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Indoor and Outdoor Air Pollution
Jonathan M. Links, PhDJohns Hopkins University
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Section A
Introduction and Background
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What Are the Problems?
A person inhales approximately 30 m3
(or 35 pounds)of air per day
− Roughly 6 times more than the food and drink
consumed per day
Exposure to air pollutants is continuous (and, usually,
involuntary)
Lung disease is the third leading cause of death in the U.S.
(~335,000 deaths per year)
Asthma is the most common chronic illness in children
− Leading cause of hospital admissions of children
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Types of Air Pollutants
Natural Particulate matter
− Volcanic ash
−
Radioactivity− Pollen dust
− Smoke from fires
Man-made Gaseous
− Derived from combustion processes
−
Hydrocarbons− Oxides of sulfur and nitrogen compounds
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Types of Air Pollutants
Particulate matter− Solid or aqueous particles
0.01 to 100
−
Smallest particles (aerosols) can remain suspended− Below ~ 2.5 are capable of penetrating all sites of the
respiratory tract
Carbonaceous dust, metallic oxides, salts, or acids Porosity such that they absorb or adsorb other gases,
liquids, and solids
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Some Common Types of Particulate Matter
Aerosols− Any tiny solid or liquid particle
Dusts
−
Solid particles from grinding or crushing Fumes
− Solid particles occurring when vapors condense
Mist, fog− Liquid particles
Smoke, soot, ash
−
Solid particles, mostly carbon, from combustion Smog
− Any air pollutant; originally meant smoke plus fog
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The Clean Air Act (CAA): Underlying Philosophy
Everybody should have the same degree of protection− Establish uniform national standards
Most susceptible subgroups of individuals (e.g., asthmatics,
children) are to be protected−
Element that drives much of the biomedical research
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CAA Classification of Air Pollutants
“Criteria” pollutants− Ubiquitous (wide-spread)
− Not very toxic
−
PM, SO2, NO2, O3, CO, Pb
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CAA Classification of Air Pollutants
Hazardous air pollutants (HAPs)−
Sources may be limited and industry specific
− More toxic and even carcinogenic
−
~188 chemicals− For example, benzene, formaldehyde, cadmium, vinyl
chloride
Separate strategies exist for regulating criteria and hazardouspollutants
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Criteria Pollutants
Emitted from many large diverse sources, including mobileand stationary sources
Omnipresent and, therefore, pose the greatest overall threat
to human health
Assumption: the adverse health effects are not cancerous,
and their dose-response relationship exhibits a threshold
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National Air Pollution Emissions, 1998
0
20,000
40,000
60,000
80,000
100,000
NOx VOCs SO2 PM-10 CO
Emissions
T o n s p e r y e a r
Source: EPA.
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Hazardous Air Pollutants (HAPs)
1990 CAA amendment specified 188 pollutants or chemicalgroups
HAPs are more toxic than criteria pollutants; they “. . . may
reasonably be expected to result in serious irreversible . . .
disease, including cancer”
Examples
− Heavy metals (chromium, mercury)
−
Organics (benzene, perchloroethylene)
P S
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HAP Sources
61%
Point sources
21%Mobile
sources
Area sources (non-point sources)
– Dry cleaning operations
– Solvent cleaning
– Secondary lead smeltersand chrome plating
– Commercial
sterilizers
18%Area
sources
Point sources
– Large industrial
complexes
– Chemical plants
– Oil refineries
– Steel mills
– Aerospace
manufacturers
– Marine tank vesselloading
T f i d L R T f HAP
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Transformation and Long-Range Transport of HAPs
SourcesMobile
Stationary
Natural
Primary PollutantsSO2, NO2, CO, PM
Secondarily Formed
PollutantsO3, acid aerosols
Man-made
Chemical
transformation
in atmosphere
S d E i i f P i Ai P ll t t
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Sources and Emissions of Primary Air Pollutants
Sources Emissions
Transportation
46%CO
48%
Fuelcombustion
(stationary
sources) 29%
Industrial
processes 16%
SO216%
NOx
16%
VOCs
15%
Particulates
5%
Solid waste
disposal 2%Miscellaneous
7%
T f ti f Ai P ll t t
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Transformation of Air Pollutants
Ozone formation
Fine particle formation (droplet aerosols)
Hydrocarbons
(VOCs) NO2 O3
SO2(gas)
H2SO4(particle)
+Sunlight
Atmospheric
oxidation
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Accumulation of Pollutants
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Accumulation of Pollutants
As air moves across the continent from west to east, eachpopulation area adds to the total pollution in the atmosphere
Source: Adapted by CTLT from Boyce, A.
Normal Pattern
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Normal Pattern
Source: Adapted by CTLT from Mackenzie, F.T.
Inversion Layer
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Inversion Layer
Source: Adapted by CTLT from Mackenzie, F.T.
Aerosol Formation
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Aerosol Formation
H2SO
4(sulfates) and O
3cross state and national jurisdictions
Acid sulfates and O3 are often together, temporally and
spatially
Source: Adapted by CTLT from Boyce, A.
Dry and Wet Deposition of Air Pollutants
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Dry and Wet Deposition of Air Pollutants
Source: Adapted by CTLT from Kemp, D. D.
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Section B
Health Effects
Aerodynamic Behavior of Aerosols
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Aerodynamic Behavior of Aerosols
Solid particle origin, size distribution, composition, and air-
borne residence time
Subdivisions of the Conducting Airways
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Subdivisions of the Conducting Airways
Schematic
representationfor the subdivisions of
the conducting airways
and terminal
respiratory units
Source: Adapted by CTLT from Murray.
Particle Size and Deposition within the Respiratory Tract
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Particle Size and Deposition within the Respiratory Tract
Particle sizes for
common air
pollutants and
the sites of their deposition within
the respiratory
tract (assuming arespiratory rate of
15/min and a tidal
volume of 750 ml)
Source: Adapted by CTLT from Blumenthal, D. S.
Three Mechanisms of Aerosol Particle Deposition
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Three Mechanisms of Aerosol Particle Deposition
Schematic representation of the three main mechanisms of
aerosol particle deposition
Particle Deposition in the Lung
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a t c e epos t o t e u g
Particlesize
Respiratoryrate
Depositionprocess
Depositionsite
Coarse High Impaction Largeairways
Coarse Low Sedimen-
tation
Large and
smaller airways
Fine High Diffusion Large and
smaller airways
Fine Low Diffusion Alveoli
Numbers and Surface Areas of Monodispersed Particles
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p
Numbers and surface areas of monodispersed particles
of unit density of different sizes at a mass concentration
of 10 g/m3
ParticleDiameter
ParticleNumber perm3 [x106]
ParticleSurface Area(m2/m3 air)
[x106]0.02 2,400,000 3,016
0.1 19,100 600
0.5 153 1201.0 19 60
2.0 1 24
Health Effects Associated with Air Pollution
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Acute
−Loss of lung function (FEV1 by spirometry)
− Disability (absenteeism, increased need for medication,
increased emergency room visits, hospitalization)
−
Increased mortality rate (respiratory and cardiovascular
deaths)
− Symptoms of irritation (cough)
Chronic
− Impaired lung growth (spirometry)
− Accelerated lung aging (spirometry)
−
Damage to other organ systems
Cancer
Criteria Pollutants: Method of Control
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National ambient air quality standards (NAAQS)
Level of protection
− “. . . adequate margin of safety”
To protect against effects that have not yet been
uncovered by research, and effects whose medical
significance is a matter of controversy
To be set low enough to protect the health of all
susceptible groups within the population
Susceptibility
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p y
0
100
P e r c e n t a g e o f
P o p u l a t i o
n
R e s p o n
d i n g
Threshold Dose Dose
susceptible
resistant
Criteria Pollutants and Susceptible Subpopulations
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SO2
−Persons with increased airway reactivity (asthmatics)
CO
− Persons with arteriosclerotic disease affecting coronary
vessels (angina patients)
Pb
− Fetuses and children
Criteria Pollutants and Susceptible Subpopulations
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PM10
−Mortality—the elderly with cardiovascular and pulmonary
disease
− Morbidity—children
NO2− Children (respiratory illness)
O3
−
Active people
HAPs: Method of Control
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Because they may exhibit no threshold, air quality standards
would be inappropriate; instead, site-specific emission
standards are established
The emission standards must provide an ample (not simply
adequate—as with the criteria pollutants) margin of safety
− Note: Ample is also ambiguous, but more demanding
than adequate
Has the CAA Been Effective?
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0
25
50
75
100
125
150
CO NOx VOC PM-10 SO2
1970 1995
-28%
+6% -25%
-79%
-41%
Lead: -98%
M i l l i o n S h o r t
T o n s / Y e a r
Notes Available
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Section C
Indoor Air
Indoor Air Pollution: Reasons for Special Concern
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~75–90% of time spent indoors
− Time depends on season, age, gender, health status
Many air pollutants known to be hazardous to health are
emitted indoors
Indoor environments trap pollutants
− Levels may be 2 to 5 times higher than outside
Air Inside a Building Can Be Polluted as a Result of
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Energy conservation measures
−
“Air tightening” of buildings
− Ventilation standards lowered
Building occupancy
Human activities inside the structure
Gas-off from synthetic building materials
Reliance on forced air ventilation systems
Air Inside a Building Can Be Polluted as a Result of
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Biogenic pollutants
−
Aeropathogens
− Aeroallergens
Infiltration from outdoors
−Molds and fungi, combustion sources, animal dander,
outdoor air pollution
Reactivity of pollutants
Poor housing conditions
− Vermin and pests
Sources of Indoor Air Pollutants
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Sources Pollutants
Soil and groundwater Radon and radioactiveprogeny
Building materials and
furnishings (carpeting, paint,
varnish, adhesives)
Formaldehyde, asbestos, vinyl
chloride, organic fumes
Personal activities and
hobbies
Cigarette smoking, fireplace
smoke, solvent and glue
fumes
Appliances, cooking, and
heating
Carbon monoxide, natural gas,
cooking odors, boiler and
heater fumes
Notes Available
More Sources of Indoor Air Pollutants
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Sources Pollutants
Household chemicals (bleach,oven cleaner, insect sprays,
nail polish, hair spray)
Ammonia, hydrogen chloride,pesticides, organic fumes,
aerosols
Electronic equipment and
wiring
Organic fumes,
electromagnetic radiation
Pets Hair, feces, proteins, dust
Plants Pollen, hydrocarbons
The Stack Effect
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44 Adapted by CTLT
Air Pollution in the Home
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45 Adapted by CTLT from Boyce, A.
Air Exchange Rate
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Rate at which air is replaced in the structure by external air
−
Average for American home: 0.7 to 1.0
air changes per hour
− Tightly sealed homes without provisions for and
exchange: ~0.2 air changes per hour
Make-up air (from outside)
− Before 1973: 15 cubic feet per minute (cfm) per person
−
After 1973: 5.0 cfm per person
Environmental Tobacco Smoke (ETS)
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47 Adapted by CTLT
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Tobacco Smoke, Women, and Lung Cancer
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Lung cancer in women according to the presence of direct
and involuntary smoking
Standard mortality rate for lungcancer per 100,000 persons per year
0 10 20 30 40
Nonsmoking women with
nonsmoking husbands
Nonsmoking women, husbandssmoke 1–19 cigarettes per day
Nonsmoking women, husbandssmoke more than 20 cigarettes per day
Smoking women
Source: Adapted from Hirayama, T. (January 1981). British Medical Journal, 282.
Field Survey of Indoor RSP
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Field survey of indoor respirable suspended particulates (RSP)
LocationNumber of
occupants
Number of
smokers
Indoor RSP
( g/m3)
Outdoor RSP
( g/m3)
Cocktail party 14 2 350 –
Lodge hall 350 40 700 60
Bar and grill 75 9 590 63
Pizzeria 50 5 415 40
Church
Bingo game
Services
150
300
20
0
280
30
–
–
Bowling alley 128 14 200 50
Hospital
waiting room19 2 190 58
Source: Repace, J. L. and Lowrey, A. H. (May 2, 1980). Indoor air pollution, tobacco smoke, and public health.
Sciences, 208. Copyright 1980 by the AAAS.
ETS Particle Size Distribution
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Comparison of Air Pollutant Emissions
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Comparison of air pollutant emissions from energy equivalent
fuels (kg)
Fuel PM SOx NOx HCO CO
Wood 2,170 86 110 1,450 18,790
Coal 520 1,200 270 430 2,380
Oil 11 1,170 71 4 20
Gas 7 Neg. 38 4 10
Notes Available
Role of Biofuels in Cooking and Heating
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53Source: Smith, K. R.
Emissions of TSP in Small Stoves for Various Biofuels
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Emission of total suspended particulates (TSP) in small open
cook stoves for various biofuels
0 10 20 30 40
Coconut husk and shell
Cow dung
Wood and cow dung
Wood
Total suspended particulates (g/kg)
Source: Smith, K. R.
Indoor Air Pollution from Biomass Combustion
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Location Measurement period
Concentration of TSP
as multiple of WHO
peak guidelines
China Cooking 11
Gambia Average over day 4–11
India Cooking 16–91
Kenya Space heating (o.n.) 12–34
Nepal Cooking 9–38
Papua Space heating (o.n.) 5–39
Source: Smith, K. R.
Sources of VOCs in Indoor Air
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Category Examples Emissions
Construction materialsFoam insulation, carpet glue,
paint
Methyl chloroform,
formaldehyde, styrene, xylene,
tetrachloroethylene, benzene,
1,1,1-trichloroethane
Structural componentsParticle board, vinyl tile,
sheetrock
Formaldehyde, xylene, acetone,
benzene, n-decane, benzyl
chloride
Furnishings
Foam, textured carpet, drapery,
upholstered fabric
Formaldehyde, methyl
chloroform, benzene,
tetrachloroethylene, 1,1,1-trichloroethane
Cleaners and solvents
Liquid detergent, chlorine
bleach, scouring powder,
furniture wax
Xylene, n-dodecane, benzene,
chloroform, n-undecane, n-
decane, 1,1,1-trichloroethane
Personal care productsEyeliner pencil, deodorant, skin
lotion
Methyl chloroform, styrene,
tetrachloroethylene, benzene,
isoprene
Combustion Wood, keroseneAcrolein, formaldehyde, 1-
nitropyrene, 1-nitronapthalene
Source: Samet, J.
Selected VOCs in Indoor and Outdoor Air
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Benzene
Styrene
0 5 10 15 20
Indoors Outdoors
Chloroform
Tetrachloroethylene
Trichloroethane
CCL4
Micrograms per cubic meterSource: Data from (February 1998). Scientific American.
Selected Indoor Aeroallergens and Aeropathogens
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Bacteria
−
Staphylococcus aureus
− Legionella
− Escherichia coli
−
Salmonella spp.
− Pseudomonas aeruginosa
− Mycobacter. tuberculosis
−
Klebsiella pneumoniae
Source: Samet, J.
More Indoor Aeroallergens and Aeropathogens
Y
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Yeasts
−
Candida albicans
− Saccharomyces cerevisiae
Viruses
Fungi
− Aspergillus niger
− Penicillium funicolosum
−
Trichophyton spp.
Amoeba
Arthropods
−
Mites, cockroaches
Dander
− Cat, dog, hamster
Regulatory Jurisdictions
O d i EPA l i (CAA)
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Outdoor air: EPA, clean air act (CAA)
Occupational air: OSHA
Indoor air (apart from occupational air)
− No specific federal laws
−
State and local jurisdictions regulate air quality in public
buildings
Standards in ventilation and air exchange rates
Controlling activities (e.g., smoking)
Limit use of products that affect air quality
Private residence
−
Must rely on education
Strategies to Control Indoor Air Pollution
V til ti
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Ventilation
Source removal
Source modification
Air cleaning (pollutant removal)
Education
Building-Related Illness
Di t id tifi bl di ill
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Discrete, identifiable disease or illness
Can be traced to a specific pollutant or sources within abuilding
Cough, chest tightness, fever, chills, muscle aches, or more
serious outcomes Legionnaires’ disease, hypersensitivity pneumonitis,
humidifier fever
Sick-Building Syndrome (SBS)
Set of symptoms associated with time spent in building
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Set of symptoms associated with time spent in building
−
Respiratory tract irritation, skin irritation, headache,dizziness, nausea, fatigue, concentration problems
Symptoms diminish or cease when occupants leave the
building Cannot be traced to specific pollutants or sources within the
building
Related to multiple chemical sensitivity (MCS)
Key Points: Outdoor Air Pollutants and Health Effects
Major outdoor air pollutants are O SO NO Pb CO PM
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Major outdoor air pollutants are O3, SO2, NO2, Pb, CO, PM
They are either directly emitted into outdoor air (primarypollutants) or formed in the air via chemical reactions
(secondary pollutants)
Adverse health effects include acute reduction of lungfunction, respiratory or cardiovascular deaths, and cancer
Key Points: Criteria
Setting of criteria includes pollutants that:
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Setting of criteria includes pollutants that:
−
“May reasonably be expected to endanger public healthand welfare”
− Must reflect the latest scientific information
−
Must allow for an adequate margin of safety− But cannot consider cost
Key Points: Indoors
We spend up to 90% of our lives indoors
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We spend up to 90% of our lives indoors
The indoor environment contains many toxicants, eitherbecause they’re emitted indoors (e.g., VOCs or ETS) or
because they’re trapped due to energy conservation
measures (e.g., respirable particles or radon)
Key Points (Continued)
ETS is a major source of toxic and carcinogenic agents that
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ETS is a major source of toxic and carcinogenic agents that
are less completely combusted in SS than in MS smoke Building-related illness has traceable etiology, whereas sick-
building syndrome and multiple chemical sensitivity do not