 2005 April 13

  4. AUTHORS • Stanley H. Weiss, MD 1,2,3 • Azadeh Tasslimi, BA1 • Amy Davidow, PhD 1 • Kathy Belby, RN 1 • Shahnaz Alimokhtari, MS 4 • Clifford P. Weisel, PhD 2,3,4 • Department of Preventive Medicine and Community Health, • UMDNJ – New Jersey Medical School, 30 Bergen St, Suite ADMC 1614, Newark, NJ 07107, 973-972-4623 weiss@umdnj.edu • (2) UMDNJ School of Public Health • (3) Co-Principal Investigators • (4) Environmental and Occupational Health Sciences Institute, • UMDNJ – EOHSI/RWJMS, 170 Frelinghuysen Rd, EOHSI 3-314, Piscataway, NJ 08855. 2005 April 13

  5. PURPOSE Determine if changes in peak flow expiratory flow rate (PEFR) among asthmatic school children were related to air pollution from sulfur dioxide (SO2). 2005 April 13

  6. SETTING 3 Rural communities in Warren County, NJ (Northwestern NJ) 1. Belvidere 2. White Township • Harmony Township 2005 April 13

  7. WARREN COUNTY, NJ 2005 April 13

  8. School SurveysFall 2002 A survey of asthma symptoms was conducted of all students with the cooperation of the public schools in the community. In conjunction with review with the school nurses and related f/u, these data were used to determine the actual pediatric and adolescent asthma rates by age, gender and other parameters. Hierarchical estimates of prevalence for the 1641 students (K-12) were: • “Physician-diagnosed, Current Asthma” 11% • “Undiagnosed Current Respiratory Symptoms, that can be consistent with asthma”11%-18% • “Physician-diagnosed Asthma, no current symptoms” 7%-11% • “No Evidence of Asthma” 57%-71% 2005 April 13

  9. PROSPECTIVE STUDY FEBRUARY – JUNE 2003 ELIGIBILITY for ENROLLMENT: All ‘Physician-Diagnosed’ Asthmatic students enrolled in the public school systems of Belvidere, White Township and Harmony Townships and in grades 5 through 12, who had asthma symptoms during the prior year or had prescription medicine for asthma 2005 April 13

  10. WEB-BASED QUESTIONNAIRE • GOAL: Capture All Relevant Information & Minimize # Of Questions Asked In Order To Maximize Participation & Compliance Rate • COMPONENTS (SYMPTOMS AND POTENTIAL MODIFIERS): • General Health, • Prevalence & Severity Symptoms Related to Asthma & Resp Problems, • Measurement of Peak Expiratory Flow Rate • Medication Use, • Encounters w/ Potential Triggers of Asthma (i.e. smoke, animal fur, etc) • DESIGNED WITH PULL-DOWN MENUS SO THAT IT COULD BE • COMPLETED ON A DAILY BASIS AND TAKE LESS THAN 10 • MINUTES 2005 April 13

  11. AIR-MONITORING SITES AIR POLLUTION LEVELS were collected continuously at 3 MONITORING STATIONS: SULFUR DIOXIDE (SO2) Emitted by Coal-powered plants in the area Known respiratory irritant PARTICULATE MATTER BELOW 2.5 microns (PM2.5) Emitted by combustion processes & formed in atmosphere Suggested to be linked to cardiovascular & respiratory ailments OTHER AIR POLLUTANTS (Volatile Organic Compounds - VOCs) Data collected periodically on 70 VOCs, but limited number of measurements 2005 April 13

  12. PROSPECTIVE STUDY • STUDY PARTICIPANTS: • 51% (64/125) of asthmatic students (physician-diagnosed), grades 5-12, were eligible and then gave informed consent to participate • *Higher participation rate in the elementary and middle school than in the high school. • RECRUITMENT INTO STUDY ON ROLLING BASIS: • Start - January 30, 2003 • Last student accepted into the study - May 6, 2003 • All students were asked to continue to enter data until June 19, 2003. Thus, the potential number of days of data entry varied from 45 to 141 days. 2005 April 13

  13. DATA COLLECTED TOTAL # OF STUDENT-DAYS ON WHICH SYMPTOMS, MEDICATIONS, AND PEFR ENTERED = 4,777 TOTAL # OF STUDENT-DAYS ON WHICH W/ SYMPTOMS & MEDICATIONS, BUT NO PEFR ENTERED = 824 TOTAL NUMBER OF STUDENT-DAYS ON WHICH SYMPTOMS & MEDICATIONS WERE ENTERED BY PARTICIPANTS = 5,601 2005 April 13

  14. Data Exclusions • 3 subjects were dropped from analysis who had completed the web-based survey on less than 14 days. • Data Monitoring during the course of the study suggested that 1 subject had unreliable data; he was contacted during the course of the study and he could not resolve critical inconsistencies. • Inconsistencies noted for other students were all satisfactorily resolved. • This left 60 subjects for analysis. 2005 April 13

  15. STATISTICAL ANALYSIS • One monitoring site was at Belvidere HS. Initial statistical analysis was performed using Belvidere residents only, since SO2 was directly measured in their town. • Examined PEFR • Objective measure of respiratory function • Continuous values, which offers analytic advantages • Examined medication use • ongoing/prophylactic/in response to problem • Developed mixed model 2005 April 13

  16. MIXED MODEL • How much the change in peak flow rate is related to other changes (pollution, temperature, and other factors) • Controls for each individual subject • **This is an advantage because PEFR varies with a number of physiological variables, in particular, height, weight, age, & gender (1-6) • Outcome = Natural Logarithm (ln) of PEFR • Method = Mixed Model with a Random • (Subject-level) Effect 2005 April 13

  17. MIXED MODEL • Variables included in Stepwise Assessments: • Daily and daytime (6am-8pm) - maximum and mean: hourly & 5-minute SO2 • mean SO2 (linear & non-linear terms) • same day, 1- and 2-day lagged SO2 • peak and mean same-day, and mean lagged, PM2.5 • Above data are from each of the 3 monitoring stations • mean daytime (7am-6pm) temperature • age, gender • same-day medication use (controller) • pollen (trees, grass, weeds, mold) 2005 April 13

  18. Best Fit for Model • PEAK 5-MINUTE • DAYTIME (6AM-8PM) SO2 from Belvidere • MEAN PRIOR DAY SO2 from Belvidere • DAYTIME TEMPERATURE (7AM-6PM) 2005 April 13

  19. Model applied to White & Harmony using Belvidere HS SO2 Data • Same effect of SO2 seen for White Township students; • Consistent with the Belvidere monitoring station being between a major source of SO2 & White Twp • No statistical association for students in Harmony Township • Harmony in a different direction from the Belvidere monitor • other monitoring site also not appropriate for exposure characterization for Harmony residents • Harmony Twp residents who attend Belvidere HS were included in model 2005 April 13

  20. FULL MODEL RESULTS DESCRIPTION OF STUDY PARTICIPANTS • HARMONY TWP HS STUDENTS - 4 • WHITE TWP STUDENTS - 16 • BELVIDERE STUDENTS - 27 • TOTAL IN FULL MODEL ANALYSIS - 47 • FEMALES - 28 (60%): MALES - 19 (40%) • Age Mean - 13 yrs • Range - 9-19 yrs • Median - 13 yrs 2005 April 13

  21. SO2 values in Belvidere: Ranged up to - • 21 ppb for Daily Mean SO2 • On 16 (11%) of 141 days, the daily mean SO2 was >10ppb • 331 ppb for 5-minute Daytime Peak SO2 • On 14 (10%) of 141 days, the peak 5-minute SO2 was >100 ppb The effect on Peak flow on reaching these 2 levels of SO2 are displayed on the next slide… 2005 April 13

  22. Results of Final PROC Mixed Model With All 47 Subjects 2005 April 13

  23. Analyses were conducted to determine which subjects contributed particularly to the observed associations • The total variability among the peak flow rates was not the same for all students; the study’s statistician examined the contribution of each of the 47 students to the model • The statistical association between SO2 levels and peak flow rates appeared to vary with individuals • 2 students appear highly sensitive to SO2 • 33 students appear to be somewhat sensitive to SO2 • 12 students appear not to be sensitive to SO2 2005 April 13

  24. Post-hoc sub-group Multivariate analyses 2005 April 13

  25. Student A – Bivariate Display of Data Belvidere resident, grade 7, male 2005 April 13

  26. Student B – Bivariate Display of Data White Twp resident, grade 5, male 2005 April 13

  27. Association betweenMean Prior-DaySO2 and PEFR This model predicts overall for the 47 students, that for a 10 parts per billion (ppb) increase in prior-day mean SO2 there is an average decrement in PEFR of 1.1%. For the 2 most sensitive students, this effect was roughly 6 times greater (-5.8%), and this magnitude of effect could be of clinical significance. 2005 April 13

  28. Association between Max Same-DaySO2 & PEFR This model predicts overall for the 47 students, that for a 100 ppb increase in peak same-day SO2 there is an average decrement in PEFR of 0.69% For the 2 most Sensitive Students, this effect was nearly triple (-3.1%). 2005 April 13

  29. CURRENT FEDERAL GUIDELINESSO2 Air Quality Standards • A guideline has been proposed by the US Environmental Protection Agency (EPA), based on the conclusion that in some localized situations, 5-minute SO2 concentrations above 1600 µg/m3 might pose a health threat to sensitive individuals. [Draft Guideline Document for Ambient Monitoring of 5-Minute SO2 Concentrations, EPA, Office of Air Quality Planning and Standards, Research Triangle Park, NC, July 20, 2000; see also http://airqap.com/monitoring/Benchmarks%20for%20SO2%20&%20PM25.htm ]. • This corresponds to an average over the five minutes of 615 ppb. 2005 April 13

  30. CURRENT FEDERAL GUIDELINESSO2 Air Quality Standards • Most air pollution monitors measure the amount of pollution in the air on almost a continuous basis. • Current guidelines assume that higher levels of pollution can be tolerated without effect for short periods of time. • Thus, the National Ambient Air Quality Standards have an averaging time as well as a concentration associated with them. Typically, the longer the averaging time is, the lower is the level of the standard. The averaging times utilized in development of standards represent simplifications of a more complicated statistic. Refer to 40 CFR Part 50 (in the Code of Federal Regulations) for guidance on how the standard are required to be computed for regulatory purposes. 2005 April 13

  31. SUMMARY We observed significant effects on peak flow rate at levels well below the federal 24 hour standard (mean daily value) for SO2 of 140ppb, which had been set to deal with short term effects in the overall population. Some asthmatics appear to be especially sensitive to SO2. Relatively low levels of SO2 had a magnitude of effect on respiratory function that raise clinical concern. Our data suggest that even more transient exposure, to levels far below this guideline, may pose a health threat to sensitive individuals. Further analyses to examine asthma symptoms are in progress. 2005 April 13

  32. LIMITATIONS • The grouping of which students were most sensitive to SO2 was determined through data analysis, not a priori. • Thus, further follow-up may be useful to prospectively assess whether the same students remain sensitive. However, if medication regimens change, this might affect sensitivity. Modeling to incorporate medication changes may be useful, but will be complicated. 2005 April 13

  33. LIMITATIONS • The statistical association does not rule out that the effect is due to an unmeasured factor that correlates with both SO2 and peak flow. • The study was conducted in a single region, and thus cannot be assumed to necessarily generalize to other communities. 2005 April 13

  34. RECOMMENDATIONS • Given that some persons may be especially sensitive to SO2, the definition of what constitutes a “safe level” may need to be revised. • Some asthmatics may need to be especially cognizant of SO2 pollution in their region and may need to attempt to modify their exposure when levels are high. 2005 April 13

  35. Acknowledgements Supported in part by grants from Roche Vitamin (DSM) Inc through the SEP Mechanism of NJ Department of Environmental Protection - see alsohttp://dsmcap.com/ Students & their families who took time to make the entries Special thanks are due to Beecher Zollinger, MD and the school nurses Jill Broscius, RN, Lynn Serniuk, RN, Lois Hampshire, RN, and Donna Golda, RN. 2005 April 13

  36. References • Knudson RJ, Slatin RC, Lebowitz MD, Burrows B. The maximal expiratory flow-volume curve. Normal standards, variability, and effects of age. Am Rev Resp Dis 1976; 113:587-600. • Quackenboss JJ, Lebowitz MD, Krzyzanowski M. The normal range of diurnal changes in peak expiratory flow rates. Am Rev Resp Dis 1991; 143:323-330. • (3) Krzyzanowski M, Quackenboss JJ, Lebowitz MD. Peak expiratory flow rates and symptoms to ambient ozone. Arch Environ Health 1992; 47(2):107-115. • Chiang ST, Han TS. Peak flow rate in relation to age, sex, and anthropometric measurements. Acta Paediatr Scand 1965; 54:439-445. • Hegewald MJ, Capo RO, Jensen RL. Intraindividual peak flow variability. Chest 1995; 107(1):156-161. • (6) Polgar G, Promadhat V. Standard Values: Peak expiratory flow rates and normal values. Pulmonary function testing in children: Techniques and standards. Philadelphia: W.B.Saunders Company, 1971. Pages: 188-194. 2005 April 13

  37. Related Presentations from this Study 1. Tasslimi A, Weisel CP, Belby K, Morales L, Lee N, Weiss SH. Apparent prevalence of adolescent asthma: impacts of asthma definition and sources of information. The 8th Annual Public Health Symposium, held at Rutgers University, Piscataway, NJ, April 7, 2003. 2. Diamond AC, Weisel CP, Lee N, Weiss SH. Design and implementation of an Internet-based questionnaire for daily ascertainment of asthma status in a prospective study. The 8th Annual Public Health Symposium, Rutgers University, Piscataway, NJ, April 7, 2003. 3. Diamond AC, Weisel CP, Lee N, Weiss SH. Design, implementation and monitoring of Internet-based prospective data collection in an epidemiologic study of asthma and the environment. Research Symposium on Genomics, Proteomics, Pharmacogenomics and Bioinformatics. Robert Wood Johnson Medical School, Piscataway, NJ, May 9, 2003. 4. Weiss SH, Tasslimi A, Lee N, Alimokhtari S, Morales L, Hom HL, Weisel CP. Understanding the prevalence of asthma in a community: Impacts of study design and definition. The 131st Annual Meeting (November 15-19, 2003) of the American Public Health Association, San Francisco, Session 4262.0 [Tues, Nov 18, 2003], Abstract #60074. 5. Weisel CP, Weiss SH, Tasslimi A, Diamond A, Alimokhtari S. Use of a web-based questionnaire to collect exposure and symptom data in asthmatic adolescents [abstract]. In: Abstract Book - 14th Annual Conference of the International Society of Exposure Analysis; 2004 Oct 17-21; Philadelphia, PA. Platform W2C Exposure and Health Interface;  Abstract number W2C-03;  p 290. 6. Weiss SH, Tasslimi A, Davidow AL, Weisel CP. Are peak expiratory flow rates of asthmatics impaired by levels of SO2 in the EPA 'safe' zone? The 132nd Annual Meeting (November 2004) of the American Public Health Association, Washington DC, Session 3118.0: Monday, November 8, 2004 (oral). 2005 April 13

  38. Supplemental Slides 2005 April 13

  39. ADVANTAGES IN USING A WEB-BASED QUESTIONNAIRE 2005 April 13

  40. PAPER VERSION Administration of daily questionnaires can be time and labor intensive, paper needs periodic retrieval WEB BASED Web based system accessed by participate at his/her convenience, entry often faster, contact with staff minimized POTENTIAL ADVANTAGES 2005 April 13

  41. PAPER VERSION Compliance, particularly for children/adolescents, is often low for daily questionnaires Compliance rate unknown until attempting to retrieve data WEB BASED Children/adolescents are on computers daily so smaller intrusion in their lives Compliance checked in real time POTENTIAL ADVANTAGES 2005 April 13

  42. PAPER VERSION Paper questionnaires require subsequent entry with associated transcription errors WEB BASED Data is directly added to data base, minimal errors Checks can be made to restrict to valid entries Data can be reviewed quickly so participants can be contacted for questions POTENTIAL ADVANTAGES 2005 April 13

  43. SURVEY INSTRUMENT Section 1 (28 questions) Details on symptoms, triggers, location and peak flow rate Each includes time of day & duration Section 2 Details on medication taken Amount and time of day Picklist and check box entries Entry for current and previous two days permitted Stop & restart after each major section possible 2005 April 13

  44. The home page contains a login, relevant links, important announcements, and information. These are changed periodically. 2005 April 13

  45. SYMPTOM SECTION • Tracking of individual health and asthma related symptoms along with when problems occurred • Exposure to asthma triggers (smoke, allergens, animal, etc) • What microenvironments visited • Peak flow rates (up to 4 values) • Summary verification provided before saving • Internal checks for general and specific symptoms 2005 April 13

  46. 2005 April 13

  47. MEDICAL USE SECTION • Comprehensive medication tracking includes time of intake and dosage • A user’s medications are chosen from a medication database (contains over 200 medications, both prescription and over the counter, characterize by type). • Checks for medicine combinations and dosage that are not medically advisable 2005 April 13

  48. 2005 April 13

  49. CONCLUSIONS • Web Based Questionnaires are feasible for daily entry from adolescent and children (grades 4 – 12) – data from 64 students over 2 – 4 months obtained • Real time monitoring can help improve compliance and quality • When combined with telephone/ e-mail reminders and incentives 2005 April 13

  50. CONCLUSIONS(continued) • Data entry errors are greatly reduced • Entry can be more rapid than paper – (only 5 – 10 minutes per day required) • Has potential for use in large epidemiological studies for population who typically access computer 2005 April 13

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