Transcript AP Lecture

Woodsmoke and Human Health
Ryan W. Allen, PhD
Associate Professor
Faculty of Health Sciences
Simon Fraser University
Burnaby, BC, Canada
[email protected]
National Educational Forum on the Residential Wood Heater NSPS
November 8, 2012
Minneapolis, MN
Presentation Overview
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What are the exposure/public health impacts
of woodsmoke?
At what levels and duration of time are there
health impacts?
Some general comments on air pollution and health
How does woodsmoke differ from pollution
generated by other sources?
Woodsmoke and health
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What do we know? What don’t we know?
Emphasis from studies in developed countries
Range of health effects and exposure-effect time scales
Air Pollution Epidemiology
Requires an Exposure Gradient
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Temporal or spatial (or both)
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Temporal gradients
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Hours to days
Provide information on “acute” effects
of air pollution
Example: On days with more air
pollution, more people die
(“triggering”)
Spatial gradients
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M to 1000s of KM
Provide information on “chronic”
effects of air pollution
Example: People living in more
polluted areas of a city die younger
than those in less polluted areas
(underlying disease?)
Daily PM2.5
Concentration
Day
Count of Daily
Deaths
Day
Air Pollution and Health
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Air pollution influences a wide
range of health outcomes and
severities
Historical focus on respiratory
effects
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Now also strong evidence of
cardiovascular effects
Growing evidence of other impacts
(e.g. birth effects)
Individual risks are small, but
many are exposed, so
population impacts can be
substantial
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Example: air pollution vs. smoking
Mortality
Hospital admissions
Severity
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Emergency visits
Functional limitation
Symptoms
No adverse
health effect
Frequency
How is Woodsmoke Different?
inhalation intake fraction 
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mass inhaled
mass emitted
Residential Woodsmoke Intake Fraction
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Vancouver study
13 – 15 per million
Similar to vehicle emissions
~7x higher than all-source PM
Reis, Brauer et al., 2009
How is Woodsmoke Different?
• Compared dose of deposited particles in airway for traffic exhaust
and residential wood combustion particles.
• Subjects breathed concentrations of 100 µg/m3
• Traffic particle dose was 16x by number, and 3x by surface area.
WHY?
• Traffic particles have:
• Higher deposition probability
• Higher particle number and surface area per mass concentration
Particle toxicity influenced by size, composition, physical
properties, etc.
Londahl et al., 2008, 2009
Woodsmoke and Health: Evidence
• Epidemiologic Evidence:
“…..epidemiologic studies of indoor and community exposure
to biomass smoke indicate a generally consistent relationship
between exposure and increased respiratory symptoms,
increased risk of respiratory illness, including hospital
admissions and emergency room visits, and decreased
lung function. Several studies suggest that asthmatics are
a particularly susceptible subpopulation with respect to
smoke exposure….”
Naeher et al., 2007
Woodsmoke and Health: Evidence
• General Conclusions
“...at the present time fine particles may represent
the best metric to characterize exposures to smoke
from residential wood combustion...”
“There is no persuasive evidence that woodsmoke
particles are significantly less dangerous for
respiratory disease than other major categories of
combustion-derived particles in the same size range.”
“There is too little evidence available today,
however, to make a judgment about the relative toxicity
of woodsmoke particles with respect to cardiovascular
or cancer outcomes.”
Naeher et al., 2007
Woodsmoke and Health: Evidence
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Constituents
Toxicology
Biomass burning in developing countries
Forest fires
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Firefighters
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Impacted communities
Communities impacted by agricultural burning
Controlled human exposure studies
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Limitation: only acute, reversible effects
Communities impacted by residential
woodsmoke
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Challenge: often small communities
Sarnat S. et al., JAWMA, 2006
(limited statistical power)
Some Woodsmoke Constituents
Constituent
Properties
Particulate Matter (PM2.5) Inflammation, oxidative stress
Carbon Monoxide
Asphyxiant
Nitrogen Dioxide
Irritant
Benzene
Carcinogen*, mutagen
PAHs
Carcinogen*, mutagen
Aldehydes
Irritant, carcinogen*, mutagen
Phenols
Irritant, carcinogen*, mutagen, teratogen
Adapted from Larson & Koenig, 1994; Naeher et al., 2007
*Indoor emissions from household combustion of biomass fuel (primarily
wood) are categorized as a Group 2A carcinogen (probably
carcinogenic to humans – limited human evidence with supporting
animal evidence) by the International Agency for Research on Cancer
(IARC).
Indoor Biomass Smoke
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Indoor biomass (wood, crops) and
coal smoke:
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3 billion exposed
1.6 million premature deaths
2.7% of global burden of disease
Strong evidence for:
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MUCH HIGHER
EXPOSURES THAN IN
DEVELOPED WORLD
Respiratory infections
Obstructive lung disease (women)
Low birth weight
Cataracts
Limited evidence for:
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Tuberculosis
Asthma
Otitis media
Lung cancer (biomass)
WHO, Fuel for Life, 2006
Controlled Exposure Experiments
Barregard et al., 2006
Controlled Exposure Experiments
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13 subjects exposed
to wood smoke and
clean air
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240–280 μg/m3
4-hour sessions, 1
week apart
Barregard et al., 2006
Air Pollution and Hospital
Admissions in Christchurch, NZ
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“Uniquely in Christchurch, more than 90% of particulate air
pollution has been estimated to come from the city’s 47,000
wood burners and open fires that are used during the cold
winters months”
McGowan et al., 2002:
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3.37% increase in respiratory admissions and 1.26%
increase in cardiac admissions per 15 µg/m3 outdoor
PM10
Barnett et al., 2006:
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No significant effects of PM10 on cardiac admissions
Sarnat S. et al., JAWMA, 2006
McGowan et al., ANZJPH, 2002; Barnett et al., EHP, 2006
Intervention Studies
HEPA Filtration
“Placebo” Filtration
Health
Measurements
Health
Measurements
Monitoring Session 1
Monitoring Session 2
Monitoring Session 1
Monitoring Session 2
Random
Selection
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45 participants, 25
homes in Smithers, BC
Portable HEPA filters
60%  in indoor PM2.5
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Day 0
Technician
Visit
Day 7
Technician
Visit
Day 14
Technician
Visit
11.2  4.6 ug/m3
Increases in endothelial
function and decreases
in systemic inflammatory
markers
Allen et al., AJRCCM 2011
Intervention Studies
Libby, Montana stove exchange
• ~30% reduction in winter PM2.5
•  in childhood wheeze, itchy eyes, sore throat, cold, bronchitis,
influenza, throat infections
• School absence associations inconsistent
Noonan et al., HEI Report 162, December 2011
Mapping Woodsmoke in Vancouver
Mobile Monitoring on Cold,
Clear Winter Evenings
(~ 12,000 points)
Lowest third
Middle third
Highest third
Larson et al. Environmental Science and Technology. 2007
Reis et al, Environmental Science and Technology. 2009
Vancouver Results
Outcome
Exposure
window
N
Design
(n cases)
Mean
Days
exposed
[IQR]
Adjusted# OR
(95% CI)
SGA birth
All pregnancy
70,249
(6,939)
Cohort
65 [43]
1.00 (0.91 - 1.09)
Asthma3
(0 – 48 mos.)
All pregnancy
37,401
(3,482)
Nested
C-C**
60 [33]
1.00 (0.94 - 1.07)
89 [17]
1.00 (0.98 - 1.02)
Bronchiolitis1
2 – 12 months
86,337
(10,485)
Nested
C-C*
54 [45]
1.08 (1.04 - 1.11)
Otitis Media2
(1 – 24 mos.)
1 month prediagnosis
45,513
(19,115)
Cohort
15 [16]
1.32 (1.27 - 1.36)
0 -12 months
per IQR increase, adjusted for covariates: Infant sex (SGA, B, OM) First Nations Status (SGA, B, OM), Parity (SGA, B, A), Maternal
age (SGA, B, OM), Maternal smoking during pregnancy (SGA, B, OM), Month-year of birth (SGA), maternal initiation of breastfeeding
at birth (B, OM, A), Income (SGA, B, OM, A), Maternal education (SGA, B, OM, A), older siblings (OM), birth season (OM),
birthweight (OM, A), gestational duration (OM, A). *incidence-density matching (up to 1:10) on date of birth **matched 1:5 by
sex, month-yr of birth
1Karr et al., AJRCCM 20009; 2 MacIntyre et al., Epidemiology 2011; 3Clark et al., EHP
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Summary
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Biomass smoke contains many pollutants with
known adverse effects on health
Woodsmoke is an important source of air pollution
in many communities
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For respiratory outcomes, no evidence that
woodsmoke particles are less dangerous than other,
similarly-sized particles
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Emissions in populated areas  high “intake fraction”
Short-term (≤24 hour) effects on symptoms, lung
function, admissions, & ED visits
Cardiovascular evidence is mixed (controlled
exposure & in-home studies vs. population studies)
Emerging evidence that spatio-temporal variations
in woodsmoke relate to important effects in children
[email protected]
Kocbach Bølling et al. 2009
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