Air Pollution and Health
• specific sections of the public most
affected by air pollution
• diseases of the cardiorespiratory system asthmatics and smokers far more likely to
be affected
Air Pollution and Health
Air Pollution and Health
• Pollutants act on surfaces of respiratory system
= chronic respiratory and cardiovascular disease
• alter O2 exchange in lungs, and transport in
blood
• Irritant pollutants = long term damage to eyes,
nose, throat and wet surfaces of body
• H2SO4 particles irritate mucous membranes and
cause bronchial constriction
Air Pollution and Health
• gaseous effects more acute than chronic (as
opposed to the particulate pollutants)
• SO2, O3 and NO2 are pulmonary irritants, may
cause congestion, oedema and haemorrhage
• NO, H2S and CO are asphyxiant gases
• organic gas pollutants e.g. acrolein (1-propenal)
as well as those gaseous pollutants mentioned
above produce eye irritation
Synergism
• Interaction between pollutants may be
additive, synergistic, or antagonistic
• Synergistic effects are those where the
sum of the effects of two or more
pollutants is less than the combined effect
i.e. 1 + 1 = 3
• The great majority of pollutant effects are
additive.
How are we affected?
three main routes by which pollutants enter
the body:
• absorption through the skin
• ingestion, and
• inhalation
Air Pollution and Health
Carbon Monoxide
• preferentially and irreversibly binds to
haemoglobin in blood forming
carboxyhaemoglobin
• reduces blood's capacity to carry O2 as CO has
a higher affinity (200X greater) for haemoglobin
than O2
• medical evidence suggests that continued
exposure to low levels of CO may cause
nervous disorders and be a factor in the cause
of heart disease
Carbon Monoxide
• CO in urban environments usually only a fraction
of those levels that cause asphyxiation
• low level effects = behavioural changes,
decreased time interval discrimination,
impairment of brightness discrimination,
increased reaction time to visual stimuli, and
lowered performance in driving simulations
• may be the cause of many motor vehicle
accidents in peak hour traffic of cities where
peak hour CO levels may rise above 50ppm
Carbon Monoxide
• For cigarette
smokers, CO
exposures far more
significant (an
average 3 – 8%
carboxyhaemoglobin
saturation) than those
experienced under
urban ambient
conditions
Concentration of CO (ppm)
Physiological Effect
10
Lowered awareness and
driving performance
50 - 100
Headaches and
drowsiness, changes in
driving performance and
increased reaction time
to visual stimulation
>250
Death
Sulfur Compounds
Sulfur Dioxide and Particulates
• Analysis of the effects of SO2 complicated by association
with particulate pollutants – direct effects of each
individual pollutant are difficult to separate.
• often produced by a common source, (combustion of
coal), hence high SO2 levels often associated with high
particulate matter levels - forming sulfate aerosols
• aerosols just the right size to be retained in the lungs so
cause maximum physiological damage
Sulfur Compounds
Sulfur Dioxide
• primary effect on respiratory tract, producing
irritation and difficulty breathing
• affects most strongly people with respiratory
problems
• children known to suffer increased frequency of
infection upon prolonged exposure to SO2
• long term effects of exposure not well
understood
Sulfur Compounds
Table 3.2 – Acute effects on humans of different atmospheric SO 2 levels
[SO2] in g/m3
Effect
500
Lowest level of human
sensation
Threshold of taste
Threshold of odour
Threshold for reversible
bronchial constriction
Immediate
throat
irritation
Immediate eye irritation
Immediate coughing
800
1400
4400
20000
30000
50000
Sulfur Compounds
Sulfur Dioxide
• London smog of 1952 averaged about 40005000g/m3
• Street levels in Wollongong in the late 1970’s
recorded values of 2250g/m3 – due to smelting
operations
• water solubility - SO2 almost entirely removed in
the mouth, throat, and nose through normal
breathing
• < 1% of inspired SO2 reaches lung tissue (alveoli)
Sulfur Compounds
Sulfur Dioxide
• principal effect of SO2 exposure is to alter the
mechanical function of the upper airway
• SO2 exposure at low levels (0.25 and
0.5ppm) produce acute bronchoconstriction
on inhalation
• likely that health effects of SO2 are due to
the highly irritant effects of sulfate aerosols,
such as sulfuric acid, which are produced
from SO2
Nitrogen Compounds
Nitrogen Oxides
• NO not health threat but is converted to NO2
• NO2 exposure at low levels (0.5ppm) destroy
cilia and obstruct respiration
• NO2 at 5ppm minor respiratory problems –
100ppm non-fatal inflammation – higher
levels fatal
Hydrocarbon Compounds
Hydrocarbons
• Most H/C’s relatively nontoxic at the ambient
levels found in normal atmospheres
• Form photochemical smog = very deleterious
to health - reduce visibility, have unpleasant
odours and cause skin and eye irritation at
higher levels - some carcinogenic, benzo[a]pyrene
• H/C air quality standards not based on health
effects, but an attempt to reduce
photochemical smog
Ozone and Photochemical Smog
Ozone
• Ozone = the most toxic pollutant regulated
under ambient air quality standards
• may cause significant physiological and
pathological changes in animals and humans
at conc’s within range measured in polluted
ambient environments
• The ambient air quality standard for O3 is
0.12ppm (235g/m3) averaged over 1 hour
Ozone and Photochemical Smog
Ozone
• O3 may cause significant lung function
changes even with exposures in the 0.100.40ppm range of for 1-2 hours
• Exposure to O3 levels above 0.12ppm, may
lead to a variety of symptoms including throat
dryness, chest tightness, coughing, pain,
shortness of breath, lassitude, malaise,
headache, and nausea
• may inhibit immune system's ability to defend
the body against infection
Particulate Matter
• exhibits toxic effects due to direct irritant
action of particles (such as H2SO4) and
substances readily adsorbed to the large
surface area of small particles
• concentration of adsorbed substances may
be considerably greater than in ambient
atmosphere
• adsorbed substances of particular concern
include SOx, PAH, and heavy metals e.g. Pb,
Cd, Zn and Hg
Particulate Matter
Retention
• health consequences depend on ability to
penetrate respiratory defence mechanisms
• remove inhaled particles in excess of 10m,
but particles smaller than can enter =
inhalable particles
• Particles < 2.5m = respirable, enter pulmonary
tissue
Particulate Matter
Retention
Particulate Matter
Retention
• deposition is slightly higher in smokers and
greatly increased in individuals with lung
disease
• retention varies greatly among the different
regions of the respiratory tract
• ciliated airways of the nose and upper
tracheobronchial zone, clearance in healthy
individuals is achieved <1 day
Particulate Matter
Retention
3
1
Total Suspended Particulate Level (ug/m )
Effect
1000
250 – 500
Increased mortality
Aggravation
of
bronchitis
Small reversible changes
in lung function of
children
• deeper in the
lungs the time
required for
clearance greatly
increases - 2
weeks to months
200
Particulate Matter
Lead
• Atmospheric lead normally a chronic cumulative
poison, mostly affecting the central nervous
system, blood & kidney
• at highest concentrations in particles of 0.2m or
less, which increases its access to animals by
allowing access to the deep lung tissue
• lead crosses the placenta, resulting in high lead
levels in the foetus, which may lead to mental
retardation - blood lead much higher in smokers
Particulate Matter
Asbestos
• inhalation of the fibres causes the lung disease
asbestosis –characterised by scarring of the lower
lungs and lowered breathing function
• Some forms of asbestos are responsible for
causing lung cancer and mesothelioma (cancer of
the lining of the body cavity)
• Asbestos fibres are chronic toxins with very long
latency periods - 1 fibre can kill eventually
Effects on Plants
• Plants often the first to show damage
associated with increased ambient levels of
air pollution
• effects of SO2, HCl and HF reported as early
as the middle of the 19th century
• most severe damage associated with high
levels of SO2 and heavy metal particulates
associated with mining and smelting
Effects on Plants
• visible effects involve changes in leaf
structure such as chlorophyll destruction
(chlorosis), tissue death (necrosis) and
pigment formation
• subtle effects include inhibition of growth and
lowered photosynthesis
Effects on Plants
Sulfur Dioxide
• harmful to certain plants at levels below 1ppm,
causing tissue damage and destruction of
chlorophyll
• enters plant tissues through stomates where it
comes into contact with the spongy mesophyll cells
of the leaf causing tissue collapse
• injury extends from the bottom to the top of the leaf
and is visible on both surfaces - alfalfa most
affected – injury at 1ppm for 1 hour
Effects on Plants
Sulfur Dioxide
Figure 3.4 – Tissue injury symptoms associated with exposure
to high levels of SO2
Effects on Plants
Ozone
• also enters the leaf through the stomates
• symptoms of acute injury are visible on the
upper leaf surface - younger plants more
sensitive and older plants more resistant
• most common O3-induced symptom patterns
observed on dicots are upper surface flecks
and some bronzing
Effects on Plants
Figure 3.5 – Leaf tissue injury associated with ozone exposure
Ozone
Effects on Plants
Figure 3.6 – Leaf tissue injury associated with ozone exposure
Ozone
Effects on Plants
Ozone
• sensitivity varies from species to species and from
variety to variety within species
• more toxic to plants than SO2. Symptoms may be
observed on sensitive plants from exposures of as
little as 0.10 - 0.30ppm for a few hours
• estimated to be the cause of over 90% of all plant
injury due to air pollution in North America
Effects on Plants
Peroxyacyl Nitrate (PAN)
• causes glazing/browning appearance on the lower
surface of the leaf
• PAN injury often appears as bands at the apex of
the youngest sensitive leaf, the middle of an
intermediate-aged leaf and the base of the oldest
sensitive leaf
• Young, rapidly developing leaves on young rapidly
growing plants are most sensitive to PAN
Effects on Plants
PAN
Effects on Plants
Fluoride
• substantial effects on growing plant tissue
• Injury from gaseous HF through the stomates
or from soluble particulate fluorides absorbed
through the leaves and/or roots
• fluorides enter veins and are transported to
leaf margins and/or the leaf tip, where they
accumulate - appears as tip burn
Effects on Plants
Fluoride
Effects on Plants
Particulates
• Direct effects such as those for cement kiln dust
include a variety of plant responses, such as
–
–
–
–
–
reduction in yield and growth without visible injury,
increase in disease incidence,
severe injury to leaf cells,
suppression of photosynthesis, and
death of trees
Effects on Buildings
• soiling building surfaces, clothing and other
articles
• Most important are effects on metals,
carbonate building stones, paints, textiles,
fabric dyes, rubber, leather, and paper
• Physical damage from abrasive effect of
wind-driven particulate matter - chemical
reactions when pollutants and materials
make direct contact