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Toxic effects of air pollution and it’s mitigation by urban
vegetation
Jo Cavanagh
Health effects of air pollution
• Respiratory effects –– Impaired lung function (developmental effects
in children) – Asthma incidence
– Chronic obstructive pulmonary disease (e.g. chronic bronchitis, emphysema)
• Cancer• Cardiovascular disease
Investigation of health effects
• Epidemiology– Study of population effects
• Toxicology– Study of mechanisms of effects
– Role of different physico-chemical properties of particulates
Sites of First Contact
LungTransition metals (eg Fe, Ni, V) Carbon coreOrganics
Lung lining
Blood
Epithelial cells
Unmodified
Alveolar macrophage
ModifiedAnti-oxidant rich
Cytokine induction
How do we do it??
Filter
PM10 collection Extraction
Soxhlet extraction GC-MS analysis
Analysis
What are we looking at?…..
• Carcinogenic potential (organic fraction)– Dioxin-like activity
– mutagenicity
• Inflammatory potential (primarily soluble (metals) fraction)– Inflammatory markers (IL-6, TNF-a)
– cytoxicity
Some preliminary results…….ambient air
samples
Auckland – dioxin-like activity (/m3)
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
1 2 3 4 5 6 7 8
Date
ER
OD
pg/
m3
0
5
10
15
20
25
30
Par
ticul
ate
conc
entr
atio
n (u
g/m
3)
EROD Particulate concentration
5/061/03 24/0428/0319/03 23/072/0730/05
Christchurch - dioxin-like activity (/ m3)
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
450.0
500.0
1 2 3 4 5 6 7 8 9 10 11
Date
ER
OD
act
ivity
pg
/m3
0
20
40
60
80
100
120
140
part
icul
ate
conc
entr
atio
n (u
g/m
3)
PM2.5 PM10 PM10 concentration PM2.5 concentration
7/065/03 28/044/0423/0317/03 16/0612/061/06 28/0623/06
Christchurch - inflammatory activity (water soluble fraction, / m3)
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
1 2 3 4 5 6 7 8 9 10 11
Date
TN
F-a
(pg/
m3)
0
20
40
60
80
100
120
140
Par
ticu
late
con
cent
rati
on (u
g/m
3)
TNF-a PM10 TNF-a PM2.5 PM10 PM2.5
7/065/03 28/044/0423/0317/03 16/0612/061/06 28/0623/06
Auckland - inflammatory activity (water soluble fraction, / m3)
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
1 2 3 4 5 6 7 8
Date
TN
F-a
(pg
/m3)
0
5
10
15
20
25
30
TNF-a
PM10
5/061/03 24/0428/0319/03 23/072/0730/05
Mitigation of air pollution
• Policy options– Warm homes initiatives
– Vehicles emissions testing– Vehicle maintenance
• Technological solutions– Improved fuel quality/alternative fuel types
– Engine efficiency/catalysts
• Urban vegetation
Significance of urban vegetation
• Estimated health benefit of £900,000 for Britain
• Saving of 140 lives by doubling the number of trees planted in the West Midlands, UK
• Removal of 234 t of particulates annually from Chicago’s air
• Preliminary estimates indicate1320 t PM10, 2740t NO2 removed by trees in Auckland
Processes for pollutant removal
Roadside vegetation
• Already has a number of purposes– Visual amenity
– Road run-off control/treatment– Visual aid to enhance road safety
• Few (no) studies have investigated the efficacy of roadside vegetation in enhancing air quality
Evidence for mitigation effects
• Dust accumulation on leaves of trees close to roadways
• Increased concentrations of contaminants in soil underneath roadside vegetation
• Increased concentrations of contaminants in leaves of trees close to roadways
Vegetation ‘structure’
• Hedge
Vegetation structure
• Hedge• Landscaped
Vegetation ‘structure’
• Hedge• Landscaped• Overhanging trees – median strip
• Overhanging trees – roadside
Factors influencing mitigation potential
• Dispersion of pollutants from roadways• Vegetation ‘structure’
– leaf surfaces– proximity to roadway
– height of vegetation
• Empirical data/modelling– ENVI-met (microscale climate model, UC)
Roadside distribution of particulates
Deposition from roadways
Riccarton bush (UC)
Summary
• Organic fraction of ambient air particulates demonstrate carcinogenic potential
• Water-soluble fraction of ambient air particulates demonstrate inflammatory potential
• Urban vegetation, including roadside vegetation, demonstrate potential for mitigation of particulate air pollution