Air Pollution and Health

Recent Findings and Next Steps

Antonella Zanobetti

Principal Research Scientist

Department of Environmental Health

Harvard T.H. Chan School of Public Health

Background• Adverse effects of air pollution on health: 3 disasters in

which high levels of air pollution associated with high

number of deaths

Mosa Valley, Belgium 1930 (Firket, 1936)

Donora, PA USA 1948 (Shrenk, 1948)

London, UK 1952 (Ministry of Health, 1987)

China: heavy haze in Beijing, January

2013.

• The association between exposure to particulate matter (PM) and

mortality or morbidity is well established

• Particulate air pollution has been associated with increases in daily

deaths and hospital admissions in many studies across the world

• Air pollution remains a serious, overwhelming problem

Background

Recent Air Pollution Facts

10 Top Risk Factors Ranked by Attributable Burden

of Disease in 2010 (disability adjusted life years)

#3: Household air pollution from solid fuels

#9: Ambient particulate matter pollution

Lim et al., A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters

in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. The Lancet (2012)

Global Public Health Impact

• In 2010, globally:

• Ambient particulate matter pollution accounted for:

– 3.2 million excess deaths

– 3.1% of disability adjusted life years (DALYs)

• Household air pollution from solid fuels accounted for:

– 3.5 million excess deaths

– 4.3% of disability adjusted life years (DALYs)

• Household air pollution is an important contributor to ambient particulate matter pollution

– Account for 16% of the worldwide burden from ambient particulate matter pollution in 2010

Lim et al. Lancet. 2012

Recent Air Pollution Facts

Ratio of estimated 2005:1990 PM2.5 concentrations

Between

1998–2012,

global ambient

PM2.5

concentrations

increased by

2.1% / year

Brauer et al., Environ. Sci. Technol. (2012); van Donkelaar et al., EHP (2015)

Reducing particle pollution

• National Research Council (NRC) stated most important research priorities:

• to set standards for criteria pollutants

• to understand the relationship between particulate matter and public health

• Under the Clean Air Act, US Environmental Protection

Agency (EPA) set National Ambient Air Quality Standard

(NAAQS) for criteria pollutants

– ozone, lead, sulfur oxides, nitrogen oxides, and particulate matter

– periodically revised

What is Particulate Matter?

• "Particulate matter," also known as particle pollution or PM, is a complex mixture of extremely small particles and liquid droplets found in the air.

Common Sources:

• Primary particles are emitted directly from a source: – dust, fuel combustion, motor vehicles, industrial, fires

• Secondary particles formed in complicated reactions in the atmosphere of chemicals emitted from power plants, industries and automobiles.

These particles make up most of the fine particle pollution in the US.

How Big is Particle Pollution?

How small is 2.5 micrometers?

The average human hair is about 70-100 micrometers in diameter – making it 30

times larger than the largest fine particle.

Grouped into size categories:

Inhalable particles (PM10) <= 10 mm in diameter.

Fine particles (PM2.5) are 2.5 mm in diameter and smaller.

Inhalable coarse particles (PM10-2.5) >=2.5 mm and <= 10 mm in diameter

Robert D. Brook et al. Circulation. 2004;109:2655-2671

How Air Quality Affects Health1

Enter body through

the nose and throat

2|3

Larger particles (PM10)

are eliminated

4

PM2.5 penetrate into

the lungs/alveoli

http://www.bcairquality.ca/health/air-quality-and-health.html

Identifying and quantifying the influence of

environmental factors on human disease in

communities to provide scientific evidence for

environmental and health policies.

1. Quantify relationship between air pollution and health

2. Develop mathematical and statistical tools to examine this

relationship

3. Identify subpopulations most susceptible to adverse health

effects from air pollution exposure

4. Study the physiologic mechanisms by which ambient air

pollution mediates adverse health effects

5. Development of models to improve monitoring and exposure

methods.

Existing literature

• Many studies around the world found significant

associations between particulate matter and health

outcomes– all-cause and cause-specific mortality

– cardiovascular & respiratory outcomes

– lung cancer etc

• Short-term exposure (few days)

Acute health effects

• Long-term exposure (few years)

Chronic health effects

Examples studies of

short term PM2.5 effects1. Fine particles (PM2.5) are more harmful to health than larger

particles (PM10)

– Coarse particles (=PM10-PM2.5) are not regulated by U.S. EPA

We test the hypothesis that PM2.5 and PM coarse are

associated with mortality

2. Possible mechanisms of mortality/PM2.5 associations

include: oxidative stress systemic inflammation, and

cerebrovascular dysfunction

– These are related to neurovascular dysfunction and

neurodegeneration

Examine if exposure to PM2.5 increases the risk of

hospitalization for diabetes or neurological disorders

The Effect of Fine and Coarse Particulate Air

Pollution On Mortality: A National Analysis

Map of the 112 US cities included in the study.

Symbol size: the population

Color: PM2.5 concentrations

We conducted a multi-city time series study of the acute effect

of PM2.5 and of PM coarse on the increased risk of death

Zanobetti A & Schwartz J. Environ Health Perspect, 2009;117(6):898-903

Health data

Counts of mortality from NCHS

for years 1999-2005 all cause mortality

cardiovascular disease

myocardial infarction

stroke

respiratory disease

Environmental Data

PM10 PM2.5 ambient monitors from US EPA’s Air Quality System

Technology Transfer Network (EPA

AQS)

-1

0

1

2

3

4

5

6

Percent increase (95% CI) for 10 mg/m3 increase in PM2.5.

Combined results across 112 cities of the mortality PM2.5

association, for the two days mean, sum of 4 days

distributed lag and for the two days mean by season.

PM2.5 PM coarse

% 95% CI % 95% CI

All cause

mortality 0.77 0.43 1.12 0.47 0.21 0.73

CVD 0.61 0.05 1.17 0.29 -0.04 0.61

MI 0.75 -0.12 1.63 0.04 -0.72 0.81

STROKE 0.82 -0.21 1.86 0.71 0.02 1.41

Respiratory 1.63 0.69 2.59 1.14 0.43 1.85

Percent increase in mortality for 10 µg/m3 increase

in PM coarse and PM2.5 for the two days mean,

across the 47 cities: two- pollutant model. Increased risk of mortality for all and specific causes

associated with PM2.5 and with PM coarse

The risks are higher than what previously observed for PM10.

Health Data Medicare data for citizens >65 years

Hospitalizations:

Dementia (N=717,000)

Alzheimer's disease(N=1,335,000)

Parkinson’s disease (N=714,000)

Multiple sclerosis(N=66,000)

Diabetes(N=8,245,000)

Deaths (N=6,983,000)

Environmental DataPM2.5 from US EPA AQS

2 days average

Map of the 121 US cities

A national case-crossover analysis of the short-term effect

of PM2.5 on hospitalizations and mortality in subjects with

diabetes and neurological disorders.

Zanobetti A, et al. Environ Health 2014;13(1):38.

1. The association between short-term exposure to PM2.5 and all-cause mortality is

modified by having a previous hospitalization of diabetes or neurological disorders.

2. Exposure to PM2.5 increases the risk of

hospitalization for diabetes or neurological

disorders

Percent Increase in mortality and admissions

for 10 mg/m3 Increase in the 2 Days Average PM2.5% 95% CI

1) Mortality

All deaths 0.64 0.42 0.85

Deaths without medical conditions 0.60 0.36 0.84

Mortality by Previous Cause of Hospitalization

Alzheimer's disease 1.04 0.36 1.72

Dementia 0.94 0.01 1.89

Parkinson's disease 1.15 0.09 2.23

Multiple Sclerosis 4.01 -0.03 8.21

Diabetes 0.76 0.39 1.12

2) Cause Specific Hospitalizations

Alzheimer's disease 0.20 -1.26 1.69

Dementia 0.92 -0.44 2.30

Parkinson's disease 3.23 1.08 5.43

Multiple Sclerosis 0.52 -5.36 6.77

Diabetes 1.14 0.56 1.73

Examples studies of

long term PM2.5 effects

1. Increased interest in the effects of air pollution on the

central nervous system and neurodegeneration

Examined the potential effect of long-term PM2.5 exposure on first

admission for dementia, Alzheimer’s or Parkinson’s diseases

2. To identify spatial locations and population sub-groups that

are more vulnerable to the effects of the exposure

We assessed whether community-level variables, including

socioeconomic status (SES) indicators, increased urbanicity and

temperature modify the association between long term exposure to

PM2.5 and mortality.

Long-term PM2.5 Exposure and Neurological

Hospital Admissions in the Northeastern US

Health Data Medicare enrollees (1999-2010)

9.8 M subjects

> 266K Alzheimer’s (AD)

> 119 K Parkinson’s (PD)

Mean age: 76.6 yr (SD: 7.6),

57.3% female, 80.4% white

Environmental DataPM2.5 from US EPA AQS Annual averages

50 cities across 12 Northeastern States

Kioumourtzoglou MA et al. EHP 2015

Assess the potential impact of long-term PM2.5 exposure on event time,

defined as time to the first admission for dementia, Alzheimer’s or

Parkinson’s diseases

Findings

• City-specific Cox proportional hazard models– No confounding across cities, by long-term trends or individual

characteristics

Per 1 μg/m3 annual PM2.5:

• Alzheimer’s Disease: HR = 1.15 (1.11, 1.19)

• Parkinson’s Disease: HR = 1.08 (1.04, 1.12)

• One of the first study to examine the relationship between long term exposure to PM2.5 and time to the first hospitalization for the most common neurodegenerative diseases.

• Our findings provide the basis for more studies, as the implications to public health can be crucial.

Long-term exposure to PM2.5 and mortality in 207

US cities: Modification by temperature, population

characteristics and green space

• City-level characteristics:

• Census:– median household income – % in poverty – % of white, black and Asian – % of residents with and without

high-school degrees and with a college degree

Health Data >35M Medicare enrollees (1999-2010)

Observed >11M deaths

Environmental DataPM2.5 from US EPA AQS

Annual averages

• Smart Growth America: Urbanicity

• Behavioral Risk Factor

Surveillance System:• city-specific smoking (2000–2010)

• obesity rates (2004–2010)

• Normalized Difference Vegetation

Index (NDVI).• Greenness Kioumourtzoglou et al., Epidemiology 2015

Effect modification on the PM2.5–mortality association,

HRs per 10 μg/m3 at the 25th and 75th % of each variable

Living in cities

with low SES

is associated

with higher

effect

estimates.

HR = 1.19 (1.11, 1.28) per 10 μg/m3 annual PM2.5

Largest

national study

for long-term

PM2.5 and

mortality

Issues in existing studies

• Long-term and short-term exposure to fine particulate

matter has been consistently associated with adverse

health

• Previous studies have generally focused on:

– Either long-term or short-term exposures

– Exposure across the entire range of PM2.5 concentrations

– Use monitored data

Issues in existing studies

• Rural areas are not generally represented

• Spatial variability in PM2.5 concentrations within cities not

taken into account, which can introduce exposure

measurement error

• No simultaneous estimate of long-term and short term

effects

• Relevant to future assessments of current U.S. EPA

standards

– Health effects when air quality concentrations are at or below

the existing NAAQS levels

Moving forward

1. Improve exposure assessment

2. Estimate health effects when air quality

concentrations are at or below the existing or

alternative NAAQS levels

– U.S. EPA review NAAQS every 5 years

– Idea is that if significant effects are seen at lower level of

the existing NAAQS, there is support for the NAAQS not

being adequate to protect public health

Improving Exposure assessment• Monitoring stations:

• Usually average across available monitoring stations in a county• Represent the average exposure concentration for all population• Temporal variation

• Land Use Regression models• Uses spatial patterns of land use, such as population density, distance to

roads, etc. to predict PM measurements at monitoring stations and apply the predictions elsewhere

• To assess long–term exposure

• Provide good estimates of spatially resolved long-term exposures, but are poor at capturing short term exposures

• Spatial variation

• Spatio-temporally resolved predictions

Spatio-temporally resolved predictions

• Include both spatial and temporal

variables

ground PM2.5 measurements

land use regression variables

meteorological variables

Satellite-based remote sensing data on

aerosol optical depth (AOD).

Kloog I, et al. Atmospheric Environment, 2011, 45, 35, p. 6267-6275

• Novel spatio-temporally resolved predictions PM2.5

concentrations at the grid level (1km x 1km)

• Daily predictions (short and long term exposure)

Low-Concentration PM2.5 and Mortality:

Estimating Acute and Chronic

Effects in a Population-Based Study

• The present study aimed to:

1. Simultaneously estimate acute and chronic health

effects of PM2.5 in a population-based cohort (≥ 65

years of age) in New England region

2. PM2.5 satellite based predictions

3. Estimate the effects of low-concentration PM2.5 on

mortality

Shi L, et al. Environ Health Perspect 124:46–52, 2016

Data

Health Data Medicare enrollees (2003-2008)

• Daily count of death for each ZIP code

Environmental Data

PM2.5: Spatio-temporally resolved predictions

Short term exposure (2-day average, lag01)

Long term exposure (365-day moving avera

ge)

Restricted to annual concentrations below

10 µg/m3 or daily concentrations below

30 µg/m3

Mean PM2.5 concentrations in 2004 at a

high resolution (1 km x 1 km) across New

England predicted by the AOD models

Percent increase in mortality for a 10 µg/m3

increase for PM2.5

Shi et al., EHP,2015

PM2.5 exposure type Model Percent increase p-value

Short-term PM2.5 exposure Low daily exposure a 2.14 (1.34,2.95) <.001

Full cohort 2.14 (1.38,2.89) <.001

Long-term PM2.5 exposure Low chronic exposure b 9.28 (0.76,18.52) 0.032

Full cohort 7.52 (1.95,13.40) 0.007

Using a mutually adjusted model, we found that short- and long-term

exposure to PM2.5 were associated with all-cause mortality, even for

exposure levels not exceeding the newly revised U.S. EPA standards

a Restricted only to person time with daily PM2.5 less than 30 µg/m3.b Restricted only to person time with chronic PM2.5 less than 10 µg/m3.

Below daily PM2.5 NAAQS (35 µg/m3) Below annual PM2.5 NAAQS (12 µg/m3)

Dose-response relationship for low-

concentration PM2.5 and mortality

• Adverse health effects occur at low levels of fine particles

• Improving air quality below the current PM2.5 NAAQS can

still yield health benefits

Conclusion• Based on the literature there is a causal effect of short-term

exposures to PM2.5 and mortality

• Strong evidence for other outcomes and for chronic exposure

Moving Forward• Changes in the standards require additional studies to

elucidate whether health effects occur at levels below the current annual and daily U.S. EPA NAAQS of 12 and 35 μg/m3

• More studies estimating acute and chronic effects of cardiovascular morbidity outcomes associated with short and long-term exposure to PM2.5, in both rural and urban areas, and at low concentrations.

Acknowledgments

Joel Schwartz, Diane Gold, Petros Koutrakis

Francesca Dominici, Brent Coull

Marianthi-Anna Kioumourtzoglou, Itai Kloog

Marc G. Weisskopf, Liuhua Shi

Clean Air Research Center

(CLARC) RD 83479801

834900

Harvard-NIEHS Center for Environmental Health P30ES000002

R21 ES024012, R01 ES024332

THANK YOU!