ORIGINAL CONTRIBUTIONImpact of Changes in Transportationand Commuting Behaviors During the1996 Summer Olympic Games in Atlantaon Air Quality and Childhood AsthmaMichael S. Friedman, MDKenneth E. Powell, MD, MPHLori Hutwagner, MSLeRoy M. Graham, MDW. Gerald Teague, MDDESPITE ADVANCES IN ASTHMAtherapy, asthma remains asubstantial public healthproblem. In the UnitedStates, asthma is a leading cause ofchildhood morbidity, with an esti-mated prevalence of 6.9% in childrenand youth younger than 18 years.1Nu-merous studies have documented a risein the morbidity, mortality, and preva-lence of asthma in different popula-tions.2-8The cause or causes of this trendremain controversial.9-11Experimental, laboratory, and epi-demiologic studies in the last severalyears have linked high concentrationsof known air pollutants to respiratoryhealth problems, most notably exacer-bations of asthma.12-23However, op-portunities to study the health effectsof anthropogenic improvements in airquality are rare. One study found a de-crease in particulate pollution and res-piratory hospital admissions associ-ated with the closure of an industrialfactory in that community.24To ourknowledge, no study has examined theimpact of improved ozone pollution foran extended period of time on asthmaexacerbations or other markers ofasthma morbidity. Also, the extent towhich moderate concentrations ofozone (ie, daily peak of 50-100 ppb)during various exposure lengths af-fects asthma morbidity remains con-troversial.12-16Author Affiliations are listed at the end of this article.Corresponding Author and Reprints: Michael S. Fried-man, MD, Air Pollution and Respiratory Health Branch,National Center for Environmental Health, Centers forDisease Control and Prevention, Atlanta, GA 30333(e-mail: [email protected]).Context Vehicle exhaust is a major source of ozone and other air pollutants. Al-though high ground-level ozone pollution is associated with transient increases in asthmamorbidity, the impact of citywide transportation changes on air quality and childhoodasthma has not been studied. The alternative transportation strategy implemented dur-ing the 1996 Summer Olympic Games in Atlanta, Ga, provided such an opportunity.Objective To describe traffic changes in Atlanta, Ga, during the 1996 Summer Olym-pic Games and concomitant changes in air quality and childhood asthma events.Design Ecological study comparing the 17 days of the Olympic Games (July 19–August 4, 1996) to a baseline period consisting of the 4 weeks before and 4 weeksafter the Olympic Games.Setting and Subjects Children aged 1 to 16 years who resided in the 5 central coun-ties of metropolitan Atlanta and whose data were captured in 1 of 4 databases.Main Outcome Measures Citywide acute care visits and hospitalizations for asthma(asthma events) and nonasthma events, concentrations of major air pollutants, me-teorological variables, and traffic counts.Results During the Olympic Games, the number of asthma acute care events de-creased 41.6% (4.23 vs 2.47 daily events) in the Georgia Medicaid claims file, 44.1%(1.36 vs 0.76 daily events) in a health maintenance organization database, 11.1% (4.77vs 4.24 daily events) in 2 pediatric emergency departments, and 19.1% (2.04 vs 1.65daily hospitalizations) in the Georgia Hospital Discharge Database. The number of non-asthma acute care events in the 4 databases changed –3.1%, +1.3%, −2.1%, and+1.0%, respectively. In multivariate regression analysis, only the reduction in asthmaevents recorded in the Medicaid database was significant (relative risk, 0.48; 95% con-fidence interval, 0.44-0.86). Peak daily ozone concentrations decreased 27.9%, from81.3 ppb during the baseline period to 58.6 ppb during the Olympic Games (P,.001).Peak weekday morning traffic counts dropped 22.5% (P,.001). Traffic counts weresignificantly correlated with that day’s peak ozone concentration (average r=0.36 forall 4 roads examined). Meteorological conditions during the Olympic Games did notdiffer substantially from the baseline period.Conclusions Efforts to reduce downtown traffic congestion in Atlanta during theOlympic Games resulted in decreased traffic density, especially during the critical morn-ing period. This was associated with a prolonged reduction in ozone pollution and sig-nificantly lower rates of childhood asthma events. These data provide support for ef-forts to reduce air pollution and improve health via reductions in motor vehicle traffic.JAMA. 2001;285:897-905 www.jama.com©2001 American Medical Association. All rights reserved. (Reprinted) JAMA, February 21, 2001—Vol 285, No. 7 897The main sources of ambient air pol-lutants are vehicle exhaust, industry,power generation plants, and back-ground contamination. Compared withemissions from nonvehicle sources, therelative amounts of nitrogen oxides, car-bon monoxide, and small particulatematter emitted from vehicles have in-creased disproportionately due to thedramatic increase in worldwide automo-bile use in the past 30 years.12,15Manystudies have found positive associa-tions between traffic density on street ofresidence and either asthma events orasthma prevalence.25-29However, the im-pact of citywide automobile use and traf-fic flow on ambient air pollution andasthma morbidity has not been studied.The 1996 Summer Olympic Gamesin Atlanta, Ga, provided a unique op-portunity to study the relationship be-tween automobile traffic, air quality,and asthma morbidity. Preparations forthe Olympic Games required a strat-egy for minimizing road traffic conges-tion and ensuring that spectators couldreach Olympic events in a reasonableamount of time. Additionally, the morethan 1 million visitors to Atlanta (re-sulting in increased regional transpor-tation demands) could have magni-fied the region’s existing air qualityviolations for ozone pollution that oc-cur each summer. Atlanta’s strategy wassimilar to that used in Los Angeles,Calif, for the 1984 Summer OlympicGames.30It included the developmentand use of an integrated 24-hour-a-day public transportation system, theaddition of 1000 buses for park-and-ride services, local business use of al-ternative work hours and telecommut-ing, closure of the downtown sector toprivate automobile travel, altered down-town delivery schedules, and publicwarnings of potential traffic and airquality problems.31-33METHODSStudy DesignWe used an ecological study design andcompared the 17 days of the 1996 Sum-mer Olympic Games (July 19–August4) to a