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Fine Atmospheric Particles:
Do we need to worry about
them??
Almost all combustion
leads to the formation of
fine particles
Mastery of Fire
400,000 years ago in Europe
100,000 years ago in Africa
M. N. Cohne, 1977
Ultimately we learned how
to use fire to clear land for
crops
In China 2000 years ago the Loess
Plateau was the cradle of ancient Chinese
civilization. Deforestation due to:
Firewood collection
Charcoal making
Creation of farm land
Brick making
resulted in a much drier and less
productive climate
• North American Indians used to burn
forested areas to promote the
growth of food ”sprouts”
• In Mexico deforestation often lead to
soil erosion and drier climates (800-
1400 before present-BP)
When fire was brought inside the
home very large smoke exposures
resulted:
These exposures are often much
higher in the developing world than
in the industrialized world
Women tend to spend more time
around unvented fires than men
In Nepal females and their very
young children receive much higher
exposures to indoor fires than males
(Kirk Smith, 1983)
Average cooking time is 2.8 hours
Prevalence of chronic bronchitis is
related to hours spent near the stove
Exposures are indoors as well as
outdoors Picture by Kirk Smith, India, early 1980s
After a few hours
Acute Respiratory Infections/6 month in
Rural Nepal Infants vs. time Near Stove
(M. R. Panday, 1984)
hours Mild Moderate Severe
near stove
0 to 0.9 1.7 0.3 0.05
1 to 1.9 2.1 0.5 0.08
2 to 3.9 2.3 0.6 0.7
4+ 1.8 1.0 2.8
Acute Respiratory Infections in Rural
Nepal Infants vs. time Near Stove
(M. R. Panday, 1984)
hours Mild Moderate Severe
near stove
0 to 0.9 1.7 0.3 0.05
1 to 1.9 2.1 0.5 0.08
2 to 3.9 2.3 0.6 0.7
4+ 1.8 1.0 2.8
Acute Respiratory Infections in Rural
Nepal Infants vs. time Near Stove
(M. R. Panday, 1984)
hours Mild Moderate Severe
near stove
0 to 0.9 1.7 0.3 0.05
1 to 1.9 2.1 0.5 0.08
2 to 3.9 2.3 0.6 0.7
4+ 1.8 1.0 2.8
Comparative Particulate
Concentrations in mg/m3
• U.S. Standard (PM2.5) 65
• Sydney (1996) ~25
• Traffic- Denmark 60
• London Smog (1952) 4,500
• Muese, Belgium 12,500
• Indian village 1,000
(Indoors ) 56,000
• Malaysia (1997, PM2.5) 800
• Thailand (1998, PM2.5) 300
Combustion forms a host of toxics that
are associated with soot particles
• Polynuclear aromatic hydrocarbons
(PAH)
• Chlorinated dioxins and furans
• Aldehydes and carbonyl compounds
Polynuclear Aromatic Hydrocarbons (PAH)
as a class of compounds are considered
potential carcinogens
Combustion Formation of PAH
Badger and Spotswood 1960
C
C C
C C C C
C C
C C
(I) (II) (III) (IV) C
Benzo a Pyrene
(VII) (VI) (V)
Combustion Formation of Dioxins from
Polychlorinated phenol
OH
C lx
OH .
C lx Flame
.O
Polychlorinated OH +
Phenol
C ly
+ OH O
O
C ly
C lx OH C lx O C ly
Chlorinated dibenzo dioxin
Shaub & Tsang, ES&T 1983.
Fresh wood soot in outdoor chambers (0.5
mm scale
Many of these compounds exist as a
free gas and on particles. This
influences:
• how they will be deposited on the
earth's surface
• the types of chemical reactions they
can undergo
• the route by which they enter the food
chain and are sorbed or deposited in
the lungs
Gas Particle Partitioning
toxic gas
particle
Langmuirian Adsorption (1918)
gas
surface
• = fraction of total sites occupied
• Rateon= kon (Pg) (1- );
• Rateoff= koff ;
• kon/koff= Keq
Langmuirian Isotherm
• K eq Cgas
1 K eq Cgas
• if Keq Cgas<< 1; = Keq Cgas
Junge (1977)
moles occupied sites / V
• K eq Pg
total# moles sites / V
= jcj /(Po + jcj)
= fraction in aerosol phase
Po= sat. vapor pressure of the pure
compound
j = conc. of aerosol surface (cm2/cm3)
cj =const, bBET, moles of sites/cm2, temp
cj=RTNse(Qi-Ql)/RT
A vapor pressure calculation for the liquid vapor for
anthracene
o Tb Tb
ln P 19 (1 ) 8.5 (ln )]
T T
Tb= 198 + SDTb ; C14H18 anthracene
anthracene has10, =CH- , carbons and each carbon = 26.73oK/carbon
It also has 4, =C< at 31.01OK/carbon
Tb = 198 + 267.3 + 124.04 = 589;
Published boiling point is = 613K
At 298K, lnPoL = -12.76; p = 2.87 x10-6atm = 0.0022 torr
Percent in the Aerosol Phase at
Different Aerosol Concentrations (25oC)
Phen Pyrene BaP
8x10-4 6x10-5 2x10-7
10 mg/m3 0.2 2 91
100 mg/m3 3.1 23 99
500 mg/m3 18 68 100
rural= 0.5 mm, high urban 0.35mm, Bangkok
=0.25mm
Yamasaki et al.(1982)
• Langmuirian adsorption
• [gas]
Ky
[part ] / TSP
• Assumes total # sites TSP (particle
conc)
• log Ky = -a(1/T)+ b
Yamasaki (1982)
• Collects Hi-vol filters+PUF
• Analyzes for PAHs
filter
BaA
log Ky
PUF
1/Tx1000
Yamasaki’s relationship
• This gives a log Ky = -a(1/T)+ b which is
compound specific
• Ideally from the regression values of a
and b, one can estimate the partitioning of
a given compound in any atmosphere at a
given temp. and TSP
[PAHgas ]
Ky
[PAHpart ] / TSP
Comparision of Yamasaki predicted vs
measured
Table IX-C-5-3. Average ratios of predicted Cgas/Cpart to measured Cgas/Cpart in the
Baltimore tunnel and at an urban sampling site in Chicago
Chicago Baltimore
Yamasaki et al Yamasaki et al
Phe 2.39a (1.76) 1.65 (0.59)
Ant 1.84b (0.99) 2.29 (1.06)
Fla 1.42 (0.88) 3.02 (1.55)
Py 1.77 (1.45) 1.30 (0.54)
BaA 0.26 (.14)
Chry 0.46 (0.41)
For this presentation extreme data points 21.19a and 45.2b and 38.0b were deleted from
Pankow analysis (Error! Bookmark not defined.); n= 10 samples in Chicago and in
Baltimore for most compounds, numbers in parentheses are standard deviations
Application of this theory
A number of years ago we conducted two
wood smoke experiments in our Teflon film
chambers to evaluate the stability of 9,10
anthraquinone.
The average chamber temperature for one
experiment was 20oC and the other was
38oC. A third experiment was conducted at
30oC, but only filters were analyzed. Data
from these experiments are given below.
UNC 25m 3Teflon Film Chambers
Three years later it became very important to
know the PUF (gas phase) and particle phase
distribution of anthraquinone at the 30oC
experiment.
It costs, however, 10,000 USD to re-run
experiments.
9,10-anthraquinone data in the gas
(PUF) and particle (filter) phases
Temp gas (PUF) particle (filter) TSP
ng/m3 ng/m3 mg/m3
38oC 228 105 0.512
20oC 38 381 0.366
30oC ? 440 0.832
So what do we do??
lnKy = -a(1/T)+ b
Temp is in Kelven
[PAHgas ]
Ky
[PAHpart ] / TSP
PAHGas PAHpart
XAD-2 (Gas) Filter TSP Ky 1/oK lnKy
ng/m3 ng/m3 mg/m3 (temp)
oC K
38 311 228 105 0.512 1.112 0.0032 0.106
20 293 38 381 0.366 0.037 0.0034 -3.310
30 303 ? 440 0.832 ? 0.0033
lnKy = -a(1/T)+ b
0.5
0.0
-0.5
(m 3/m g)
-1.0
ln Ky
-1.5
-2.0
y = -17295x + 55.716
-2.5
R2 = 1
-3.0
-3.5
0.0032 0.00325 0.0033 0.00335 0.0034 0.00345
1/oK
log Kp = -log Po(L) + const.
Kp= part/(gasxTSP)
slope = -1
log Ambient data of Pankow
and Bidleman
Kp
PAHs, alkanes
chlorinated
organics
log Po(L)
For liquid like particles
partitioning coefficient, Kp, is:
• Kip = 760 RT fomx10-6/{iPLtorr igMWavg}
log Kip = - log iPo(L) +C -log ig
• C= log [fom (7.501 RT)/ (106 Mwom)]
fom = fraction of particle organic mass
Mwom = avg. Mw of om in the particle
Calculating Activity Coefs, ig
• RT lnigom= iV[(omdd - idd)2 +ib(omdp - idp)2
+ ib(omdh - idh)2]
+ RT [ln(iV/Vom) +1- iV/Vom]
• Vom is the molar volume of the mix
ds are solubility parameters
dd = S Fd,j / iV
OH
by
Partitioning & uptakeCH the lungs
CH(CH3)2
CH (CH ) 3 2 18 3
eicosane
2-isopropylphenol
• Nicotine CH3(CH2)14COOH
(Pankow’s group)
palmitic acid
benz[a]anthracene
Cl Cl
N CH3
PCBs
N
Nicotine
Uptake by the lungs (Nicotine)
• Under normal circumstances Nicotine
can exist as a neutral “free base” or as
a protonated mono or di-acid and will
appear predominately in the particle
phase.
• Typically cigarette smoke has pH
values 3 and much of the nicotine
exists in the acidified form on particles.
Nicotine
• The acidified form can not partition
between the gas and particle phase.
• If ammonia is added to the tobacco
smoke, “as a flavor enhancement”, the
pH increases moving the equilibrium on
the particles from the mono-acid to the
neutral form.
Impact and “advantages” of ammonia
“flavor enhancement” on partitioning
• In the neutral form nicotine can
partition to the gas phase.
• neutral nicotine can then be readily
absorbed by the wet surface of the
inner lung (Pankow’s group)
• loss of nicotine to the lungs “pulls”
more nicotine off the particles
What are aerosols?
• Aerosols are simply airborne particles
• They can be solids or liquids or both
• They can be generated from some of
the following sources:
What are aerosols?
• Aerosols are simply airborne particles
• They can be solids or liquids or both
• They can be generated from some of
the following sources:
1. combustion emissions
2. atmospheric reactions
3. re-entrainment
What are some of the terms
used to describe aerosols?
What are some of the terms
used to describe aerosols?
• Diameters are usually used to describe
aerosol sizes, but aerosols have
different shapes.
Often particles are sized by
their aerodynamic diameter
• The aerodynamic diameter of a particle is
defined as the diameter of an equivalent
spherical particle (of unit density)
which has the same settling velocity.
• It is possible to calculate the settling
velocity of a spherical particle with a
density =1
• Density = mass/volume
DensityH20 = 1gram/cm3= 1
• Terminal Settling velocity (Vs ) is the
rate that a particle falls due to gravity
Vs g
1 d2
p
18 m
Often when we measure particles
they cover a large range of sizes
The normal distribution
1 x av gx2
fre q x ) 1 / 2 e xp
(
2 2 2
x avgx 2 1/ 2
n
A Log normal distribution is often
applied to the size data by plotting
the logs of the particles size vs
frequency
The log of the
geometric mean is
log diameter
10-31-05 number
4000
9:15"
3000
10:04
#/cc
2000 10:37
11:18
1000
11:56
0
10 100 1000
nm
The log normal distribution
Aerodynamic diameters of
some particles
• tobacco smoke 0.25 mm
• ammonium chloride 0.1
• flour dust 15- 20
• fogs 1- 5
• pollens 15- 70
• talc 10
• photochemical aerosols 0.01-1
Aerosol exposures
Indoors
Outdoors
Cars
Work place
Aerosol exposures
Indoors (90% of our time)
– ventilation systems
– mechanically re-entrain
particles (dust mites)
– cooking
Indoor activities generate
particles
Activities that generate aerosols in
Kamens home
Cooking stir-fried
vegetables: Kamens
house, 1987, EAA data
Vacuuming in Kamens House
Kamens house at night
How do particle sizes distribute
in the atmosphere??
How do particle sizes distribute
in the atmosphere??
.3-.8 um
4-10 um
Particle samplers often collect
particles smaller than a given size
• PM10 is defined as particles with
diameters < 10 mm.
• It is measured in units of mg/m3 ,
typically by pulling air through filters.
• PM2.5 is defined as particles with
diameters < 2.5 mm
• The choice of measuring at exactly
PM10 or PM2.5 is somewhat arbitrary
• Some people argue for a PM1.0
• Until recently only PM10 has been
measured in Thailand
Why is this important???
Why is this important???
Naso-oro-
pharyngo-
Tracheo-
bronchial
Alveolar
Where do particles deposit??
Large particles deposit in the
Naso-oro-pharyngo- region
Very fine particles (< 0.01 mm)
deposit in the Tracheo-bronchial
About 15-20% of the particles
between 0.1 and 1 mm deposit in
the Alveolar region
How do particles distribute
in the atmosphere??
.3-.8 um
4-10 um
Aerodynamic diameters of
some particles
• tobacco smoke 0.25 mm
• ammonium chloride 0.1
• flour dust 15- 20
• fogs 1- 5
• pollens 15- 70
• talc 10
• photochemical aerosols 0.01-1
• Car exhaust 0.1- 0.3
Urban Particle Exposure and its
Association with Mortality and
Morbidity
Killer Particles
Recent Particle Health Studies
• Dockery et al., N. Eng .J. Med, vol 329,
p1753, 1993)
• looked at 6 American cities with different
annual PM2.5 concentrations
• From 1974 to 1990, they followed 8111 males
and females.
• Subjects were 25-74 years old
Mortality rates were estimated
from:
• Survival times (date of death minus the start
date for that person in the study)
• Raw mortality rates are computed, for each
city, which are the number of
deaths/year/100,000 people
• These were adjusted for smoking, education,
body mass index, and other risk factors
Mortality vs. particle exposure
1.3
1.2
mortality
ratio 1.1
1.0
10 20 30 40
2.5 mm particle conc. in mg/m3
• On a mass basis urban fine particles may
be more toxic than cigarette smoke
Another Study by (Pope et al., Am
J. Crit. Care Med., vol 151, p669,
1995)
• looked at 151 cities with different
annual PM2.5 concentrations in 1980
• 552,138 mostly white adults
1000
y = 6.9492x + 695.51
950 2
R = 0.426
900
850
800
750
700
650
600
0 10 20 30 40
2.5 mm particle conc. in mg/m3
• Used a Cox multiple regression analysis
proportional hazards model
• Fleming, T.R. and D.P Harrington
Counting Processes and Survival
Analysis. John Wiley, New York,1991
• SAS Technical Report P-217; SAS/STAT
Software: The PHREG Procedure.
Version 6; SAS Institute, Cary NC,USA
Using their model they could look
at the risks associated with:
• age
• sex
• race
• cigarette smoking
• passive smoke exposure
• body mass
• alcohol intake
• education
• occupational exposure
Adjusted Mortality Risk Ratios for
exposure to 24.5 mg/m3 fine particles
Smokers
– women 1.16
– men 1.18
NEVER SMOKED
– women 1.22
– men 1.14
The Pope et al. study concludes that:
• Risks for increased pollution exposure
were the same for smokers and non
smokers
• The association between pollution and
mortality was not very sensitive to:
occupation, education, body mass,
alcohol, and temperature
• occupational differences between men
and women did not matter
There are other studies of this type
• Typically they find the strongest
relationship with fine particles and
sulfate aerosols
• There is usually an association with all
particles < 10 or 15 mm, but it is not as
strong as with fine particles
• Less of a relationship with aerosol
acidity and almost none for O3 CO,
NOx
The latest interpretations do
not find the strong relationship
that was observed back in
1993, but still report a
significant particle exposure
and mortality relationship (this
is what is in your book
chapter, Figure 2-21)
In A Particle Study
in Bangkok, 1998
• health effects were associated with
airborne particles
• They measured PM10
• Particle concentrations in Bangkok
tend to be higher than in other cities
around the world
• The results suggest that at current
PM10 concentrations in Bangkok, there
are between 1,000 and 2,000 premature
deaths each year
• These deaths are attributable to short-
term exposures to outdoor airborne
particulate matter
• This represents about 5% to 10% of all
recorded deaths in Bangkok
• Hospital admissions for
respiratory and cardiovascular
illness are higher when PM10
concentrations are higher
• For highly exposed adults, during
the winter months, who do not
spend much time in air-
conditioned environments,
• outdoor PM10 was associated with
twice the incidence of acute
respiratory symptoms than was
predicted when there is no
pollution
• For adults who spend substantial
time in air-conditioned
environments, the average outdoor
particulate matter during the winter
months still increased their
symptoms by about 20%
These types of studies
• suggest a 1-2% increase in the mortality rate
for every 10 ug/m3 of fine particulate matter
(Schwartz et al, 1996)
• Contributed to the US EPA setting a PM2.5
ambient particle standard at 65 mg/m3 for
24 hours, not to exceed the 3rd highest
value in 3 years; sampling ~1 time per
week
Why is there a linear mortality rate
response to particulate matter
and what is the mechanism??
Samet et al. at UNC have recently
exposed human airway epithelial
cells to residual oil fly ash (ROFA)
particles
• cells secreted prostaglandins
• Prostaglandins are a class of potent
inflammatory mediators which play a
role in inflammatory, immune and
functional responses in the lung
Human volunteers had inert Fe2O3 particles
introduced into their lungs (Lay et al, 1995)
• Produced a subclinical inflammatory
response in the first 24-48 hours
• Influx of macrophages and neutrophils
onto the alveolar spaces as assessed by
bronchoalveolar lavage
• Protein releases suggests alveolar
epithelial damage
• Leakage of plasma protein and fluids in
to alveolar space alters gas exchange of
injured tissue
• This is not a problem for a healthy
person
• people with compromised cardiac or
pulmonary systems, however, may not
be able to compensate or tolerate even
mild exposures
• ChiangMai, Thailand
• Do we see the same kinds of
particle health responses in
northern Thai Populations??
• Currently, there are only a
few studies which relate
PM2.5 on a daily basis to
mortality and morbidity
• Chiang Mai was selected because
it has high average fine particle
concentrations
• The concentrations change
significantly with the seasons
• We wanted to see if mortality
would track the changes in particle
concentrations
PM10 concentrations change
with the seasons
140
120
100
PM10 (ug/m3)
80
60
40
20
0
Jan Mar May Jul Sep Nov
• The population of the city of
Chiang Mai is ~170,000 people
• If the average death rate is 750 people
per 100,000 people per year
• This will give on average 3 or 4 deaths
per day
IN 1998, The US EPA provided
CMU with particle samplers
• 8 saturation samplers with batteries;
• more than 1000 Teflon filters; these
can be used to obtain particle mass
• Flow calibration gear
• 7- small samplers for personal
monitoring
• Saturation sampler for PM2.5 or PM10
PM2.5 or PM10 inlet
47mm filter holder
pump
rotameter
on/off digital lunch
timer
Battery
18cm
• It can be hung or strapped to a post
pump
Battery
~18cm
So how do these samplers
work??
Sizing particles with impactors
Impactors bring aerosols through a jet
The particles and air speed up as they
go through the small orifice
Sizing particles with impactors
Impactors bring aerosols through a jet
disk
• A disk or plate is place down stream of
the jet
Sizing particles with impactors
Impactors bring aerosols through a jet
• The disk has grease or oil on the
surface
Sizing particles with impactors
• Depending on the speed through the
jet, large particles will hit the disk,
while small particles follow the air
around the disk
Sizing particles with impactors
Filter
• A filter is placed under the disk to
collect particles that do not hit the
disk
• From this you can see the flow rate is very
important.
• The EPA samplers must flow at 5 liters/min
• If we calibrate them in the lab at one
temperature we must estimate the
temperature, and pressure when we sample
outside
• From this you can see the flow rate is very
important.
• The EPA samplers must flow at 5 liters/min
• When we calibrated them in the lab at one
temperature, we had to estimate the
temperature and pressure when we sampled
outside
Pcal Tamb mstd
kamb Qstd I amb bstd
PambTcal kamb
• We changed filters and the battery once
per day, 7 days / week
• Filters are weighed on a 5 or 6 place
balance and stored in plastic petri
dishes
Located samplers
• residential area in the city- PM2.5
• 5th roof top- urban sample not
influenced by different sources
- PM2.5 & PM10
• high population density area (down
town market?)- PM2.5
• relatively clean air- PM2.5
How do the samplers compare
to each other when they are
sampling in the same location
??
We located 6 samplers on the 2nd floor
outside porch of Nui’s house and
sampled for 24 hours on March 1, 1998
We located 6 samplers on 2nd floor
outside porch of Nui’s house and
sampled for 24 hours on March 1, 1998
120
100
ug/m3
80
60
40
20
0
6 2 4 1 5 3
Pump ID#
average 121 ug/m3
2 x % std 8.4%
Four different sampling locations
were selected for monitoring PM2.5
• Down town area (Nui’s house)
• Residential area (Dr. Usanee’s
house)
• General city exposure (outside 5th
floor of medical school)
• Background (2nd floor -Galae )
ChiangMai
PM2.5 concentrations
300
250
200
ug/m3
150
100
50
0
12-Ma 28-Ma 13-Ap 29-Ap 05/15
20-Ma 05-Ap 21-Ap 05/07
Nui
PM2.5 concentrations
300
250
200
ug/m3
150
100
50
0
12-Ma 28-Ma 13-Ap 29-Ap 05/15
20-Ma 05-Ap 21-Ap 05/07
PM2.5 standard Nui
PM2.5 concentrations
300
250
200
ug/m3
150
100
50
0
12-Ma 26-Ma 09-Ap 23-Ap 05/07
19-Ma 02-Ap 16-Ap 30-Ap 05/14
Usanee
PM2.5 concentrations
300
250
200
ug/m3
150
100
50
0
12-Ma 28-Ma 13-Ap 29-Ap 05/15
20-Ma 05-Ap 21-Ap 05/07
Usanee PM2.5 standard
PM2.5 concentrations
250
200
150
ug/m3
100
50
0
12-Ma 26-Ma 09-Ap 23-Ap 05/07
19-Ma 02-Ap 16-Ap 30-Ap 05/14
Galae
PM2.5 concentrations
250
200
150
ug/m3
100
50
0
12-Ma 26-Ma 09-Ap 23-Ap 05/07
19-Ma 02-Ap 16-Ap 30-Ap 05/14
PM2.5 Standard Galae
How do the samplers at the
different sampling locations
compare ??
ChiangMai
PM2.5 concentrations
350
300
250
ug/m3
200
150
100
50
0
12-Ma 26-Ma 09-Ap 23-Ap 05/07
19-Ma 02-Ap 16-Ap 30-Ap 05/14
Usanee Kalae sndok2.5 Nui
When we sampled for more than one
year
winter
winter
Summer
Summer
Chiang Mai Forest Fire Control Unit’s
show the following number of fires
1998 1999
Dec 0 10
Jan 63 361
Feb 647 1699
Mar 1214 949
Apr 241 943
May 5 28
Jun-Nov 0 0
Winter Summer
Mixing 900 1400
height in
meters
(afternoon)
Avg Wind 3.3 5.2
speed
Km/hr
Temp (oC) 30/17 35/25
(avg
high/low)
160 PM 2.5 level mg/m3 300
His + of TA100/plate
140 250
120 Mutagenicity vs.
P M 2 . 5 le v e l
100 200
PM 2.5
80 150
60 100
40
20 50
0 0
M a r - 8 p r - 9 8 a y - 9 8 Jun
Mar998 A Apr M May Ju n - 9 8 Jul
Ju l- 9 8 Sep
AAug8 S e p - 9 8
ug-9
PM 2.5 levels and air-borne mutagenicity in Chiang Mai ambient
m onth
air at different monitoring sites in the same month. Bar graph =
PM 2.5 level at
sit e 1 sit e 2 sit e 3 sit e 4
T A100+ S9(# 1) = site
=Tsite0 1,+ S 9 ( # 4 = siteT2,1 0 0 + S 9 ( # 3 ) 3, T A 1 0 = +site (4. 2 )
A1 0 ) A 0 S9 #
Line = mutagenicity at
= site 1, = site 2, = site 3, = site 4,
spontaneous revertants have been substracted already.
ChiangMai
If the downtown site, for example,
“experienced” a slightly higher
exposure to diesel exhaust which, is
much more mutagenic than wood
smoke, the PM levels would appear
similar, but the mutagenicity would be
influenced by the diesel particles and
appear higher.
A high prevalence of asthma in children living in
Chiang Mai has been reported.
At the present time, however, it is difficult without
further study to know if open burning is
exacerbating the asthma problem in Chiang Mai.
It would seem prudent, given the high fine particle
concentrations, to curtail open burning as much as
possible. Future studies should also attempt to
identify compounds in Chiang Mai air that are
potentially toxic to human health so that these may
be used as bench marks for future control
strategies.
Recommendations?
2 stroke motor cycles account for half of
the motor vehicles and can emit more than
10 times the amount that gasoline cars do.
We need to go to 4 stroke engines
Replace small diesel pick-up trucks
gasoline engine pick-up trucks-
maintenance off all vehicles
Control open burning!!
