Diesel Exhaust and Asthma

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Diesel Exhaust and Asthma

• Gina M. Solomon, M.D., M.P.H.
• Natural Resources Defense Council
• U.C.S.F. Pediatric Environmental Health Specialty
  Unit

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Asthma Rising

• 42 increase in the U.S. during the last decade
  doubled since 1980
• Among children, 58 increase between 1982 and
  1992
• 1 chronic illness causing school absences
• Deaths increased by 78 from 1980 to 1993.

Changes are too rapid to be genetic
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Children are most susceptible

• Developing body and lungs
• Narrower airways
• Faster metabolism
• Double the breathing rate of adults
• More active

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Patterns of Asthma

• Children gt Adult
• African American gt Latino gt Caucasian
• Urban gt Suburban or Rural
• Busy streets gt Quiet streets

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The Problem of Trucks

• 39,000 children in Italy living on streets with
  heavy truck traffic 60 to 90 increase in
  wheeze, phlegm, and bronchitis
• 3,700 adolescents in Germany living on streets
  with constant truck traffic 71 increase in
  allergic rhinitis, 100 increase in wheezing.

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The number of miles traveled by commercial trucks
in the United States has increased by 235
between 1950 and 1985.
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Diesel and Asthma

• Irritant Effect
• Immunologic Effect
• Adjuvant Effect
• Diesel exhaust may cause asthma

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Diesel as an Airway Irritant

• Triggers oxidative/ inflammatory cascade
• RADS or Irritant-Induced Asthma
• Diesel contains 40 Toxic Air Contaminants,
  many are irritants
• Examples acid aerosols, nitrogen oxides, sulfur
  oxides, volatile organics, metals, oxidants
• Railroad workers riding behind locomotive at
  increased risk of asthma.

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Nitrogen Oxides and Asthma

• Human volunteers exposed to NO2 in the laboratory
  develop airway inflammation
• Daily chronic levels of NO2 linked to asthma
  exacerbations
• Children with asthma more likely to cough,
  wheeze, and have decreased pulmonary function
  when levels of NO2 are high.
• Children living where NOx levels are consistently
  high, are 8-fold more likely to be diagnosed
  with asthma

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Ozone and Asthma

• Causes oxidative damage in the airways
• Aggravates preexisting respiratory disease
• Short-term elevations in ozone linked to hospital
  admissions for respiratory symptoms in children
  under 2
• Increased school absences from respiratory
  disease has been associated with ozone
  concentrations in Nevada and Southern California
• Causes irreversible changes in lung structure,
  which may lead to chronic respiratory illnesses
• Recent research shows a link between long-term
  ozone concentrations in air and new-onset asthma.

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Diesel and Immune Changes

• Diesel exhaust exposure promotes
• IgE release
• Interleukin (IL) release
• Eosinophil production
• Increases in TH2 cells

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The Balance of T-Cells

• TH2 is normally dominant in the fetus
• TH1 begins to dominate after birth with exposure
  to childhood infections and vaccinations
• If TH2 phenotype lingers into childhood,
  allergies are more likely to develop.

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Adjuvant Effect of Diesel Particles

• Egg protein (ovalbumin) (mice guinea pigs)
• Histamine (guinea pigs)
• Japanese cedar pollen (mice)
• Dust mites (mice)
• Ragweed (humans)

Common Ragweed
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How to Create an Allergy

• Expose volunteers to diesel exhaust (1-3 days of
  LA air)
• Expose them to a new protein (KLH)
• Repeat x 3
• Test for immune response.
• KLH IgE TH2 response

Keyhole Limpet
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Diesel Exhaust is likely to .

• Trigger asthma attacks in susceptible asthmatics
• Interact with allergens to increase intensity of
  allergic response
• Cause or contribute to new-onset asthma.