The Global Burden of Disease Due to Urban Air Pollution: Estimates and Uncertainties

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The Global Burden of Disease Due to Urban Air
Pollution Estimates and Uncertainties

• Aaron Cohen
• Health Effects Institute

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CRA project and WHR 2002
www.who.int/whrwww.thelancet.com
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Urban Air Pollution Working Group

• H Ross Anderson (Co-Chair) SGHMS U London
• Aaron Cohen (Co-Chair) Health Effects Institute
• Kersten Gutschmidt WHO/Geneva
• Michal Krzyzanowski WHO/Euro-Bonn
• Nino Künzli University of Basel
• Bart Ostro California Health Dept
• Kiran Dev Pandey World Bank
• Arden Pope Brigham Young
• Isabelle Romieu PAHO
• Jonathan Samet Johns Hopkins
• Kirk Smith UC Berkeley

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The Global Burden of Disease Due to Urban Air
Pollution Estimates and Uncertainties

• The Global Burden of Disease Comparative Risk
  Assessment
• Estimating the Global Burden of Disease Due to
  Urban Air Pollution
• Magnitude and distribution of the attributable
  burden
• Major sources of uncertainty
• Estimating the avoidable burden

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Risk factors in CRA
Child maternal under-nutrition Childhood and
maternal underweight Iron deficiency Vitamin A
deficiency Zinc deficiency Other
nutrition-related risks inactivity High blood
pressure High cholesterol Overweight and
obesity Inadequate fruit and vegetable intake
Physical inactivity Addictive substances
Smoking and oral tobacco Alcohol Illicit drugs
Sexual and reproductive health risks Unsafe sex
Non-use and ineffective use of contraception
Environmental risks Unsafe water, sanitation,
and hygiene Urban air pollution Indoor smoke
from solid fuels Lead exposure Climate change
Occupational risks Risk factors for injury
Carcinogens Airborne particulates Ergonomic
stressors Noise Other selected risks to health
Contaminated health care injections Child
sexual abuse Distributions of risks by poverty
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14 WHO mortality sub-regions
A very low child and adult mortality B low
child and adult mortality C low child, high
adult D high child, high adult E high child,
very high adult
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Basic CRA framework and goals

• Risk factor-disease relationships
• risk accumulation
• risk reversal

• Risk factor levels
• current distribution
• counterfactual
• distribution(s)

Disease burden
Attributable burden in 2000 Avoidable burden in
2010 2020
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Mortality and Burden of Disease

• Mortality Numbers of Deaths
• Burden Disability Adjusted Life Year or DALY
• DALY YLL YLD
• years of life lost because of premature death
  (YLLs)
• years of life lived with disability (YLDs)
• one DALY one lost year of healthy life

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Applying the CRA Methods to Urban Air Pollution

• Choice of indicator pollutant and estimation of
  ambient concentrations
• Choice of risk factor-disease relationships
• Calculation of disease burden

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Estimated PM10 Concentration in World Cities (pop
gt100,000)
PM10 (µg/m3) . 5-14 . 15-29 . 30-59 .
60-99 . 100-254
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Population Distribution of Estimated PM10 Levels
for 3200 Cities
Cohen et al 2004
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American Cancer Society II Cohort 500, 000
adults followed 1982 1998 (Pope et al JAMA
2002)
RR per 10µg/m3 PM2.5 1979-83 RR per 10µg/m3 PM2.5 1979-83 RR per 10µg/m3 PM2.5 1979-83
RR 95 CI
Cardiopulmonary 1.06 1.02-1.10
Lung Cancer 1.08 1.01-1.16

Random effects Cox proportional hazards model
controlling for age, sex, race, smoking,
education, marital status, body mass,
alcohol, occupational exposure and diet
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Alternative Scenarios for Burden of Disease
Estimation for Urban Air Pollution
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Percent change in mean daily number of child and
infant deaths
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Estimation of attributable deaths and DALYs

• 1. Calculate region specific relative risk
• RR2.5 exp CR (X 7.5)
• where CR is slope of the C-R function (ß
  coefficient) and X is regional population
  weighted mean PM.
• 2. Calculate Attributable Fraction (AF)
• AF P(RR-1) / P(RR-1)1
• where P is proportion exposed, i.e. proportion
  living in cities
• 3. Calculate attributable deaths and DALYs
• (AF regional totals)

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Estimated Burden of Urban Air Pollution Worldwide
(95 confidence intervals)
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Fraction of Deaths Attributable to Outdoor Urban
Air Pollution by Region
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Mortality attributable to leading risk factors
Ezzati et al. 2002 WHO 2002
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Burden of disease attributable to leading risk
factors
Ezzati et al. 2002 WHO 2002
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Summary results for individual risks

• Substantial disease burden associated with risk
  factors such as under-nutrition, poor water and
  sanitation, and indoor air pollution remain,
  especially in the poorest developing countries
• Simultaneously risks from a number of factors
  such as smoking, alcohol, and obesity are
  becoming increasingly global
• Some risks, like urban air pollution and lack of
  contraception are major causes of burden in
  specific regions

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The Burden of Disease Due to Air Pollution from
Multiple Sources in Asia
HEI 2004
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Excess Deaths from Selected Environmental Factors
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Uncertainties that we quantified

• Random variation in exposure and risk coefficient
  estimates
• Choice of PM2.5/PM10
• Choice of counterfactual level
• Choice of concentration-response function
  coefficients and extrapolation

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Sensitivity of Attributable Mortality Estimates
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Uncertainties that we did not quantify

• Burden due to pollutants other than PM, e.g.,
  ozone
• Burden in cities with populations lt100 K
• Effects of exposure at finer spatial scales e.g.,
  due to proximity to vehicular traffic
• Relative toxicity of PM from different sources
• Contribution of other potentially important
  health outcomes, e.g., LBW, infectious disease

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Sources of fine particulate air pollution Delhi
2001
Winter
Winter
Georgia Tech (USA) 2004
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Differential Toxicity of PM from Biomass and
Fossil Fuels
Mudway et al. Particle and Fibre Toxicology 2005
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Spatial Analysis of Air Pollution and Mortality
in Los Angeles ACS Cohort Jerrett et al. 2005

• Air pollution excess relative risks (per
  10µg/m3) for all-cause, IHD and lung cancer
  mortality 2-3 times as large in small-area
  (within-city) analyses as in inter-urban analyses
  reported by Pope et al. 2002 and used for GBD
  estimates

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Leading Causes of Mortality and Burden of Disease
2002
Mortality
DALYs

• 
  
• Perinatal conditions 6.5
• Lower respiratory infections 6.1
• HIV/AIDS 5.7
• Depression 4.5
• Diarrhoeal diseases 4.2
• Ischaemic heart disease 3.9
• Cerebrovascular disease 3.3
• Malaria 3.1
• Road traffic accidents 2.6
• Tuberculosis 2.3
• COPD 1.9

• 
  
• Ischaemic heart disease 12.6
• Cerebrovascular disease 9.7
• Lower respiratory infections 6.8
• HIV/AIDS 4.9
• COPD 4.8
• Perinatal conditions 4.3
• Diarrhoeal diseases 3.2
• Tuberculosis 2.7
• Lung cancer 2.2
• Malaria 2.2
• Road traffic accidents 2.1

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Pediatrics 2005115121-128
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8.9 Million Cases
1.6 Million Deaths
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Air Pollution and TB
Millions of Deaths ( in developing countries) Global Burden of Disease ( in developing countries) Range of reported TB relative risk estimates
Tuberculosis 1.6 (gt90) 2.5 (gt90)
Smoking 4.8 (50) 4.1 (gt50) 1.5-4.5 (ever/never)
Indoor Air Pollution 1.6 (gt95) 2.6 (gt95) 1.8-3.6 (solid fuel use)
Urban Outdoor Air Pollution 0.8 (gt70) 0.4 (gt70) None reported

Modified from Baris and Ezzati 2004
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Attributable and avoidable burden
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What determines the health effects of air
pollution as economies grow?

• Number of people in cities
• Sources of air pollution
• Emissions
• Air quality
• Susceptibility

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An Increasingly Urban Population(data from UN/UN
Centre for Human Settlements 1995-2002)
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Development and Combustion of Fossil Fuels for
Energy Generation/ Transportation(Data from
International Energy Agency 2002 and M Walsh 2001)
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UK SO2 Emissions and Electricity
Generation1970-1995
Figure from Williams ML 1999
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Number of people at high CV risk 2000 - 2010 (A
Rogers 2005)
36 m
46 m
38 m
18 m
50 m
16 m
45 m
5 m
5 m
12 m
7 m
19 m
1 m
4 m
gt175 million people at 25 risk of a major CV
event in the next decade, by WHO subregion
A very low child and adult mortality B low
child and adult mortality C low child, high
adult D high child, high adult E high child,
very high adult
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Reductions in Mortality in Dublin 72 Months Pre-
vs. Post-1990 Ban on Coal Sales
Clancy et al. Lancet 2002
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Thank You

• acohen_at_healtheffects.org