The Public Health Significance of Air Pollution

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The Public Health Significance of Air Pollution
Steve Clarkson
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A Brief History

• 1930s-60s severe air pollution episodes Meuse
  Valley, Belgium, Donora, Pennsylvania, London,
  U.K.
• 1960s-70s introduction of clean air legislation
• 1970s-80s significant reduction in ambient
  concentrations of many pollutants
• 1980s, early 1990s studies demonstrating adverse
  effects even at lower levels of exposure
• Mid to late 1990s large number of studies
  replicated findings worldwide
• Late 1990s-present evaluation of nuances of
  associations observed in epidemiological studies,
  effects of specific sources, biological
  mechanisms, long term effects

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http//www.epa.gov/airnow//health-prof/EPA_poster-
final_lo-res.pdf
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Health Effects of Air Pollution Key Findings I

• Know more about short term effects
• More people die and are admitted to hospital for
  heart and lung problems on days with elevated
  levels of air pollution
• These effects are the tip of the iceberg
  relative to other, milder effects
• A variety of biological mechanisms have been
  identified for these effects
• Effects found at levels previously thought to be
  safe
• Effects observed using widely varying study
  designs large scale population studies to
  controlled laboratory studies in humans/ animals

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Recent Highlights Short-term Effects
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• Activity diaries from patients who had suffered
  heart attacks
• Exposure to traffic in hour prior to heart attack
  appeared to be trigger

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CONTROLLED HUMAN EXPOSURE FACILITY AND PARTICLE
CONCENTRATOR
Gage Occupational Environmental Health Unit
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• Statistical problem identified affecting
  time-series studies (mortality, hospital
  admissions)
• Numerous studies affected
• Suggested effects could be smaller and less
  certain than previously thought

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• Impact of statistical problem varied from study
  to study
• In many cases size of effect smaller and less
  precise
• Significant associations persisted in most studies

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Health Effects of Air Pollution Key Findings II

• Know less about long term effects
• People do not live as long in cities with high
  air pollution
• Air pollution may contribute to
• Adverse pregnancy outcomes
• atherosclerosis
• the development of lung cancer and chronic lung
  disease

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Recent Highlights Long-term Effects
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• Sample of 5,000 subjects from Netherlands Study
  on Diet and Cancer
• Mapped 1986 address to proximity to major roads
• Follow-up 1986-1994
• Those living near major roads twice as likely to
  die from cardiopulmonary causes

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• Used data from two clinical trials on
  atherosclerosis prevention
• Mapped study subjects to PM2.5 exposure
• Exposure was associated with atherosclerosis in
  carotid artery

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• evidence of link with birth outcomes
• Evidence strong enough to suggest causal link
  with low birth weight
• Link with preterm birth, IUGR, congenital
  anomalies is weaker
• Variety of possible biological mechanisms

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Policy Initiatives

• Low sulphur gasoline
• Canada Wide Standards
• Canada-U.S. Air Quality Agreement
• Kyoto Protocol
• Health-risk based Air Quality Index

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Key points

• There is a very large and growing evidence base
  linking air pollution at current levels with
  adverse health effects
• There is more evidence about short term effects,
  but more evidence is now appearing on long term
  effects
• The latest research focuses on effects on the
  cardiovascular system and of specific pollution
  sources like traffic
• A number of policy initiatives have been
  undertaken to reduce the health burden from air
  pollution

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Extra slides
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• From a study of air pollution and mortality in
  Europe
• 30 cities
• Applied variety of models
• Best fit from linear model
• Similar evidence from 20 largest US cities
  (NMMAPS)

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Bob Dales, Ling Liu, Mieczyslaw Szyszkowicz, Jeff
Willey, Ryan Kulka, Neil Ballack Health
Canada Terrence Ruddy, Mary Dalipaj University of
Ottawa Heart Institute
PM2.5, PM1, NO2, weather
Traffic count

• Recruitment
• Healthy subjects (n35)
• 18-50 yr
• No heart lung conditions
• Nonsmoker

Downtown
Ultrasound for vascular reactivity
Heart Rate
Blood pressure
Serum for ET-1
Tunneys Pasture
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MORNING SLATER STREET, OTTAWA
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N Engl J Med 20053521276-a
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• 4000 subjects from prevention and incidence of
  asthma and mite allergy study
• At 2 years of age, some evidence of associations
  of modelled exposures to NO2, PM2.5 and soot
  with respiratory outcomes
• Need for extended follow-up

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Do interventions to control air pollution have a
measurable impact on health?
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• Unusual Opportunity
• Natural experiment
• Dramatic (70) reduction in pollutant
  concentration over short period
• Control communities readily available
• Death rates decreased measurably by 15.5 in
  case of deaths from respiratory causes