The Global Burden of Disease attributable to Ambient Air Pollution:

estimates from the GBD 2010 project

Aaron J CohenHealth Effects Institute

on behalf of the GBD 2010 Ambient Air Pollution Expert Group and the GBD 2010 Collaboration

The Global Burden of Disease attributable to Ambient Air Pollution: estimates from the

GBD 2010 project

• What is GBD 2010?

• Drivers of global health patterns relevant to the ambient air pollution-attributable burden

• Methods for estimating exposure and risk

• The global and regional burdens attributable to ambient air pollution

• Conclusions and implications

Global Burden of Disease 2010

• A systematic scientific effort to quantify the comparative magnitude of health loss for 187 countries from 1990 to 2010. Last major update was for 2000 under the auspices of WHO

• Covering 291 diseases and injuries, 1,160 sequelae of these diseases and injuries, and 67 risk factors or clusters of risk factors

• GBD 2010 study initiated in 2007 funded by Bill and Melinda Gates Foundation

• Summary papers published in a dedicated triple issue of the Lancet December 15th, 2012

http://www.thelancet.com/themed/global-burden-of disease

GBD 2010 TeamGBD 2010 Team

488 authors from 303 institutions in 50 countries 488 authors from 303 institutions in 50 countries

Ambient Air Pollution Expert GroupAmbient Air Pollution Expert GroupH Ross Anderson (Co-Chair) SGHMS U LondonMarkus Amann IIASA/ViennaMichelle Bell Yale UniversityMichael Brauer U British ColumbiaBert Brunekreef U UtrechtRichard Burnett Health CanadaAaron Cohen (Co-Chair) Health Effects InstituteFrank Dentener EC-JRCMajid Ezzati Harvard UniversityBryan Hubbell USEPAKan Haidong Fudan UniversityMichal Krzyzanowski WHO/Euro-Bonn Francine Laden Harvard UniversityStephanie London NIEHSRandall Martin Dalhousie UniversitySumi Mehta UN Fnd Clean Stoves ProgramBart Ostro California EPAKiran Dev Pandey World BankArden Pope Brigham Young UBeate Ritz UCLAIsabelle Romieu IARC Amir Sapkota U MarylandKirk Smith UC BerkeleyGeorge Thurston New York UniversityRita van Dingenen EC –JRCAaron van Donkelaar Dalhousie University

Four Key Drivers of Rapid Changes in Four Key Drivers of Rapid Changes in Global Health PatternsGlobal Health Patterns

1) Demographic transition – increasing population size, substantial increase in the average age in most regions and falling death rates.

2) Cause of death transition – fraction of deaths or years of life lost shifting from communicable, maternal, neonatal and nutritional to non-communicable diseases and injuries despite the HIV epidemic.

3) Disability transition – steady shift to burden of disease from diseases that cause disability but not substantial mortality.

4) Risk transition – shift from risks related to poverty to behavioral risks.

Dramatic Demographic Shifts: Mean Age of Death Rising Rapidly

Percent of DALYs* from Non-Communicable Diseases in 2010: Over 60% in Nearly All Countries Outside of Sub-

Saharan Africa

Disease Burden = Disability-Adjusted Life Years (DALYs) or healthy years of life lost

GBD 2000: Mortality attributable GBD 2000: Mortality attributable to leading risk factorsto leading risk factors

0 1000 2000 3000 4000 5000 6000 7000 8000

High blood pressure

Tobacco

High cholesterol

Underweight

Unsafe sex

Low fruit and vegetable intake

Overweight and obesity

Physical inactivity

Alcohol

Unsafe water, sanitation, and hygiene

Indoor smoke from solid fuels

Iron deficiency

Urban air pollution

Zinc deficiency

Vitamin A deficiency

Contaminated health care injections

Occupational airborne particulates

Occupational risk factors for injury

Lead exposure

Illicit drugs

Mortality in thousands (Total 55.86 million)

High-mortality developing

Lower-mortality developing

Developed

Ezzati et al. 2002; WHO 2002

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GBD 2010: Improving estimation GBD 2010: Improving estimation of Ambient Air Pollution Burdenof Ambient Air Pollution Burden

• Estimate exposure for populations in rural areas and cities <100,000

• Utilize expanded evidence base on air pollution and specific outcomes to estimate burden

• Develop and apply new methods for estimating exposure-response functions

Comparative Risk Assessment 2010:Methods

• Calculate the proportion of deaths or disease burden holding other independent factors unchanged

• Counterfactual analysis: What if risk exposure was at a different level – e.g., lower PM2.5 or normal blood pressure or BMI?

• 67 risk factors and clusters of risk factors

• 20 age groups, both sexes, 187 countries, and for 1990, 2005, and 2010

Estimating the Global Burden of Estimating the Global Burden of Disease due to Ambient Air Disease due to Ambient Air

PollutionPollution

Exposure to Outdoor Air

Pollution

Baseline Incidence

Country- Specific

Mortality, Disease

Concentration –Response

Relationships

Worldwide Health

Evidence

Global Burden, DALYs, Mortality

Risk factor definition: Ambient air pollution

• Air pollution exposures are mixtures

• Relative contribution of different pollutants a function of location-specific• Economic/development, social,

technological factors• meteorology, topography, geography

(transport)

• Literature (measurements) for small number of selected pollutants

• PM (TSP, PM10, PM2.5), O3, NOx, SO2, CO…

Air pollution metricsAir pollution metricsPM2.5

•Most robust indicator in epidemiologic studies

•Biological plausibility supported by toxicology, dosimetry, studies of acute exposures, controlled exposures

•General indicator of combustion source air pollution

•Also incorporates respirable fraction of crustal PM (“dust”)

•Evidence does not support differential risk based on PM2.5 mixture composition

Air pollution metricsAir pollution metrics

Ozone

•Represents somewhat distinct mixture from PM (photochemical oxidation) with different seasonal, spatial and temporal patterns

•Epidemiologic associations (independent from PM) with premature mortality

•Extensive literature of adverse respiratory impacts in controlled exposures

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PM ground-level measurements (2005)

• Measurements: North America, Europe, Australasia

• Estimates (from PM10): Asia, Latin America

• No info: 7 / 21 GBD region

• Global estimates of PM2.5 at 10km x 10km scale

• Combined estimates from satellites (AOD), chemical transport models and ground-level measurements

• Estimates include contribution of all sources of PM2.5

• 1.4 million grid cells in total • Linked to global gridded population (including urban-rural indicators)• Allows for country-level burden estimation

Estimated 2010 levels of PMEstimated 2010 levels of PM2.5 2.5 in China in China

Estimated population-weighted ambient air Estimated population-weighted ambient air pollution levels - PMpollution levels - PM2.52.5 -increased worldwide and in -increased worldwide and in

China 1990-2010China 1990-2010

50% increase in population-weighted PM2.51990 → 2010:

10% increase in global population-weighted PM2.5

• Global: household emissions contribute ~15% (4 µg/m3) of PM2.5

• China: household emissions contribute ~ 15% of ambient PM2.5– about 7µg/m3

Household solid fuel emissions also contribute to Ambient Air Pollution

Estimated 2005 seasonal (3 month) hourly maximum ozone concentrations

(ppb)

TM5 model

• Evidence on adverse health effects of ambient air pollution comprises thousand of peer-reviewed studies, including over 400 epidemiologic studies in China and other parts of Asia since 1980 (HEI Special Report 18 2010)

• Causes of mortality included in GBD estimates for Ambient Air Pollution Exposure were chosen based on systematic reviews of the evidence for:

• Ischemic Heart Disease and Cerebrovascular Disease (US EPA 2009; American Heart Association 2011; WHO 2006; Burnett et al. 2013 in preparation)

• Chronic Obstructive Pulmonary Disease (Schikowski T et al. 2013 In Press)

• Lung Cancer ( Samet and Cohen 2006; IARC Monographs 92, 105, et al.)

• Acute Lower Respiratory Tract Infection <5 yrs (Mehta S et al. 2011)

• Pre-term Birth and Term Low Birth weight (Sapkota A et al. 2011)

• Asthma (Anderson HR et al. 2009; 2011)

GBD 2010 estimates based on systematic review of GBD 2010 estimates based on systematic review of worldwide evidence on health effects of air worldwide evidence on health effects of air

pollution pollution

Diseases affected by air pollution are the top 5 causes of Diseases affected by air pollution are the top 5 causes of the global burden of disease in 2010 the global burden of disease in 2010

(Lozano R et al. 2012)(Lozano R et al. 2012)

A model for estimating the global A model for estimating the global attributable burden: Integrated exposure-attributable burden: Integrated exposure-

response function (IER)response function (IER)• All cohort studies of PM2.5 and

mortality from chronic disease have been conducted in the US and Western Europe

• New models needed to estimate exposure-response functions at high levels of PM in Asia, other regions

• IERs estimate E-R functions using results of studies of second-hand smoke (SHS) , household air pollution (HAP), and active tobacco smoking (ATS) (Burnett R et al. 2013 Submitted)

• Key model assumptions: • Risk is a function of PM2.5 inhaled

dose regardless of source (Pope et al. 2009; 2011)

• Consistent with risk observed in current cohort studies

• Predict risk for highest PM2.5 concentrations consistent with risks from SHS, HAP, active smoking

From: Pope CA et al. EHP 2011

Exposure-response function estimationExposure-response function estimation

• Compiled study‐level estimates of the RR of mortality associated with any or all of ambient air pollution, second‐hand smoke (SHS), household air pollution (HAP), and active smoking (AS) for the following causes: ischemic heart disease (IHD), stroke, lung cancer, chronic obstructive pulmonary disease (COPD), and acute lower respiratory infection (ALRI) in children

• Convert SHS, HAP, and AS to equivalent PM2.5 ambient 24 hour exposure.

• Observed relationship between PM2.5 and CV RR suggested function must be able increase sharply for low concentrations and plateau at very high cigs/day levels (>25~17,000 µg/m3).

• An exponential decay model with a power of concentration – the Integrated Exposure Response function (IER) – is one function that has these properties.

• Model implicitly assumes that RR in ambient range cannot be greater than that for source with highest PM2.5 concentration

• AS for mortality• HAPs for ALRI

• Evaluated a range of non‐linear functions with up to three parameters for fitting the integrated exposure‐response (IER) relationship and evaluated goodness-of-fit using the Bayesian Information Criterion – IER was the functional form that provided the best overall fit

Ambient Air Pollution Cohort Mortality Studies Used to Ambient Air Pollution Cohort Mortality Studies Used to Estimate Integrated Exposure-Response FunctionsEstimate Integrated Exposure-Response Functions

Integrated Exposure-Response Function for IHDIntegrated Exposure-Response Function for IHD

29 Burnett RT, et al. 2013 Submitted

7 µg/m3

GBD risk functions predict risks from recent Chinese cohort GBD risk functions predict risks from recent Chinese cohort study study

Burnett et al. 2013 Submitted

Quantifying UncertaintyQuantifying Uncertainty

• Multiple sources of uncertainty for both the risk function and estimated attributable burden of disease quantified and expressed as uncertainty intervals• Uncertainty in the estimated risk function parameters • Uncertainty in the estimate of PM2.5 • Uncertainty in the counterfactual concentration • Uncertainty in the estimated baseline mortality rates

• Sensitivity analyses • Uncertainty due to model form explored via sensitivity

analysis comparing different model forms • The influence of wind-blown dust on the burden estimates will

be addressed by an analysis in which the counterfactual is increased in dusty regions

Burden of disease attributable to risk Burden of disease attributable to risk factors in the world in 1990factors in the world in 1990

Burden of disease attributable to risk Burden of disease attributable to risk factors in the world in 2010factors in the world in 2010

3.2 million deaths and 76 million DALYs

Risk Factors for global deaths and Risk Factors for global deaths and DALYs in 2010 DALYs in 2010

Risk factor ranks in 2010 by GBD region

Leading risk factor by country in 2010Leading risk factor by country in 2010

Top 20 Mortality Risk Factors Top 20 Mortality Risk Factors in the US, India, and China in 2010in the US, India, and China in 2010

Ambient PM2.5

caused an estimated 1,234,000

deaths; 14.9% of all deaths

in 2010

USTotal attributable deaths

= 103027

ChinaTotal attributable deaths =

1233891

Deaths Attributable to Ambient Particulate Matter Pollution in 2010

IndiaTotal attributable deaths =

627426

Deaths Attributable to Ambient PMDeaths Attributable to Ambient PM2.5 2.5 by by Cause in the US, India, and China in Cause in the US, India, and China in

20102010

DALYs Attributable to Ambient PMDALYs Attributable to Ambient PM2.5 2.5

by Cause in the US, India, and China by Cause in the US, India, and China in 2010in 2010

DALYs Attributable to Ambient Particulate Matter Pollution in 2010

ChinaTotal attributable DALYs=

25227281

USTotal attributable DALYs= 1820412

IndiaTotal attributable

DALYs= 17759991

Ozone and Mortality from COPD in 2010

152,000 (52K, 267K) COPD deaths in 2010

Some conclusions and implications of the Some conclusions and implications of the GBD 2010 estimates GBD 2010 estimates

• Ambient air pollution now ranks among the top 10 global risk factors for lost years of healthy life

• Attributable deaths and DALYs much larger than previously estimated: 3.2 million deaths and 76 million DALYs in 2010 due in large part to mortality from IHD and stroke

GBD 2010 estimates larger than estimated for 2000 : Urban and rural populations included• Larger risk coefficients

• Increases in PM2.5 levels in some regions , e.g. East and South Asia

• Increased rates of IHD, stroke in developing Asia and elsewhere

Some conclusions and implications of the GBD 2010 Some conclusions and implications of the GBD 2010 estimates estimates

Developing Asia contributes over 2/3 of the air pollution-attributable burden of disease due to regional increases in both pollution levels and rising rates of cardiovascular disease: stroke and ischemic heart disease: 4th and 7th leading risk factor in East and South Asia, respectively

The burden of disease attributable to ambient air pollution in East and South Asia has increased from 1990 to 2010 due in large part to increased PM2.5 levels and increased rates of death from stroke and heart disease

Air pollution is an increasingly important cause of lung cancer in developing Asia contributing to WW 20% of lung cancer in China in 2010

Ambient air pollution contributes to the decreasing but still large burden of childhood ALRI in Asia

Some conclusions and implications of the GBD 2010 Some conclusions and implications of the GBD 2010 estimates estimates

The combined public health impact of air pollution, ambient and household, is substantial, and developing Asia experiences some of the highest levels of exposure and the largest burdens of disease from both risk factors in the world

• Given widespread exposures, interventions can be very (cost) effective

• It will require substantial improvements in air quality to achieve the largest benefits from air pollution reduction in very polluted settings

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Thank You ! Thank You !

Aaron Cohenacohen@healtheffects.org

for more information on the GBD Collaboration

http://www.healthmetricsandevaluation.org/gbd