The Public Health The Public Health Significance of Air Significance of Air

PollutionPollutionSteve ClarksonSteve Clarkson

A Brief HistoryA 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

http://www.epa.gov/airnow//health-prof/EPA_poster-final_lo-res.pdf

Health Effects of Air Pollution :Health Effects of Air Pollution :Key Findings IKey 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

Recent Highlights – Short-term Recent Highlights – Short-term EffectsEffects

• Activity diaries from patients who had suffered heart attacks

• Exposure to traffic in hour prior to heart attack appeared to be trigger

Gage Occupational & Environmental Health Unit

CONTROLLED HUMAN EXPOSURE FACILITY AND PARTICLE CONCENTRATOR

• Statistical problem identified affecting time-series studies (mortality, hospital admissions)

• Numerous studies affected

• Suggested effects could be smaller and less certain than previously thought

• 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

Health Effects of Air Pollution :Health Effects of Air Pollution :Key Findings IIKey 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

Recent Highlights – Long-term Recent Highlights – Long-term EffectsEffects

• 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

• Used data from two clinical trials on atherosclerosis prevention

• Mapped study subjects to PM2.5 exposure

• Exposure was associated with atherosclerosis in carotid artery

• 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

Policy InitiativesPolicy Initiatives

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

Key pointsKey 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

Extra slidesExtra slides

• 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)

Recruitment:• Healthy

subjects (n=35)

• 18-50 yr• No heart &

lung conditions• Nonsmoker

Downtown

Tunney’s Pasture

Ultrasound for vascular reactivity

Serum for ET-1

Heart Rate

Blood pressure

PM2.5, PM1, NO2, weather

Traffic count

Bob Dales, Ling Liu, Mieczyslaw Szyszkowicz, Jeff Willey, Ryan Kulka, Neil Ballack

Health CanadaTerrence Ruddy, Mary Dalipaj

University of Ottawa Heart Institute

MORNING SLATER STREET, OTTAWAMORNING SLATER STREET, OTTAWA

N Engl J Med 2005;352:1276-a

• 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

Do interventions to control air Do interventions to control air pollution have a measurable pollution have a measurable

impact on health?impact on health?

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