Overview of air pollution

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Overview of air pollution

• A/Prof Bin Jalaludin
• MBBS, MPH, PhD, MRCP (UK), FAFPHM
• South Western Sydney Area Health Service, and
• University of New South Wales

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This talk

• Will give an overview of air pollution
• Will mainly focus on the common outdoor air
  pollutants
• Will discuss types of air pollutants
• Will discuss sources of air pollutants
• Will discuss health effects of air pollution

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Air pollution the problem

• Global
• Ozone layer depletion
• Greenhouse effect
• Regional
• Acid rain
• Haze and photochemical smog
• Local
• Indoor (homes, factories, offices)

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Air pollution the problem
5
Effects of human activities on the atmosphere
(NSW SOE 2000)
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Ozone Layer Depletion

• Stratospheric ozone reduces harmful UV radiation
• Chloroflurocarbons (CFCs), methyl chloroform,
  carbon tetrachloride, halons, methyl bromide
• Montreal Protocol on Substances that Deplete the
  Ozone Layer

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The vertical distribution of ozone in the
atmosphere at mid-latitudes (Commonwealth SOE
2001)
Source after WMO (1999)
8
Postulated steps from the release of halocarbons
to increase in UV related biological damage
Halocarbons release chlorine and bromine
radicals
1
Chlorine and bromine radicals destroy ozone
molecules
2
Stratospheric ozone layer depleted
3
Increase in ultraviolet irradiance at ground level
4
Increase in ultraviolet-related biological damage
Source McMichael 1993
9
Average stratospheric ozone concentrations for
the month of October (NSW SOE 2000)
Source Bureau of Meteorology data, as at 1999
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Concentrations of ozone-depleting substances,
Cape Grim, Tasmania (NSW SOE 2000)
Source CSIRO data, as at 1999
11
Past and future stratospheric chlorine levels
(ppb, cumulative) of the major ozone-depleting
substances (Commonwealth SOE 2001)
Source Madronich and Velders (1999).
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Greenhouse Gases

• Naturally occurring gases - CO, methane
• Anthropogenic gases CO2, nitrous oxide,
  chlorofluorocarbons (CFCs)

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Source CSIRO Atmospheric Research.
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Source Bureau of Meteorology
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Global warming potentials of greenhouse gases
Potentials are expressed as a multiple of the
global warming potential of carbon dioxide.
(Commonwealth SOE 2001)
16
Carbon dioxide concentrations, Cape Grim,
Tasmania (NSW SOE 2000)
Source CSIRO data, as at 2000
17
Methane concentrations, Cape Grim, Tasmania (NSW
SOE 2000)
Source CSIRO data, as at 2000
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Nitrous oxide concentrations, Cape Grim, Tasmania
(NSW SOE 2000)
Source CSIRO data, as at 2000
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Acid Rain

• Emissions of oxides of sulphur and nitrogen
  produce Acid Aerosols - H2SO4, HNO3 (also
  regional pollutant)
• Coal fired (and oil fired) power plants
• Trans-boundary issue (especially in Europe and
  North America)

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Health Effects of Global Environmental Changes
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Possible adverse effects upon human health caused
by global environmental changes
Environmental change Manifestation Type (direct, indirect) and timinga (early, late) of adverse health effect Type (direct, indirect) and timinga (early, late) of adverse health effect Type (direct, indirect) and timinga (early, late) of adverse health effect Type (direct, indirect) and timinga (early, late) of adverse health effect
Environmental change Manifestation Direct, early Direct, late Indirect, early Indirect, late
Enhanced greenhouse effect Global warming and other climate change Heatwave-related illness and death Extension of vector-borne infections Altered viability of (edible) fish in warmed oceans
Natural disasters cyclones, floods, landslides, fires Food shortages due to impaired agriculture
Sea-level rise Increased risk of flash floods and surges Inundation ? social disorder, impaired sanitation, farmland loss Consequences of damage to foreshore facilities, roads, etc. Destruction of wetlands ? decline in fish stocks
Stratospheric ozone depletion Increased UV-B flux at Earths surface Sunburn, conjunctivitis Suppression of immune system ? increased risk of infection Skin cancer Ocular effects cataracts, pterygium Impaired growth of food crops and of marine microorganisms (base of aquatic food web)
Acid aerosols (from burning of sulphurous fossil fuels) Acid rain Effects on respiratory system (?) Aquatic damage (reduced fish) Impaired growth of crops Impaired forest growth ? reduced ecosystem productivity
A The designations early and late are
notional, and indicate relative timing. (Based
on McMichael, 1993.3)
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Possible adverse effects upon human health caused
by global environmental changes (cont.)
Environmental change Manifestation Type (direct, indirect) and timinga (early, late) of adverse health effect Type (direct, indirect) and timinga (early, late) of adverse health effect Type (direct, indirect) and timinga (early, late) of adverse health effect Type (direct, indirect) and timinga (early, late) of adverse health effect
Environmental change Manifestation Direct, early Direct, late Indirect, early Indirect, late
Land degradation intensive agriculture, overgrazing Erosion, sterility, nutrient loss, salinity, desertification Decline in agricultural productivity Rural sector depression ? migration to fringes of cities (see bottom row) Exposure to pesticides and fertilisers (may also cause algal blooms) Consequences of silting up of dams and rivers
Depletion of underground aquifers Lack of water for drinking and hygiene Decline in agricultural productivity
Loss of biodiversity Destruction of habitat Deforestation ? disruption of local culture Loss of potentially edible species Deforestation ? greenhouse enhancement
Loss of genetic diversity weakening of ecosystems Loss of medicinals, and other health-supporting materials Greater vulnerability of crops and livestock. Reduced vitality of ecosystems
Other effects of overpopulation (particularly in poor countries) Proliferation of crowded urban slums (due to migration and high fertility) Infections Malnutrition Homelessness Antisocial behaviours Social disorder Chronic toxic effects of environmental pollutants Consequences of overload of local ecosystems
A The designations early and late are
notional, and indicate relative timing. (Based
on McMichael, 1993.3)
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Regional/Local Air Pollutants

• Criteria (Common) Air Pollutants - (ambient air
  quality standards established)
• Regional
• Photochemical smog - Ozone (O3)
• Haze - Particulates (PM) Nitrogen Dioxide (NO2)
• Local
• Sulphur Dioxide (SO2)
• Carbon Monoxide (CO)
• Lead (Pb)
• Air Toxics - (often no standards)

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Air toxics or Hazardous Air Pollutants (HAPS) a
definition

• gaseous, aerosol or particulate pollutants
  (other than the six criteria pollutants)
• that are present in the air in low concentrations
  with characteristics such as toxicity or
  persistence so as to be a hazard to human, plant
  or animal life

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Air Toxics / HAPS

• Diverse range of toxic compounds
• Volatile Organic Compounds (VOCs)
• formaldehyde lung, eye, skin irritants
• benzene, 1,3-butadiene carcinogens
• Persistent organic pollutants (POPs)
• DDT, PCB, dioxins toxic, persistent,
  bioaccumulate
• Polycyclic Aromatic Hydrocarbons (PAHs)
• Benzoapyrene Incomplete combustion of organic
  matter lung cancer, immune system suppression,
  respiratory problems
• Toxic Metals (associated with PM or as gases)
• Arsenic, cadmium, lead, mercury, nickel,
  chromium persistent, bioaccumulate, toxic -
  kidney/liver damage, CNS disorders

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Air Toxics / HAPs

• Diverse range of point and diffuse sources
• point sources industries and other facilities
  emitting in a localised area
• diffuse sources mobile sources (eg road
  vehicles, boats), area based sources (eg wood
  burning, dry cleaning, paints, thinners)
• Indoor / in vehicle exposures
• Increasing regulatory / public concern
• Generally little or no exposure data
• US EPA - list of 189 HAPs (1990)

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List of priority hazardous air pollutants
(Commonwealth SOE 2001)
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NEPMS (standards) to be developed for 5 air
toxics in Australia

• benzene
• formaldehyde
• polycyclic aromatic hydrocarbons
• toluene
• xylenes

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Criteria for selection for inclusion

• Excluded air toxics from point sources
• Adequate ambient monitoring data exists
• Significant risk to human health
• Has highest mass emissions to the environment

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Review of air toxics and health studies in
Australia

• WA Department of Environmental Protection
• Found 10 studies
• 9 studies addressed air toxics and health
• 1 study measured personal exposure
• 1 study in the ambient setting, 9 in
  occupational/indoor settings
• Formaldehyde was the most researched air toxic

Source State of knowledge report Air toxics and
indoor air quality in Australia. (EA, 2001)
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Indoor air pollution

• Indoor air can be defined as any non-industrial
  indoor space where a person spends a period of an
  hour or more in any day.
• This can include the air space in the office,
  classroom, motor vehicle, shopping centre,
  hospital and home.

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Indoor air pollution

• The quality of indoor air is influenced by two
  major factors
• amount and quality of outdoor air getting in
  (ventilation rates, deposition and chemical
  decay)
• indoor sources of emissions of air pollutants

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Indoor air pollution

• In winter 80 - 90 of time indoors - mostly in
  own home
• A number of important indoor air pollutants
• Particles
• Environmental tobacco smoke (ETS)
• Oxides of nitrogen
• Formaldehyde
• Biological pollutants house dust mites, moulds,
  etc

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Particles in homes - no major sources
Source V Sheppeard, NSW Health
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Fine particle (PM10) levels by number of smokers
in house
Source V Sheppeard, NSW Health
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Fine particle (PM10) levels by main heating type
Source V Sheppeard, NSW Health
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Average levels of total suspended particles in
selected Sydney clubs hotels (NSW SOE 2001)
Source Cummins et al. 1990
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Average weekly nitrogen dioxide levels in homes
Source V Sheppeard, NSW Health
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Peak 1-hour average concentrations of nitrogen
dioxide, indoors outdoors, 1987-97 (NSW SOE
2000)
Source Ferrari 1997
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In car carbon monoxide levels
Source CARB 1998 V Sheppeard, NSW Health
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Other in-car exposures (VIC EPA - mean personal
concentrations while commuting to CBD (east
route) - pilot trial)
Source V Sheppeard, NSW Health
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Air toxics in other microenvironments
Source WA DEP V Sheppeard, NSW Health
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Burden of disease attributable to indoor smoke
from solid fuels( DALYs in each subregion)(The
World Health Report 2002)
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Ambient air pollution
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A historical perspective of air pollution

• In 1273, Englands King Edward I passed a law
  prohibiting the use of at least one type of coal
• In the early 1400's, Henry V formed a commission
  to oversee the use of coal in the city of London
• In 1661, Charles II ordered the scientist John
  Evelyn to survey the effects of the increasing
  air pollution over the city. Evelyn recognised
  the relationship between the dismal cloud over
  London and a number of fatal diseases but his
  warnings of the need for control were ignored

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A historical perspective of air pollution (cont)

• By the late 1800's industrialisation accompanied
  by the migration of people into cities increased
  the quantity and diversity of chemical pollutants
  entering the air
• In December 1873 weather conditions producing
  stagnant air and a temperature inversion ? thick
  cloud of pollutants covering London for several
  days ? about 1,150 deaths, making it one of the
  earliest air pollution disasters

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A historical perspective of air pollution (cont)

• Since 1873 at least 40 episodes of sudden
  buildups of air pollution have caused widespread
  casualties in the industrialised world

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A historical perspective of air pollution (cont)

• Several air pollution episodes occurred in
  London, England from December 1952 to 1962, with
  the most famous air pollution episode in December
  1952 being responsible for an estimated 4,000
  deaths.

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London smog and deaths (1)
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London smog and deaths (2)
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Early Control Measures

• Government regulation
• UK Clean Air Act (1956)
• US Clean Air Act (1963, 1970 amendement)
• Standards for 6 air pollutants (called criteria
  pollutants)
• Reviewed every 5 years
• Cost-benefit analysis
• Victorian Clean Air Act (1958), NSW Clean Air Act
  (1961)
• Standards to establish safe thresholds
• Control strategies to reduce/prevent exceedences

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Air Quality Standards

• USA
• 1970 amendment to the 1963 Clean Air Act
• National Ambient Air Quality Standards (NAAQS)
• UK
• Expert Panel on Air Quality Standards established
  in 1991
• Australia
• National standards in 1998

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Schedule 2 of the NEPM giving National
Environment Protection Standards for ambient air
quality (Commonwealth SOE 2001)
Pollutant Averaging period Maximum concentration (based on arithmetic means) Maximum allowable exceedencesA (days per year)
Carbon monoxide 8h 9.0 ppm 1
Nitrogen dioxide 1h 1y 0.12 ppm 0.03 ppm 10
Photochemical oxidant (as ozone) 1h 4h 0.10 ppm 0.08 ppm 11
Sulfur dioxide 1h 1d 1y 0.20 ppm 0.08 ppm 0.02 ppm 110
Lead (as TSPs) 1y 0.5 ?g/m3 0
Particles (as PM10) 1d 50 ?g/m3 5
A Goal to be achieved by 2008. Source NEPC (1998). A Goal to be achieved by 2008. Source NEPC (1998). A Goal to be achieved by 2008. Source NEPC (1998). A Goal to be achieved by 2008. Source NEPC (1998).
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Primary / secondary pollutants

• Primary pollutants
• Particles
• NOx
• SO2
• CO
• Secondary pollutant
• Ozone
• Particles (gaseous pollutants forming aerosols)

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Types of air pollution

• Summer episodes (photochemical episodes)
• Secondary pollutants O3, H2SO4, HNO3
• Ozone is the index pollutant
• White haze
• Winter episodes
• Particles, SO2
• Brown haze

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Air pollution concentration

• Complex interactions of many influences
• quantities of pollutants emitted, the spatial and
  temporal distributions of these emissions
• rates of pollutant transport, dispersion and
  diffusion in the atmosphere
• meteorological conditions such as temperature and
  sunlight intensity
• atmospheric chemical reactions
• topography of the region

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The role of the atmosphere in the air pollution
source sink relationship
DISPERSION Vertical and horizontal stability,
turbulence, wind TRANSFORMATION Chemical
reactions REMOVAL Settling, scavenging
adsorption, impaction
RECEPTOR RESPONSE Health effects, vegetation
damage, soiling, corrosion
EMISSIONS Rate, type, source configuration
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Sources of air pollution

• Mobile sources
• Motor vehicles, rail, shipping, aviation
• Industry sources
• Power stations, petroleum refining, chemical
  manufacturing
• Area based sources small point sources
• Service stations, combustion sources, lawn mowing

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• Sources of 1995 to 1996 emissions for Port
  Phillip Region, Vic.
• (Commonwealth SOE 2001)

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Source Commonwealth SOE 2001
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Sources of emissions and exposure to benzene in
the USA. (Commonwealth SOE 2001)
Source Data from Ott and Roberts (1998).
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Anthropogenic emission sources Sydney and
Greater MAQS region
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Pollutant emissions VKT of vehicle fleet, Sydney
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Contribution of wood burning to TSP, Sydney (NSW
SOE 2000)
Source Carnovale et al. 1997
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Why is air pollution an issue?

• Affects large numbers of people
• Involuntary exposure
• The health costs are enormous
• Also affects the health of flora and fauna
• Other health benefits from air pollution control
  ?road trauma, ?physical activity

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Burden of disease attributable to urban air
pollution( DALYs in each subregion)(The World
Health Report 2002)
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Total Annual Economic Costs of Motor Traffic Air
Pollution (AUDm) (Bureau of Transport and
Regional Economics 2003)
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Adverse health effects estimated to be avoided by
meeting the US EPAs 80 ppb 8-h average daily
maximum standard in New York City, NY. (Thurston
1997)
Deaths/yr
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Asthma Hospital Admissions/yr (0.01 of all
adverse impact cases)
Non-asthma Respiratory Hospital Admissions/yr
265
240
3,500 Respiratory ED Visits/yr
180,000 Asthma Attacks/yr (i.e., person-days
during which notably increased asthma symptoms,
e.g., requiring extra medication, are experienced)
930,000 Restricted Activity Days/yr (i.e.,
person-days on which activities are restricted
due to illness
2,000,000 Acute Respiratory Symptom
Days/yr (i.e., person-days during which
respiratory symptoms such as chest discomfort,
coughing, wheezing, doctor diagnosed flu, etc.
are experienced)
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Environmental human health effects of major air
pollutants (NSW SOE 2000)
Pollutant Effects environmental Effects human health
Ozone Damage to vegetation, reduced plant growth and crop yields, increased susceptibility to pests Long-term low-level exposure is of concern limited studies have been done on effects on Australian native vegetation Damage to fabrics, rubber and construction materials Irritation of eyes and air passages, decreased function, lung inflammation (potent oxidant), sensitivity of asthma patients to asthma triggers, possible increased susceptibility to infection
NO3 Effects on vegetation, damage to leaf surface, reduced plant growth Limited research has been done on Australian native vegetation Decreased lung function, lung inflammation, increased sensitivity of asthma patients to asthma triggers, increased susceptibility to respiratory infection
CO - Reduces the capacity of blood to carry oxygen can lead to decreased exercise capacity and aggravation of cardiovascular disease
Source NHMRC 1996 EPA 1997a
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Environmental human health effects of major air
pollutants (cont.)
Pollutant Effects environmental Effects human health
SO2 Plant damage and growth inhibition little known about effects on Australian native vegetation Acid deposition acidification of soils and lakes change the availability of minerals to plants Corrosion of construction materials Decreased lung function lung inflammation may provoke wheezing and exacerbate asthma
Fine particles Reduced visibility brown haze Increased rates of respiratory illnesses and symptoms, decreased lung function, excess mortality from heart and lung disease, exacerbation of symptoms in asthma patients
Lead Can accumulate in soil and food chain Altered neurobegavioural function in children, i.e. impaired intellectual development, increase human blood pressure and impair renal function
Air toxics Possible bio-accumulative effects (from accumulation in food chain) Long-term health effects, even at low concentrations Compounds may be carcinogenic, mutagenic, teratogenic, neurotoxic, toxic, or can cause reproductive dysfunction
Source NHMRC 1996 EPA 1997a
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Size distribution of particles in the
atmosphere (NSW SOE 2000)
Source EPA 1993 (data from ANSTO)
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PM10 Health effects

• Acute effects
• Decreased lung function
• Increased respiratory symptoms
• Hospitalisation/other health care visit
• Mortality
• Increased plasma viscosity,heart rate variability
• Chronic effects
• Increased mortality rates, reduced survival
  times, chronic cardiopulmonary disease, reduced
  lung function

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Stylized summary of acute exposure studies,
percent change in health end-point per 10 ?g/m3
change in PM10
84
Estimated percent changes in daily mortality
associated with a 10 ?g/m3 increase in PM10 (with
95 confidence intervals) for a number of cities
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Ozone - Acute Health Effects

• Decreases in lung function
• Increase in respiratory symptoms, asthma attacks
• Increase in restricted activity days
• Increase in hospital admissions especially
  respiratory admissions
• Increase in mortality

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The effect of ozone on pulmonary function (after
Kleinman et al., 1989)
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Effects of ozone on respiratory symptoms (after
Kleinman et al., 1989)
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Asthma camp associations between O3 levels and
both peak flow lung function change and asthma
exacerbations (as indicated by ?-agonist
medication use) (Thurston et al., 1997)
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Reported RR of respiratory hospital admission
associated with a 100 ppb increase in daily 1-h
max. O3 (Ito et al., 1999)
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Reported RR of mortality associated with a 100
ppb increase in 1-h max. O3 (Thurston et al.,
1999)
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Nitrogen dioxide Health effects

• Decreases in lung function
• Increase in respiratory symptoms
• Increase in hospital admissions asthma, COPD
• Increase in mortality conflicting results

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Potential human health effects of NO2
Health effect Mechanism
Increased intensity of respiratory infections Increased severity of respiratory infections Respiratory symptoms Reduced lung function Worsening of the clinical status of persons with asthma, chronic obstructive pulmonary disease or other chronic respiratory conditions Reduced efficacy of lung defences Reduced efficacy of lung defences Airways injury Airways and alveolar (?) injury Airways injury
Source Samet and Utell, 1990
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Adjusted prevalence of respiratory infections in
children of ten communities in Switzerland
according to the mean NO2 level (from
Braun-Fahrlander, 1997)
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Carbon monoxide health effects

• Angina and ischaemic heart disease
• Hospital admissions heart disease, asthma
• Mortality all cause and heart disease

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Relative risks of congestive heart failure
admission among Medicare patients as a function
of ambient pollutant levels
Pollutant and city Single-pollutant model Single-pollutant model Multipollutant model Multipollutant model
Pollutant and city Relative risk 95 Confidence interval Relative risk 95 Confidence interval
Carbon monoxide Carbon monoxide Carbon monoxide Carbon monoxide Carbon monoxide
Los Angeles Chicago Philadelphia New York Detroit Houston Milwaukee 1.36 1.29 1.17 1.10 1.24 1.11 1.29 1.25, 1.46 1.16, 1.44 1.05, 1.31 1.03, 1.18 1.11, 1.39 0.97, 1.26 1.07, 1.57 1.39 1.23 1.22 1.05 1.38 1.25 1.26 1.23, 1.56 1.07, 1.43 1.05, 1.41 0.97, 1.14 1.17, 1.63 1.05, 1.49 0.89, 1.77
Note The multipollutant model included all four
pollutants. All models included temperature,
month, day of week, and year. Values refer to
the relative risk associated with an increase of
10 ppm of carbon monoxide. From Morris et al.
(1995). Reproduced with permission of authors
and publisher.
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Sulphur dioxide Health effects

• Decrease lung function in those with asthma
• Increase in symptoms
• ED presentations
• Hospital admissions - respiratory
• Mortality all cause, respiratory and CVS

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APHEA studies

• For a 50 ug/m3 increase in 24 hour average SO2
• 3 increase in all cause mortality
• 4 increase in cardiovascular mortality
• 5 increase in respiratory mortality
• 2 increase in respiratory admissions (65 years)

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Types of studies

• Animal studies
• Human studies
• Experimental (chamber studies)
• Epidemiological (or observational)
• Cross-sectional
• Time series
• Case-control/ Case-crossover
• Cohort
• Randomised control trials

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Health outcome measures in studies of air
pollution
General
Overall mortality Morbidity index
Respiratory
Acute and chronic symptoms Acute infections Chronic respiratory diseases Degree of non-specific airways responsiveness Reduced level of lung function Increased rate of lung function decline Decreased rate of lung function growth Exacerbation of a chronic respiratory disease Hospitalization for a chronic respiratory disease Lung cancer Death secondary to a chronic respiratory disease
Neuropsychological
Reduced performance on neurobehavioural testing Neuropsychological syndrome Neuropsychological disease
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Some other health endpoints of interest

• Cardiovascular disease (AMI, heart failure)
• ECG changes
• Hospital admissions
• Mortality
• Perinatal outcomes
• Birth weight and gestational age
• Neonatal and infant mortality
• Cancer incidence lung cancer

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Determinants of exposure, dose and biologically
effective dose that underlie the development of
health effects (Modified from Jaakkola et al.,
1994)
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Indirect methods of assessing exposure
Source of information Type of information
Source strength Emission rate (mass per time), traffic density
Geographical information Distance of the place of residence from the source
Dispersion models Spatio-temporal concentration distributions from modelling of emission rates, meteorology, air chemistry, geography
Outdoor-indoor penetration Modelling from outdoor concentration, building an ventilation characteristics
Stationary monitoring Concentration over time modelling from concentration of pollutants in microenvironments
Questionnaires and interviews Source strength, distance from the source, time-activity
Personal monitoring Continuous or cumulated concentrations over time
Human samples Concentration of biomarkers of exposure in human tissues and hair
Toxicological models Concentration and dose of pollutants in target organs modelling from concentration, breathing rate, metabolism
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Some issues in air pollution

• Multi- pollutant exposure
• Low dose exposure
• Size and composition of particles
• Threshold effects
• Shape of the response function
• Time activity patterns
• Confounding by season and weather

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Uses of exposure response relationships

• Standard setting and risk assessment
• Cost benefit analyses
• Air pollution control programs

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Study involving modeled air pollution data
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A method for exposure assessment
Air Pollution
Population
Exposure
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Green Scenarios
TEST CASE- 25 reduction in motor vehicle usage -
public transport, car pooling, home office
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Selected references

• Department of Environment and Heritage. (2001)
  State of the Environment Australia 2001.Canberra,
  Australia. http//www.erin.gov.au/soe/atmosphere/i
  ndex.html (accessed October 2003)
• Department of Environment and Heritage. (2001)
  State of Knowledge Report Air toxics and indoor
  air quality in Australia. Canberra, Australia.
  ISBN 0 642 54739 4.
• Holgate ST, Samet JM, Koren HS, Maynard RL.
  (eds.) (1999) Air pollution and health. Academic
  Press. London.
• McMichael AJ. (1993) Planetary overload Global
  environmental change and the health of the human
  species. Cambridge University Press.
• New South Wales Environment Protection Authority.
  (2000) New South Wales State of the Environment
  2000. http//www.epa.nsw.gov.au/soe/soe2000/index.
  htm (accessed October 2003)
• New South Wales Environment Protection Authority.
  (1998) Action for air. The NSW Government's
  25-year air quality management plan. ISBN 0 7313
  0160 9. Chatswood, Australia, Environment
  Protection Authority.

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Thank You