Tiếp xúc cá nhân với Benzene của các nhóm dân lựa chọn, và tác động của giao thông trên hành khách tại thành phố Hồ Chí Minh đã được nghiên cứu. Nghiên cứu được thực hiện trong tháng Sáu, tháng Bảy và tháng 11 năm 2010. Số liệu sơ bộ cho thấy rằng trung bình, tiếp xúc cá nhân với Benzene cho những người không nghề nghiệp tại TP Hồ Chí Minh là ~ 18 mg m 3 và hầu hết các tiếp xúc là do đi lại . Tiếp xúc với benzene trong đi du lịch bằng xe buýt, taxi và xe gắn máy là, tương ứng, 2230, 2239 và 185240 mg m 3 . Điều khiển xe máyxe taxi, nhân viên làm đầy xăng và bán hàng rong bị phơi nhiễm cao trong ngày tại 116, 52, 32 mg m 3 , tương ứng. Đo thêm là cần thiết để đánh giá rủi ro tốt hơn và việc tìm kiếm các biện pháp hiệu quả để giảm tiếp xúc. Điểm nổi bật ► tiếp xúc cá nhân với Benzene tại TP Hồ Chí Minh là ~ 18 mg m 3 . ► phơi sáng trong thời gian đi lại là 2239 mg m 3 cho xe buýt và taxi chế độ. ► phơi sáng trong thời gian đi lại là 185240 mg m 3 cho chế độ xe gắn máy. Benzen tiếp xúc ► trong thời gian đi lại góp phần chính của tiếp xúc hàng ngày. Trình điều khiển ► xe máyxe taxi, nhân viên xăng đầy và người bán hàng rong là những người tiếp xúc cao.
Trang 1Personal exposure to benzene of selected population groups and
impact of commuting modes in Ho Chi Minh, Vietnam
Tran Thi Ngoc Lan a,* , Ngo Quang Liem a , Nguyen Thi Thanh Binh b
aUniversity of Science, Vietnam National University, 227 Nguyen Van Cu, HCMC, Viet Nam
bDivision of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
a r t i c l e i n f o
Article history:
Received 27 March 2012
Received in revised form
13 December 2012
Accepted 16 December 2012
Keywords:
Benzene
Personal exposure
Ho Chi Minh
Motorcycle exhaust
Commuter
a b s t r a c t Personal exposure to benzene of selected population groups, and impacts of traffic on commuters in
Ho Chi Minh City were investigated The study was carried out in June, July and November 2010 The preliminary data showed that on average, personal exposure to benzene for non-occupational people in Ho Chi Minh isw18mg/m3and most of the exposure is due to commuting Benzene expo-sure during travelling by bus, taxi and motorcycle is, respectively, 22e30, 22e39 and 185e240mg/m3 Motorcycleetaxi drivers, petrol filling employees and street vendors suffer high daily exposures at 116,
52, 32mg/m3, respectively Further measurements are needed for a better risk assessment andfinding effective measures to reduce exposure
Ó 2012 Elsevier Ltd All rights reserved
1 Introduction
Air pollution in urban areas is a serious problem of many
developing countries The rapid increase of the urban population
and low transport infrastructure in East Asia has resulted in
formation of megacities with dense motorcycle fleets like Kuala
Lumpur, Bangkok, Delhi, Hanoi and Ho Chi Minh City A
conse-quence of this is decline of air quality due to volatile organic
compounds (VOCs) and particulate matters discharged from
vehi-cles Many VOCs are considered toxic to humans, especially
benzene since it is known as a carcinogenic substance Benzene is
highly volatile, so most exposure is via inhalation The toxicity of
benzene is stated on the US Environmental Protection Agency (EPA)
website (2012b) Exposure to benzene increases the risk of
leukaemia in humans ( Bois et al., 1996 ; Crump, 1994 ; Rinsky et al.,
1987 ) Experimental animal studies, both in inhalation and oral
ingestion, showed evidence of increased risk of cancer in multiple
organ systems including the haematopoietic system, oral and nasal
cavities, liver, forestomach, lung, ovary, and mammary gland
( Cronkite et al., 1985 ; Snyder et al., 1980 , 1993 ) The risk of
leukaemia associated with lifetime exposure to benzene at 17, 1.7
and 0.17 m g/m3is 104, 105and 106, respectively ( World Health
Organization [WHO], 2000 ).
Benzene is carcinogenic; therefore, WHO and the US EPA do not recommend any safe level of exposure Benzene in urban areas mainly originates from vehicle exhaust and evaporation from fuel tanks Petrol- filling stations and garages contribute a significant amount of atmospheric benzene Other sources that signi ficantly increase indoor benzene levels are coal burning, tobacco smoking, off-gassing from building materials (paints, adhesives, etc.), use of benzene-containing consumer products and un flued oil and petrol heating Evaporation from fuel tanks of motorcycle might be important source of benzene in Vietnam since each family owns several motorcycles and a guest room is common parking place for motorcycles Human exposure to a pollutant is considered as the concentration of the pollutant in the air that one individual inhales, and differs from outdoor and indoor pollutant concentration Exposure depends on pollution level in the urban air, as well as in microenvironments that an individual is exposed to, and the duration of exposure Personal exposure to benzene of non-occupational non-smoking population was found to be higher than the outdoor ambient benzene level in Barcelona City metro-politan area and Catalan rural areas, Spain ( Gallego et al., 2008 ); in Rouen, Île de France (Paris area), Grenobleand and Strasbourg, France ( Gonzalez-Flesca et al., 2007 ); and in Copenhagen, Denmark ( Skov et al., 2001 ) The right method for the assessment of toxicity of benzene to humans is to relate benzene exposure to health effects.
Ho Chi Minh City, with a population of around 8.5 million, is one
of the most crowded cities in East Asia Public transportation consists of buses and taxis; however, the usage rate is low.
* Corresponding author
E-mail address:ttnlan@hcmus.edu.vn(T.T.N Lan)
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Environmental Pollution 175 (2013) 56e63
Trang 2Motorcycles are preferred for their flexibility The number of
motorcycles and automobiles in March 2008 were 3,444,868 and
346,355, respectively, increasing to 3.9 million and 386,000 by June
2009 On average, vehicle population increases about 10% per year.
Following this trend, the number of motorcycles at the end of 2011
was probably around 5 million Traf fic volume in the city is
extremely high Our traf fic survey at 29 major and 22 minor roads
on 24 November 2010 showed daily traf fic volume in a range of
1.7 104e4.7 105 vehicles/day with an average at
1.4 105vehicles/day Traf fic volume in rush hours (7 AMe8 AM
and 5 PM e6 PM) was 1.4 103e4.8 104, with average of
1.2 104 Motorcycles contributed 90% e91% of a traffic fleet On
average, the moving speed of a motorcycle is 20 km/h in non-rush
hours and 17 km/h in rush hours, road width is 18 m and buildings
are mainly three-storey Road area in rush hours was 10 e200 m2/
vehicle with a same median and geometric value of 29 m2/
vehicle (unpublished data) Traf fic jams are frequent A large
percentage of transportation means is made up of old technology.
EURO II standard takes power in Vietnam since July 2008, but it is
only applied for new imported vehicles.
According to Lan et al (2011) , a daily benzene concentration in
street urban air in Ho Chi Minh was 7 e117 m g/m3with a geometric
mean value of w45 m g/m3 A high concentration of benzene may
badly affect human health Up to date, there was not any published
data on exposure to pollutants in Vietnam This study aims to
investigate personal exposure to benzene of selected population
groups in Ho Chi Minh The study was conducted from the end of
2009 to the end of 2010.
2 Material and methods
2.1 Study population
Ten people in three groups were recruited Thefirst group consisted of two
housewives Exposure in this group is equivalent to indoor benzene levels Two
houses were chosen Thefirst house was located in a narrow residential lane located
w200 m away from a main street The other house is a small shop located on and
facing a main street An entrance to thefirst house was just opened and closed
few times in a day, while an entrance to the second house was opened from 8 AM
to 9 PM Windows on the second and thirdfloors of the two houses were opened
day around None of houses had an air conditioner and/or ventilator In Vietnam,
most houses and building facing streets are shops Commonly, shops are opened 12e
14 h per day The two houses are designated as off-road and roadside indoors,
respectively
Two students and a lecturer were in the second group for the study on exposure
during commuting and working in university Motorcycles are the most common
means of urban transportation in Vietnam Buses are mainly for university students
and temporary visitors Taxis and private cars are for high-income people One
student commuted by a city bus, another drove a motorcycle and the lecturer
commuted by a 4-seat taxi Departure and destination were two university
Campuses, but routes were different One-way mileage was about 25 km for the
motorcycle and taxi, 32 km for the bus following definite route One-way
commuting time was 1.5 h by bus, 1 h by taxi and 1 h 10 min by motorcycle in
the morning (6:30 AMe8 AM) The commuting time in the evening (after 6 PM) was
a 10e15 min shorter than in the morning About one third of the route was in
crowded narrow streets, and the other two thirds were in open-space roads From
w8 AM to w7:30 PM, the students and lecturer stayed in the university campus,
which is about 200 m away from a main road Benzene exposure in the second group
was designated as commuter/bus, commuter/taxi and commuter/motorcycle
Individuals in the third group were persons at high risk of exposure: a street
vendor, a motorcycleetaxi driver, a bus driver, a taxi driver and a petrol-filling
employee Working times of street vendors varied depending on cases The
vendor was working from 6 AM to 10 PM in the front of the roadside house This
selection enabled evaluation of influence of proximity to road to indoor benzene
levels Motorcycleetaxis are common in Vietnam Motorcycleetaxi drivers have no
definite working time, from a few to 14 h per day The motorcycleetaxi driver in the
study was on the streets for about 10 h/day In this time, he was driving for 7 h,
waiting in front of university about 2 h, and having lunch and dinner for more than
1 h The remaining time in the day, he was at home Commonly, street vendors and
motorcycleetaxi drivers are low-income people and most of them are temporary
residents of the city They usually live in houses located in narrow lanes in dense
In Ho Chi Minh City, departure of thefirst and last bus from a terminal is 5 AM and 8 PM The bus in the study was a diesel 47-seater, and was air-conditioned like most of buses in Ho Chi Minh The bus route was about 30 km Working time of the bus driver is from 5 AM to 10 PM with a break after each round Taxis in Ho Chi Minh run on petrol and operate throughout the day A working shift of a taxi driver is normally 12 h A 7-seat air-conditioned taxi was employed for a whole day for the study All taxis and<9-seat cars in Ho Chi Minh are air-conditioned Working time of the petrol-filling employee was 6 AM to 10 PM The petrol-filling employee wore
a facemask made of cotton-cloth layers This type of mask is very common in Vietnam for protection from sunlight, particles and pollutants, and Vietnamese citizens wear them when commuting by motorcycles The protection ability of facemasks from gas pollutants is not clear Normally, petrol-filling employees, taxi drivers and bus drivers work one week on and one week off
2.2 Sampling Passive sampling was applied for measurement of daily exposure of taxi and motorcycleetaxi drivers, while active sampling was used for investigation of hourly exposure in other cases Active sampling was performed according to the NIOSH
1501 method (NIOSH, 2003) Air was drawn into sample tubes (Sibata 80150-0541,
70 mmf6 mm/4 mm, 200 mg of activated carbon) at aflow of 100 ml/min in
55 min or 110 min using a programmable minipump (MPP
30, Sibata, Japan) The pump was calibrated using a bubbleflow meter A sample tube holder was attached
on a breast pocket Sampling was conducted throughout the day for the off-road house, 6 AMe10 PM for the roadside house, street vendor, commuters, bus driver and petrol-filling employee To simulate the air that petrol-filling employee inhaled, sampling tube was attached through a small hole into a PVC bottle (6 cm diameter and 10 cm height), the mouth of which was covered by the same facemask that the petrol-filling employee had Sample tubes after sampling were sealed with plastic caps Passive sampling was performed using Lanwatsu passive samplers (Lan and Binh, 2012) Passive samplers were attached on breast pockets Sampling duration was 24 h Sampling rates of the Lanwatsu passive sampler at 30C were 17.7, 16.2, 15.3, 15.1 and 14.4 ml/min, respectively, for benzene, toluene, ethylbenzene, p,m-xylenes and o-xylene Passive sampling was used in the second sampling campaign (November 2010) for taxi and motorcycleetaxi drivers, while active sampling was applied in thefirst sampling campaign (from June to July 2010) in other cases, Sampling was done in working days Totally, 65 samples were taken All samples were stored in a plastic bag sealed with a zippered laminar aluminium envelope and kept in an airtight box, cold-stored and brought to the laboratory
Sampling campaigns, climatic conditions obtained from Ho Chi Minh City meteorological station (VVTS) and mixing layer depth obtained from HYSPLIT Trajectory Model (NOAA) are given inTable 1andFig 1 Ho Chi Minh has tropical monsoon climate A year has distinct dry season (DecembereApril) and rainy season (MayeNovember) Temperature is stable all year round with a monthly average of
26Ce28C The difference between daytime and nighttime temperature is 8Ce
10C This difference is greater during the dry season compared with the rainy season Commonly, wind velocity in the evening is stronger than in the morning Surface thermal inversion is rather frequent in early morning in Ho Chi Minh The frequency of surface stable layers of several hundred metres at 7 AM is up to 30% for any month in a year Moreover, the thickness of surface stable layers during boreal winter time is double or triple that of the rainy season From March to May, the frequency of surface stable layers decreases while their elevation above the surface increases and reaches 1.2 km In addition, additional stable layers develop at 1.5e 3.5 km height above unstable layers during the dry season (Nodzu et al., 2006) The above conditions enable accumulation of pollutants on the surface in the early morning
2.3 Instrumental methods and materials 2.3.1 Chemicals and standards All chemicals (puriss, anhydrous, analytical standard grade; with a purity
>99.5%) were purchased from SigmaeAldrich Carbon disulfide was treated by adding 20 mL of concentrated sulphuric acid and 10 drops of concentrated nitric acid
to 1 L of the solvent and shaking for two days A CS2layer is then decanted off, dried with anhydrous sodium sulphate and distilled The treated CS2was checked for benzene by gas chromatography (GC) analyses Usually, one treatment is enough for complete benzene removal The bottle with benzene-free CS2was stored in a steel box containing activated charcoal at 5C to avoid recontamination
A calibration curved was constructed using six working standards containing benzene (0.110e3.52mg/ml), toluene (0.215e6.88mg/ml), ethylbenzene (0.0542e 1.72 mg/ml), p,m-xylenes (0.108e3.46mg/ml) and o-xylene (0.0550e1.76 mg/ml) and two internal standards (IS),fluorobenzene (3.20mg/ml) and chlorobenzene (3.46mg/ml) The working standard solutions were stored in darkness at5C 2.3.2 Analyses
Analysis was carried out within a week after sampling as it was described in our previous report (Lan and Binh, 2012) A six-point linear calibration curve showed correlation coefficients above 0.999 for all analytes The limit of detection was 1.42,
Trang 3p,m-xylenes and o-xylene One working standard was routinely injected after each
ten injections to correct a change in calibration curves The change was not more
than 2.6% for all analytes
Pollutant concentrations in the air were evaluated using Eq.(1)for both active
and passive sampling
C¼ðW WblankÞ 106
Where W and Wblank(mg) are the amounts of pollutant in sample and blank sample
by analyses, DE is desorption efficiency given by the producers for each lot of
charcoal and was 98% in this study, A is the sampling rate (ml/min), t is sampling
duration (hour)
Sampling rate of passive samplers was adjusted by using Eq.(2)
A1 ¼ A2
T1
303
1:5
(2) Where A1is a sampling rate at site temperature T1(K), A2is sampling rate at 30C
Two petrol types marketed in Vietnam, RON92 and RON95, were analysed
Petrol was diluted in benzene-free carbon disulphide containing IS and injected into
the gas chromatograph for quantification
2.4 Evaluation of daily benzene exposure
Daily exposure to benzene is evaluated using Eq.(3)
Daily exposure¼
P24
1 Hour Concentration Duration of exposure
Sampling in the case of the taxi driver was conducted for two 12-h working
shifts Actually, the taxi driver was exposed to the measured daily concentration for
only half a day, while the other half day he was exposed to indoor benzene levels in
his house Sampling was not conducted in the evening and at night for the
commuters, bus driver, taxi driver, street vendor and petrol-filling employee
Approximately, the indoor benzene concentration in the evening and at night in the off-road house was assigned to the in-house exposure of the above individuals This way of evaluation was reasonable since most of the houses in Ho Chi Minh are located on narrow residential lanes away from main roads, and the percentage of roadside houses and buildings is very small
The risk of leukaemia was roughly estimated using Eq.(4): here, the entire population groups were considered to be exposed to benzene levels found in this study for all their life
Risk¼104 Daily exposure
An average daily exposure to benzene for the non-occupational population in the city was approximately using Eq.(5), where a transportation usage rate was evaluated using Eq.(6)
Average exposure¼ Daily exposurecommuting mode i usage ratecommuting mode i
(5) Usage ratecommuting modei
¼ Number of persons in vehiclei traffic volume of vehiclei
P3Number of persons in vehiclei traffic volume of vehiclei
100 (6)
3 Results and discussion 3.1 Daily exposure to benzene in Ho Chi Minh City Daily exposure to benzene was given in Fig 2 The housewife in the off-road house was exposed to benzene levels of 2.7 m g/m3; while the one in the roadside house suffered 8.5-folds higher benzene exposure at 23 m g/m3 Exposure of the motorcycle etaxi driver and the petrol- filling employee was 116 and 52 m g/m3, and
is higher than roadside benzene levels of 45 m g/m3 The daily exposure for taxi and bus drivers was 21 and 15 m g/m3, lower than the exposure of the street vendor at 32 m g/m3 Exposure of the student commuting by a motorcycle was 19.6 m g/m3, about four folds of the exposure of the student commuting by bus (4.1 m g/m3) and of the lecturer commuting by a taxi (4.3 m g/m3).
Should the obtained values hold for the entire group population, the risk of leukaemia would be 1.2 105, 2.4 106, 2.5 106, 1.6 106, 1.4 105, 9.0 106, 1.2 105, 3.1 105, 1.9 105, respectively for motorcycle commuter, bus commuter, taxi commuter, indoor/off-road housewife, indoor/roadside housewife, bus driver, taxi driver, petrol- filling employee, and street vendor.
Up to now, there is not any published data on personal exposure
to pollutants and commuting behaviour in Ho Chi Minh City Ho Chi Minh is a big city in Vietnam with an area of 2095 km2 The distance from the northernmost point to the southernmost point is 102 km, and from the easternmost point to the westernmost point is 47 km Approximately, the average commuting time is considered to be
2 h/day/person In this situation, the students and the lecturer can
Table 1
Climatic conditions of the exposure campaigns
Rain Temperature (C) Relative humidity
(%)
Pressure (atm)
Wind speed (km/h)
Wind direction Mixed layer
depth (m) Range Average Range Average
Off-road June 14the15th 2010 No 23e34 28 47e100 80 0.9960 7 S, SW (daytime)
W, NW (night)
86e985 Roadsidea June 21st 2010 No 25e31 28 62e100 85 0.9943 9 E, SE, S 172e1296 Vendora
Bus driver June 25th 2010 No 26e30 30 46e94 75 0.9927 13 S, SW 139e1157 Petrol-filling employee June 30th 2010 No 24e34 29 41e100 80 0.9939 9 S, SW, W 138e1371 Commuter/bus, commuter/
motorcycle
July 6th 2010 No 24e33 28 51e100 79 0.9960 8 S, SE (daytime)
NE (night)
84e1115 Commuter/taxi July 8th 2010 No 23e34 28 49e100 78 0.9954 6 NE, NW 128e1750 Taxi and motorcycleetaxi
driver
Nov 24the25th 2010 No 23e31 27 51e100 80 0.9945 5 S (daytime)
NW (night)
76e900
aShort-time traffic jam was from 7 AM to 8 AM
T.T.N Lan et al / Environmental Pollution 175 (2013) 56e63 58
Trang 4be considered as representative of the three non-occupational
population groups working indoors and commuting by
motor-cycle, bus and car A percentage of the above population groups can
be roughly estimated from the traf fic volume of the above means of
transport The survey on the 24th November 2010 showed daily
traf fic volumes of motorcycles, 2e5-seat cars, 7e12-seat cars, 13e
29-seat passenger cars and >29-seat buses on 49 major and
minor roads in Ho Chi Minh were, respectively, 6,092,086, 122,292,
224,187, 33,516 and 30,335 (unpublished data) Approximately, the
number of 7-seat cars was about half of 7 e12-seat cars Normally,
12 e29-seat passenger cars are long-distance intercity buses;
therefore, only numbers of motorcycles, 2 e7-seat cars and
>29-seat buses are used for evaluation of the usage rate of commuting
modes On average, the in-vehicle number of people in one vehicle
is 1.3, 2 and 35 for a motorcycle, 2 e7-seat cars, and >29-seat buses.
Thus, the usage rate of motorcycle mode, car mode and bus mode is,
respectively, w87%, w1.3% and 11.7% Thus, an average exposure to
benzene for the non-occupational population that has to commute
would be 19.6 87% þ 4.3 1.3% þ 4.1 11.7% m g/m3¼ 18 m g/m3;
here the non-commuting population group was neglected since
this group is composed of elderly and under-1-year-old children.
3.2 Daily pro file of benzene exposure
It is important to know diurnal variation in benzene exposure
and sources of benzene This information is essential for effective
solutions for reducing exposure Measurement of diurnal variation
taken on a typical weekday showed that indoor exposure in the
off-road house was w4 m g/m3from 6 AM to 20 PM, four times higher
than 0.96 m g/m3at night Indoor exposure in the roadside house
was similar to outdoor exposure, although commonly the indoor
exposure was lower than the outdoor exposure, as the house had its
doors open Exposure was high in the morning and evening
peak-hours (7 AM e9 AM, 5 PMe7 PM) and low at midday ( Fig 3 (a)).
Should this hold for other days, we could assume that diurnal
variation of indoor exposure in the roadside house is the same as
diurnal variation of roadside benzene concentration found in our
previous study ( Lan et al., 2009 , 2010 ); accordingly, roadside
benzene concentration was well correlated with the number of
on-road motorcycles Indoor benzene levels at midday were higher
than outdoor benzene levels due to indoor stagnant conditions
depressing dispersion of pollutants A very high benzene
concen-tration in the early morning was due to the short-time traf fic jam in
the sampling day.
Fig 3 b gives the variation of exposure of the bus drive and
employee during the working day Exposure of the
petrol-employee varied a lot (30 ew130 m g/m3), and was high in the
Fig 2 Daily benzene exposure of different population groups in Ho Chi Minh
a
b
c
Fig 3 Hour variation in benzene exposure
Trang 5morning and at night, and low at midday This phenomenon is
dif ficult to explain since exposure of the petrol-employee depends
on many factors like traded amount of petrol, climatic conditions,
and working behaviour Benzene exposure of the bus driver was
15 m g/m3e35 m g/m3with an average of 22 m g/m3( Fig 3 b), and was
high in the morning and evening, and low at midday It is dif ficult to
explain variation of the exposure of the bus driver, since a bus is
a moving object Benzene levels inside a bus depends on many
factors like moving speed, number of stops, ventilation conditions,
outside benzene concentration, etc Low mixing layer depth or the
possible formation of a stable surface layer in the early morning and
at nighttime could be one of the many reasons for the observed
high exposure in morning and nighttime for the petrol- filling
employee and bus driver.
Fig 3 c reports the daily pro file of exposure to benzene of the
students and the lecturer Exposure during commuting by bus, taxi
and motorcycle was 22 e30 m g/m3, 22 e39 m g/m3and 185 e240 m g/
m3, respectively The high exposure of the motorcyclist is due to
direct exposure to highly polluted streams of exhaust gas from his
own motorcycle and other on-road vehicles in a dense traf fic fleet.
According to Lan et al (2010) , benzene concentration in exhaust gas
from 23 in-use motorcycles in Ho Chi Minh is in a range of 11 e
1078 mg/m3and largely depends on vehicle technology, moving
speed and accumulated mileage Benzene exposure should be
higher for lower technology and higher fleet density, depend largely
on climatic conditions Eye irritation and headaches are symptoms
that motorcyclist in big cities in Vietnam often suffer; therefore,
they normally wear protective facemasks On average, exposure to
benzene on the motorcycle was 7 e8 times of those in the bus and
taxi Benzene concentration was w3 m g/m3 in the university
campus, and w1 m g/m3at home during nighttime The contribution
of commuting in personal daily benzene exposure of university
students and staffs was almost 99% for motorcycles, and 60% e65%
in the bus and taxis In other words, commuting contributes
a main part of personal exposure to benzene This was reported by
Kuo et al (2000) and Horton et al (2006) for Taichung and Perth.
3.3 Comparison of benzene exposure in Ho Chi Minh and in the
world
Studies on benzene exposure were conducted over the world.
Examples are the EXPOLIS ( Hanninen et al., 2004 ) and PEOPLE
( Ballesta et al., 2006 , 2007 ) projects EXPOLIS is a population-based
study of urban adult personal exposures to multiple pollutants
conducted between 1996 and 1998 in Athens, Greece; Basel,
Switzerland; Grenoble, France; Helsinki, Finland; Milan, Italy; and
Prague, Czech Republic The PEOPLE (Population Exposure to Air
Pollutants in Europe) project is a study of outdoor, indoor and
human exposure to benzene The PEOPLE project involved six cities,
namely Brussels, Lisbon, Bucharest, Ljubljana, Madrid and Dublin A
similar project named UATMP ( US EPA website, 2012a ) was carried
out in the US A study on benzene exposure was also conducted in
Asia ( Liu et al., 2009 ; Navasumrit et al., 2005 ; Tunsaringkarn et al.,
2012 ).
Table 2 gives an overview of personal exposure to benzene
reported in the literature Ho Chi Minh City is in a group of
high-level exposure cities together with Athens and Bucharest In Ho
Chi Minh, only a small percentage of the population, living far
from roads and commuting by taxi or by bus, has almost the same
exposure as in Europe, the US and Asian developed countries,
while most of population is exposed to much higher benzene
levels Proximity to main roads and motorcycle commuting
signi ficantly increase benzene exposure Benzene exposure of the
petrol- filling employee during working time in this study was
30 e120 m g/m3, in the same order with the reported values of
17.5 m g/m3e51 m g/m3 for urban areas in Ioannina, Greece ( Karakitsios et al., 2007 ), 92.75 e121.67 ppb (290e390 m g/m3) in Bangkok, Thailand ( Navasumrit et al., 2005 ; Tunsaringkarn et al.,
2012 ) and 530 m g/m3 in Rome ( Carere et al., 1995 ) Daily benzene exposure of the bus driver was 15.7 m g/m3, almost half of 24.7 m g/m3found in Athens ( Chatzis et al., 2005 ).
Table 3 summarises mean in-vehicle benzene concentrations reported Motorcycle commuting is popular in Thailand, Malaysia, Vietnam, Pakistan and India On-motorcycle benzene levels found
in this study were in the same range of that reported for Taiwan In general, on-motorcycle benzene levels are higher than in-bus and in-car benzene levels, and in-car benzene levels were often found
to be higher than that of in-bus levels Except values obtained for Taipei, Taichung (Taiwan) and Sydney (Australia), benzene levels in buses and cars were from 5 m g/m3to 50 m g/m3.
3.4 Relationship between benzene and toluene
In urban areas, benzene is mainly airborne and generated by vehicular traf fic; therefore, toluene/benzene (T/B) ratio is often used to evaluate the contribution of sources to atmospheric benzene and toluene A good relationship between species indi-cates a single source A clearly distinguishable ratio indiindi-cates signi ficant contributions of different sources T/B values below 3 have been found to be characteristic of traf fic emissions worldwide ( Perry and Gee, 1995 ; Brocco et al., 1997 ; Heeb et al., 2000 ; Monod
et al., 2001 ; Chan et al., 2002 ; Hiesh et al., 2006 ; Kumar and Tyagi,
2006 ; Khoder, 2007 ; Truc and Oanh, 2007 ; Hoque et al., 2008 ;
Hoshi et al., 2008 ; Liu et al., 2009 ; Matysik et al., 2010 ) T/B values of 1.5 e4.3 are considered an indicator of traffic emissions, as reported
by Hoque et al (2008) and Liu et al (2009) For T/B values >4.3, solvent source impacts are probable A speci fic B/T ratio below 0.20
Table 2 Personal exposure to benzene (mg/m3) reported in literature
Average for population
Population commuting
by bus
Population commuting
by bus car Athens, Greece 13.1e24.6 Chatzis et al.,
2005
Helsinki, Finland 2.6ne4.7TSE Edwards et al.,
2001
Rouen, France 4.7 Gonzalez-Flesca
et al., 2007
Grenoble, France 6.4 Ile de France, France 5.3 Strasbourg, France 5.9 Florence, Italy 2.4s, 7w 2.3s, 6.6w Fondelli et al.,
2008
Perth (Australia) 1.76s, 1.98w Horton et al.,
2006
Copenhagen, Denmark
2001
Windsor, Ontario (Canada)
1.69s, 1.96w Stocco et al.,
2008
Oxford (England) 4.6 Lai et al., 2004
Brussels (Belgium) 5.1 4.5 5 Ballesta et al.,
2006
Lisbon (Portugal) 6.1 5 5.3 Bucharest (Hungary) 12.9 13.2 18.8 Ljubljana 5.5 4 5 Madrid 5.1 8.8 10.9 Dublin, Ireland 2.9 2.4 2.4 Daegu, Korea 2.6e8.1 Park and Jo,
2004
Madrid, Spain 6.5 10 Ballesta et al.,
2008
California, USA 5.1 Marshall et al.,
2006
s: spring, w: winter, n: non-smoking environment, TSE: tobacco smoking environment
T.T.N Lan et al / Environmental Pollution 175 (2013) 56e63 60
Trang 6has been proposed as an indicator of samples strongly affected by
industrial emissions in Dongguan, China ( Barletta et al., 2008 ),
while a ratio of 0.4 e1.0 has been used as an indicator of air
propelled by vehicular exhaust in Beijing ( Wang et al., 2012 ) T/
B > 4.3 was used to identify sources influenced by solvent use in
Windsor, Ontario, Canada ( Xu et al., 2010 ) A high T/B ratio (8.6) in
Taiwan suggested large additional sources of toluene from industry
( Hiesh et al., 2006 ) Monod et al (2001) reported an overview of
inter-species ratios between BTEX species in different
environ-ments in Asia, Europe and South America, accordingly T/B value
was 2.3 (R2¼ 0.91) for a traffic microenvironment.
The contents of benzene and toluene in RON92 and RON95
petrols were 1.81, 4.55 and 1.85 and 4.20 wt%, respectively Thus,
the T/B ratio in A92 and A95 gasoline were 2.5 and 2.3 Fig 4 shows
daily pro file of T/B ratio T/B was 1.9e2.3 for the motorcycle mode
and 3.1 e3.7 for the taxi mode, but was not put on Fig 4 due to
limited data T/B ratios for motorcycle, daytime outdoor air
(vendor) and indoor air, and bus microenvironment were similar to
that in petrol and in motorcycle exhaust ( Lan et al., 2009 ), implying
the same origin of benzene and toluene from gasoline vehicles The
higher T/B for indoor air and the street vendor in late evening and
nighttime can be explained by a change in fleet composition and increase of the contribution of off-gassing from construction materials due to decreases in traf fic volume Heavy trucks in Ho Chi Minh are allowed from 8 PM to 6 AM T/B was 3.1 e3.7 for taxi, and
5 e6 for the off-road house at nighttime, implying an additional source of toluene, possibly from fragrances T/B ratio for the petrol-filling employee was the low at 1.28e1.57 The low T/B ratio at the filling station is due to direct evaporation of petrol Light benzene evaporates more than toluene owing to higher vapour pressure and results in a lower T/B ratio in comparison with the ratio in petrol This phenomenon was observed by Correa et al (2012) , accordingly, the presence of lighter BTEX was more pronounced in the atmo-sphere of gas stations than in the gasoline vapour in equilibrium with the liquid petrol.
4 Conclusions Personal exposure to benzene was measured in Ho Chi Minh City The preliminary data showed that
(1) Benzene exposure was 22 e30 m g/m3for bus commuter, 22 e
39 m g/m3for taxi commuter, and 185 e240 m g/m3for motor-cycle commuter.
(2) Average personal exposure to benzene in Ho Chi Minh is around 18 m g/m3, about 40% of the benzene level in outdoor roadside air.
(3) Benzene exposure during commuting time contributes as the main part of daily exposure.
(4) Motorcycle etaxi drivers, petrol-filling employees and street vendors are people of high exposure to benzene.
Personal exposure to benzene is a changing parameter over time and depends on many factors such as vehicle technology, use rate of transportation modes, transportation behaviours, quality of fuels, condition of infrastructures, climatic conditions, etc Therefore, further measurements, which replication over time, are needed for
a be risk assessment.
Acknowledgement This research was supported by Vietnam National Foundation for Development of Science and Technology (NAFOSTED).
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