What is the State of Global Air
The State of Global Air report brings into one place the most
recent information available on levels and trends in air quality
and health for countries around the globe. This year we focus
not only on ambient (outdoor) air pollution but also, for the
frst time, on household air pollution from the burning of solid
fuels for cooking and heating, a major contributor to pollution
both inside and outside the home.
Who is it for
The report is designed to introduce citizens, journalists, policy
makers, and scientists to efforts to estimate and track human
exposure to outdoor and household air pollution and their
impacts on health as part of the comprehensive Global Burden
of Disease project.
How can I explore the data
This report has a companion interactive website, which
provides the tools to explore, compare, and download data
tables and graphics with the latest outdoor and household
air pollution levels and associated burden of disease. These
data are available for individual countries and geographic and
economic regions, as well as for highlighting trends from 1990
to 2016.
Where will I fnd information on:
The Global Burden of Disease and
State of Global Air projects......page 1
Exposure to Ambient Air Pollution:
Levels and Trends ..........page 3
Exposure to Household Air Pollution from Burning
of Solid Fuels: Levels and Trends ..........page 6
Burden of Disease Attributable to Air Pollution page 9
The Key to Air Quality Progress: Understanding
the Major Sources of Air Pollution ......page 16
Numbers, Numbers Everywhere ..........page 19
1STATE OF GLOBAL AIR / 2018
S
tudies from across the world have documented the many
ways in which air pollution can affect people’s health, in-
cluding making it diffcult to breathe for those with asth-
ma or other respiratory diseases, sending the young and
old to hospital or causing them to miss school or work,
and contributing to early death from heart and lung dis-
ease. New studies continue to broaden our understanding of the wide
range of effects that air pollution can have on human health.
This State of Global Air 2018 report presents the latest analysis of
worldwide air pollution exposures and health impacts. It draws from
the most recent evidence (produced in 2016) as part of the Global
Burden of Disease (GBD) project of the Institute for Health Metrics
and Evaluation (IHME) (published in 2017; see Additional Resources
at the end of this report).
As it did last year, the report offers a global update on outdoor, or
ambient
, air pollution. The most recent GBD analysis has continued to
identify ambient air pollution as one of the most important risk factors
contributing to death and disability (see “Defning Ambient Air Pollution”
textbox). Ambient particulate matter (particulate matter less than or
equal to 2.5 micrometers in aerodynamic diameter, or PM2.5), one compo-
nent of air pollution, ranked as the 6th-highest risk factor for early death
(see Figure 1). Worldwide exposure to PM2.5 contributed to 4.1 million
deaths from heart disease and stroke, lung cancer, chronic lung disease,
and respiratory infections in 2016. PM2.5 was responsible for a substan-
tially larger number of attributable deaths than other more well-known
risk factors (such as alcohol use, physical inactivity, or high sodium in-
take) and for an equivalent number of attributable deaths as high cho-
lesterol and high body mass index. Ozone, another important component
of outdoor air pollution, whose levels are on the rise around the world,
contributed to 234,000 deaths from chronic lung disease.
However, the GBD initiative has also documented that millions of
people around the world are exposed to
air pollution in their homes arising from
the use of solid fuels (e.g., coal, wood,
and dung) for cooking and heating. The
GBD 2016 analysis estimates that ex-
posure to “household air pollution” also
has a substantial impact on health and is
ranked 8th in risk factors for early death,
with 2.6 million attributable deaths in
2016. Both individually and collectively,
ambient air pollution and household air
pollution impose a substantial burden on
public health.
To offer a more comprehensive per-
spective on air pollution, this year’s State
of Global Air 2018 provides additional
data on:
Household air pollution — global,
regional, and country-level estimates
of the proportion of populations
exposed to household air pollution
and of the public health burden
attributable to these exposures, and
INTRODUCTION
Fine particle air pollution is the largest environmental
risk factor worldwide, responsible for a substantially
larger number of attributable deaths than other more
well-known behavioral risk factors such as alcohol
use, physical inactivity, or high sodium intake.
Figure 1. Global ranking of risk factors by total number of deaths from all
causes for all ages and both sexes in 2016.
Explore the rankings further at the IHME/GBD Compare site.
2STATE OF GLOBAL AIR / 2018
Defining Ambient Air Pollution
Air pollution is a complex mixture of gases
and particles whose sources and composition
vary spatially and temporally. While hundreds
of different chemical compounds can be mea-
sured in air, governments typically measure
only a small subset of gases and particles
as indicators of the different types of air
pollution and the different types of major
sources contributing to the pollution.
PM2.5
and
tropospheric ozone
(i.e., ozone found in
the atmosphere nearest the earth, where we
live and breathe) are the two indicators used
to quantify exposure to outdoor, or
ambient
,
air pollution in the GBD project.
PM2.5, defned as fne particles with
aerodynamic diameters less than or equal to
2.5 micrometers, is the most consistent and
robust predictor of mortality from cardio-
vascular, respiratory, and other diseases in
studies of long-term exposure to air pollu-
tion.
Long term
is defned by annual average
exposures over several years. PM exposure
is measured in micrograms per cubic meter
(g/m3). Ozone, a harmful gas produced
via the atmospheric reactions of precursor
emissions, has itself been implicated in
increases in mortality from respiratory dis-
ease. When describing exposures to ozone,
scientists focus on seasonal, rather than
annual, average concentrations because
ozone levels are higher in the warm season
in the mid-latitudes where most epidemio-
logical studies have been conducted. Ozone
exposure is measured in parts per billion
(ppb).Exposure to each pollutant is repre-
sented by
population-weighted averages
,
which take into account the proportions of
the population living in areas with different
levels of pollution.
How Are Ambient Air Pollution
Levels Estimated Around the World
Although many high-income countries around
the world operate extensive networks of air
quality monitoring stations in urban areas,
providing continuous hourly measurements
of pollution levels each day, this is not the
case for most countries. These ground-level
measurements of air quality have been
the basis for most studies of the potential
health effects of air pollution and air quality
management. However, other approaches are
needed to provide a consistent view of air
pollution levels throughout the world,
including in the many rapidly developing
urban areas of low- and middle-income
countries and in the large rural and suburban
areas that lack any air quality monitoring
stations. For these areas, scientists rely
on air quality observati