Children's Exposures/Health Effects/Diesel Exhaust
Condition: Asthma; Airway Inflammation
MeSH terms: Inflammation
Study type: Observational

Summary: 
      The contribution of diesel exhaust (DE) to health, especially children's health, is of
      tremendous public health interest. DE has been associated with worsening asthma and
      allergies, among other important health effects. Reducing DE exposures has become a major
      regulatory initiative, and federal, state, and local jurisdictions are investing hundreds of
      millions of dollars in retrofitting diesel engines in school buses and other changes to reach
      this goal.

      The U.S. Environmental Protection Agency's recent regulations require all on-road diesel
      vehicles to change to low emission engines and ultra-low-sulfur fuels by 2007 (US EPA '00).
      In spring 2003, the U.S. EPA announced a nationwide voluntary school bus retrofit initiative.
      In July 2003, the Washington Legislature enacted a statewide "Diesel Solutions" program that
      provides 25 million dollars by 2008 to retrofit school diesel buses with cleaner burning
      engines and fuels, making it one of the largest and most active voluntary school bus retrofit
      program in the country. If risk assessment estimates are accurate, these changes will have a
      large public health impact, especially on children who ride school buses daily. However, no
      studies to-date have rigorously examined school children's exposure to diesel exhaust (DE)
      and its health effects, nor such a significant change in vehicular pollution control. We
      propose to seize this opportunity of a large natural experiment taking place in the Puget
      Sound area and conduct a study to assess health effects from diesel bus exhaust before and
      after the retrofit of diesel bus fleets between 2005 and 2007. The specific aims of the study
      are to:

        1. Determine whether asthmatic children changing to retrofitted buses with cleaner fuels
           and engines have a reduction in sub-clinical and clinical asthma severity.

        2. Determine if increased levels of DE exposure lead to an increase in acute clinical and
           sub-clinical features of asthma in children.

        3. Quantify the levels and changes in particle and toxic gas exposures to DE in 3 groups of
           children commuting to school by retrofitted buses or private cars, old diesel buses to
           be retrofitted later, and old diesel buses through the study.

      Sub-aim 3: Use the time-activity information, personal exposure measurements, and on-bus
      monitoring data to construct an exposure model to predict individual exposures to DE for all
      subjects.
    

Detailed description: 
      We will recruit 450 subjects ranging from 9 to 11 years old (or 3rd to 5th graders). These
      children who commute to school will perform repeated monthly measures of pulmonary function
      tests using spirometry, pulmonary inflammation via exhaled breath, and asthma symptoms and
      clinical encounters, up to 3 school years. These 500 children will represent 3 exposure
      scenarios: 1) one group of 125 children riding retrofitted school buses or private cars; 2)
      250 children riding old buses who will change to retrofitted buses during the first or second
      year of the study; and 3) 125 children who ride old diesel buses through the study. All
      subjects will be either healthy or having physician-diagnosed asthma with severity ranging
      from mild intermittent to moderate persistent. Personal exposure monitoring of particulate
      matter, CO, NO2, and SO2 will be performed on a subset of 144 asthmatic subjects, with each
      subject being monitored for up to 2 days, in each monitoring year.

      Subjects participating in the study will wear a small backpack containing several personal
      air monitors measuring real-time particulate matter concentrations and carbon monoxide
      concentrations as well as integrated (24 hour averaged) measurements of SO2 and NO2. The
      children's personal monitoring will begin when they wake up in the morning and continue for
      24-hours. When wearing the backpack is inconvenient, such as when sleeping, the monitoring
      equipment should be placed in close proximity to the subject. Once the subject arrives at
      school, s/he will be asked to perform three respiratory tests: exhaled nitric oxide, exhaled
      breath condensate, and spirometry. At the end of the school day, the subject will be asked to
      perform the same two tests of lung function as earlier, plus an additional test of exhaled
      breath condensate. The subject will then continue his/her day as normal. A technician will
      replace the filter in the particulate matter monitor between 6 and 7 PM. We will repeat the
      same monitoring procedure the following morning when the subject wakes up for another 24-h.
      Monitoring will stop on the third morning when the subjects wake up. In addition to the
      personal monitoring, a monitoring kit will be installed in the subject's school bus and will
      be operated by a technician. This in-vehicle monitoring kit includes everything contained in
      the personal monitoring kit, plus a P-TRAK (TSI, model 8525) for real-time ultra-fine
      particle counts, two Harvard Personal Environmental Monitors (HPEM) with Teflon and quartz
      filters respectively for determining elemental carbon fractions, an EcoChem PAS2000CE monitor
      for polycyclic aromatic hydrocarbons (PAHs), and a global positioning system personal
      acquisition logger (GPS-PAL). The following timeline shows the typical daily schedule for a
      subject participating in the study.
    

Time perspective: Prospective
Keywords: Asthma; Diesel exhaust