Indoor environmental parameters are related to
house typology in the South of Vietnam
Thanh Ngoc Tran (  dr.tranngocthanh@pnt.edu.vn )
Pham Ngoc Thach University of Medicine
Diem K. T. Nguyen
Industrial University of Ho Chi Minh City
Thuy T. T. Tran
Industrial University of Ho Chi Minh City
Jean-Marie Hauglustaine
EnergySuD - University of Liège (ULg)
Olivier Michel
CHU Brugmann - Université Libre de Bruxelles (ULB)
Catherine BOULAND
Université Libre de Bruxelles (ULB)
Research Article
Keywords: Indoor pollutants, carbon monoxide, carbon dioxide, PM2.5, VOC, endotoxin.
Posted Date: March 13th, 2023
DOI: https://doi.org/10.21203/rs.3.rs-2559340/v1
License:   This work is licensed under a Creative Commons Attribution 4.0 International License.
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Abstract
Background: Several indoor pollutants such as carbon monoxide, carbon dioxide, volatile organic
compounds, particulate matter with aerodynamic diameter under 2.5μm (PM2.5) and endotoxin in house
dust contribute to increasing the risk of chronic respiratory diseases. The types of dwellings and housing
ventilation can affect indoor pollutant concentrations.
Methods: Our study was carried out on 100 houses to define indoor air (IA) characteristics of 5 typical
house types (apartment, rental, rural, slum and tube houses) in Ho Chi Minh City.
Results: The measured mean concentrations reached respectively 2.37ppm for carbon monoxide,
485.10ppm (441.60-520.50) for carbon dioxide, 23.20µg/m3 for PM2.5, 70.40ppb for VOC, 300C for
temperature, 60.5% for relative humidity, 107.80EU/mg for living room endotoxin, 124.50EU/mg for
bedroom endotoxin and 149.10EU/mg for kitchen endotoxin. Most parameters were differently
distributed among the five studied house types (p<0.05, ANOVA one-way), except for PM2.5, VOC, and
relative humidity.
Conclusion: Two house types (rental house and slum house) presented higher levels of most parameters,
while the rural house presented higher PM2.5 and endotoxin levels than all the other house types. The
apartment showed lower concentrations of all parameters than the other house types. In a later phase,
the IA characteristics will be confronted with the prevalence of chronic respiratory diseases.
1. Background
Prevention of Chronic Obstructive Pulmonary Disease (COPD) is considered a worldwide priority due to its
morbidity, mortality and heavy economic burden (1–4). Cumulative smoking is the most important risk
factor to develop COPD. Though about half of all COPD cases, worldwide, are due to non-tobacco-related
risk factors. Recently reviewed by IA Yang et al (5), risk factors include air pollution, occupational
exposures, poorly controlled asthma, environmental tobacco smoke, infectious diseases, and low
socioeconomic status. A body of evidence suggests that indoor pollution (IP) plays a major role (1, 6–
10). In low-middle income countries (LMIC), women are particularly affected by the disease because they
stay at home for long periods. In Vietnam, the prevalence of COPD is 8.1% (and 11.1% in urban Vietnam)
(5). The prevalence is 5,3% among women, most of them being non-smokers but exposed to indoor air
pollution (11–13).
Several indoor pollutants (carbon monoxide (CO), carbon dioxide (CO2), volatile organic compounds
(VOC), particulate matter with aerodynamic diameter under 2.5µm (PM2.5) and endotoxin in house dust)
contribute to increasing the risk of COPD (1, 7–10, 14).
An evaluation of indoor pollutants as risk factors for respiratory diseases requires costly and complex
methods that are difficult to implement in large populations. Building typology refers to the
documentation of a set of buildings with similarities in their type forms. Formal building typology may be
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based on configuration, format, or relationships of building to streets. From the perspective of
epidemiological studies, one can identify the types simply by simple observation of the common
buildings in a place. Among the seven types of houses in the South of Vietnam, there are five types
without any mechanical ventilation (15), suggesting that inhabitants of those house types could be
exposed to a higher level of indoor pollution leading to health risks.
We hypothesized that the concentrations of several indoor pollutants were associated with the type of
building and consequently that the house typology can be used as a global risk factor for chronic
respiratory diseases. In the present study, we measured and compared several indoor environment
parameters from the 5 types in 100 houses.
2. Methods
2.1 House types
Definitions
based on typology analysis, 5 types of dwellings were selected. The rental house (REN) is just a single
room for rent for all indoor activities. Each rental house is separate from others, with or without a garret
and has only a ground floor. The rural house (RUR) is a popular house type in the rural area, it has only a
ground floor but it has yards all around and the kitchen room is inside or outside. The slum house (SLU)
is a precarious, poor, and unsanitary housing without running water. It is usually found along the city’s
canal. The tube house (TUB) has at least 2 floors, the houses lie next to a house, and they are small in
width and large in depth. The apartment (APA) is a room or a group of related rooms, among similar sets
in one building, designed for use as a dwelling. Both APA and TUB look like multistorey buildings with 3
to 5 floors. In the study, only the old-style apartments were selected. All studied houses do not have a
modern or mechanical ventilation system. (see Fig. 1). A detailed description is available in a previous
paper (15).
The selection of the houses followed the WHO 30-cluster sampling method (16). From the 24 districts of
Ho Chi Minh City (HCMC), we included a total of 100 houses, based on a selection using a random table,
distributed between the studied 5 house types.
2.2 Indoor environment parameters:
Measured parameters: air temperature and RH, CO, CO2, VOC, and airborne concentration of PM2.5. A
sample of settled dust was obtained for endotoxin concentration measurement; it is considered
representative of the airborne level. (Heinrich et al., 2003; Park et al., 2006, 2000)
Equipment and procedure: the parameters of the air were measured every 1 minute for 36 hours, by the
multi-pollutants environmental monitor (3M-Quest EVM7, yearly calibration certified). A calibration check
and zero set were both performed before starting the measuring campaign in each new house. The
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minimum measurable value and the accuracy of the parameters are : CO (1 ppm; 2–5%); CO2 (1 ppm;
±100ppm at 200C); PM2.5 0.001 µg/m3); VOC (1 ppb; 2–5%); RH (0.1%; ±5%) and temperature (0,10C;
±1.10C)
In each house, we placed the multi-pollutant environmental monitor at the centre of the house (i.e. the
living room, on furniture with good airflow and far away from any heating source to avoid confounding
factors). Then, we collected three settled dust samples, from the living room, bedroom, and kitchen. Dust
samples were collected by a handled vacuum cleaner (Electrolux, China) with a cloth filter for 5 minutes.
Each sample of dust was stored at -20oC until extraction.
The principle of measuring air parameters:
1. Particulates: The EVM7 uses a laser-photometer that measures and stores concentration levels of
airborne dust over time. It is designed to measure the air pollutants, existing as matter (gases and
aerosols) in the environment. The particle size selector on the EVM filters out all particulates at or
above the selected size. We used the option 2.5µm (one of four settings). Real-time dust
concentration was measured by 90° optical light scattering photometer inside the EVM.
2. CO, VOC, and CO2: were measured by using a sensor technology that includes automatic sensor
recognition, calibration levels, and temperature compensation information as a consequence the
airflow from the CO sensor to the VOC sensor and then, the CO2 sensor.
3. Temperature and relative humidity: measured according to the airflow move into the EVM with the
separate sensor.
Endotoxin extraction and measurement: Dust extraction was carried out with pyrogen-free water (LONZA,
USA) (1mg fine dust in 5 mL water with a vortex device). After centrifugation, we measured endotoxin in
the dust-extracted solution immediately. The endotoxin assay method was published previously
(Bouillard et al.)(17) and it was based on the Kinetic Chromogenic LAL Assay. Besides, we also used a
beta-1,3-glucan blocker (LONZA, USA) to avoid the activation effect of glucan inside the dust sample. The
sensitivity of endotoxin detection is 0.005 EU/mL and it was expressed as Endotoxin Unit per milligram
dust (EU/mg).
2.3 Statistics: We transformed data by logarithm 10 for non-normal distribution data and reported each
parameter as geometric mean and 95%CI of the mean. With each parameter, we used ANOVA one-way
test to find differences among five house types. Later, we used post-hoc tests to compare each pair of
houses. All data were recorded in Excel 2010 and analyzed by SPSS 22.0. We used a spider graph to
show the level of all parameters of all house types. A p-value < 0.05 was considered significant.
3. Results
Endotoxin concentrations in the dust from 100 houses ranged from 107.8 to 149.1 EU/mg. About IA
parameters, 97 houses were measured, and 5 houses were re-measured in another season with the
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environmental monitor so in total we collected 102 sets of complete measurements. Among those, 4
results of VOC were rejected because of sensor error; we consider only 98 VOC results as acceptable. The
results of measured indoor environmental parameters (IEP) were shown in Table 1. The average value of
each parameter was calculated in each house and the minimum/maximum values were given in Table
1.Because at night, indoor activities were limited, we also compared the maximum values for the peak of
each parameter between the day and the night (defined as the time from 11:00 PM to 7:00 AM). In Table
1, we presented the geometric mean (GM) of the measurements during 36 hours for each parameter
among 100 houses. The minimum and maximum values correspond to the geometric means. The
absolute minimum value or maximum value shows the peak of the measured values during 36 hours.
Table 1
Characteristic of environmental parameters in 97 houses in Ho Chi Minh City.
Parameters
(unit)
N
Geometric
mean
Minimum
Maximum
(95% CI)
Maximum
Maximum
(Absolute
36h)
(Absolute
nighttime)
Pvalue*
CO (ppm)
102
2.37 (2.11–
2.67)
0.0
10.608
56
27
0.003
CO2 (ppm)
102
485.1
(469.0–
501.6)
356.0
1037.6
2265
2247
0.0001
PM2.5
102
23.2 (18.4–
29.2)
0.0
545.0
6.419
3.602
0.289
VOCs (ppb)
98
70.4 (44.0–
112.6)
0.0
3593.2
26104
9238
0.061
Temp (oC)
102
30.0 (29.7–
30.4)
30.3
34.8
38.9
34.4
0.025
RH (%)
102
60.5 (59.4–
61.7)
47.9
75.8
85.9
84.7
0.234
Endotoxin LIV
(EU/mg)
100
107.8
(100.3–
115.2)
5.94
1537.0
-
-
0.002
Endotoxin
BED (EU/mg)
100
124.5
(117.5–
131.6)
4.43
6720.0
-
-
0.0001
Endotoxin KIT
(EU/mg)
100
149.1
(140.5–
157.7)
3.5
4983.5
-
-
0.0001
(µg/m3)
LIV: living room; BED: bedroom; KIT: kitchen.
* P-value of Anova one-way test for the geometric mean of each parameter.
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For each IEP, we found some statistical differences among the 5 house types. They are statistically
different in levels of CO, CO2, and temperature. They are also different in settled dust endotoxin
concentration in the living room, in the bedroom and in the kitchen
Comparisons of each parameter related to the house types were shown in Fig. 2. The CO level was lower
in RUR compared to TUB, REN, and SLU. The CO2 level was higher in REN compared to TUB, SLU and
RUR. PM2.5 levels were similar in the 5 house types. The VOC concentration was lower in RUR compared
to REN and TUB. For physical parameters only temperature was higher in REN compared to RUR (see
Fig. 2). in RUR compared to TUB, REN, and SLU, although the difference in VOC among house types is not
strong (see Table 1).
The endotoxin concentrations in the dust from each room were shown in Fig. 3. The distribution of the
concentrations was similar in each room, regarding the house type. Though the kitchen of RUR was a
particularly high source of endotoxin, reaching 490 EU/mg (485.9-494.3). The APA and TUB were
comparable, both being the less contaminated dwellings compared to REN, SLU, and RUR. The REN type
was more contaminated compared to APA and TUB, though it was less than SLU and RUR.
The combined distribution of all parameters was shown in Fig. 4. The spider graph showed the
distribution of IEP was different from house type to house type. The IE models of the five house types
were different. The figure shows a higher surface for RUR and SLU compared to APA and TUB, while REN
was intermediate.
During the year, the weather of HCMC is characterized by two climatic seasons: the rainy (May to
November) and dry (December to April) seasons. Though, the evaluation of the 5 types of houses was not
associated with the season.
4. Discussion
There are not many reports on the in-home environment quality in South East Asia, most researches
focus on outdoor air pollutants (12). This study is the first report describing the indoor environment
quality in the South of Viet Nam. The level of the observed indoor environmental pollution (IEP) of houses
measured in HCMC was higher than in Taiwan (18), Korea (Kim et al, 2002), Japan (19), Thailand and
Singapore(20) and of western countries (21–23) but it was lower than in China (24) (Jim et al, 2006)
(Fischer et al, 2007). The mean endotoxin concentration is also higher than in the other studies.
Endotoxin level in Taiwanese homes reaches 108.4 EU/mg (18). In western countries, indoor endotoxin
levels are mostly under 20 EU/mg (25–27). In general, the concentrations of studied IEP in Vietnamese
homes remain within the recommended range, except for the VOC level and the temperature (higher than
recommended). Measured PM2.5 levels nearly reach the upper recommended limits (23 vs. 25 µg/m3)
(28–30). Although indoor endotoxin’s lower limit for human health protection is unknown, endotoxin
present in settled dust in Vietnamese homes seems very high (31). This fosters the recommendation
towards the IEP improvement to reduce health risks and related diseases. Previous studies on indoor air
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characteristics have not question the role of home types in the pollutants accumulation in the home.
Therefore, we aim to demonstrate that a specific attention should be paid to house types when
comparing indoor environment quality between geographical areas.
According to our data, the measured levels of several parameters are not equally distributed among
different house types. This could be attributed to differences in dwelling construction or pollutant source
usage(32, 33). Depending on the measured parameter related to the indoor environment, the higher health
risk are encountered in RUR, REN and SLU dwelling types are regarding endotoxin, in REN dwelling types
considering CO2, CO, VOC, and SLU when it comes to PM2.5).
A study in India found that the indoor CO level is similar in rural houses (1.2 ± 0.4 mg/m3) and urban
houses (1.2 ± 0.3 mg/m3) (34). Shezi et al. reported that building construction and ventilation status, in
African homes, are associated to a difference in PM2.5 concentration. They also use the type of house in
a predictive model to estimate the in-home PM2.5 concentration (35).
Some studies reported that the endotoxin level in non-farming homes is lower than in farming ones (36).
The Thai and Singapore studies found similar results (20). We also compared endotoxin concentrations
among the five house types, room by room. In the same type of room, the difference in endotoxin levels
was related to the type of dwelling’s role. Other studies in Europe suggested that the type and the location
of the dwelling should be recorded while evaluating the indoor endotoxin level (37).
Our research has shown that IEP is different among housing types. The differences could be explained by
the airflow caused by the structure of the house. A study showed that the indoor air quality and the
ventilation of the house are influenced by the indoor pollution sources whether are related to residual
activities or continuous emissions. The ventilation rate is inversely correlated with the concentration of
indoor pollutants (38).
Housing ventilation is one of the aspects that could explain the differences in indoor environmental
quality in addition to other factors such as indoor activities and the presence of pollution sources. In this
study, the difference in CO2 levels among the five house types supported the hypothesis. Moreover, the
CO2 level is often used as a ventilation evaluation indicator. Besides indoor activities, the differences in
temperature and air exchange (house construction) could contribute to the differences in VOC levels
between REN (the highest VOC level house type) and RUR (the lowest one) in our study as shown by other
researchers (39). VOC concentrations in dwellings are influenced by temperature, humidity and air
exchange rate (9).
Most kitchens in RUR are located outdoors or present a back door or windows. This could lead to a lower
CO level in RUR than in the other house types. CO concentration could be affected by the ventilation
status of the burning place (kitchen) (32).
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From our data, the average CO2 concentration was lower in RUR than in REN, SLU, and TUB. The
difference in the CO2 level between rural houses and urban houses could be caused by ventilation
problems and indoor cooking without a chimney in urban houses. Even though, the number of people
living in urban houses is often lower than in rural houses. RUR's kitchen is usually at the end of the house
or outdoors (at the back of the house) while the measuring equipment was positioned in the living room
area. This suggests that the kitchen’s PM2.5 level could even be higher than the measured value. The
endotoxin level in the kitchen of RUR is also very high. The combination of high levels of endotoxin and
PM2.5 could increase risk of CRD in those dwellings.
REN is a very small and cramped house type. It presents the highest CO2 level because it is usually built
with a small window or even without any. The inhabitants (source of CO2) live in a small square.
SLU and REN are similar in characteristics, with only one small door, sometimes a small window, both in
the same direction and no other outlet. With this structure, incoming and outgoing air can lead to an
accumulation of the pollutants within this type of house. The location could explain the differences
between SLU and REN. SLU are located along the canal (with water underneath the houses), constructed
of semi-permanent materials and with holes or openings on the walls. SLU is usually located along
canals and in direct contact with the roads, in consequence it presents the highest level of PM2.5 (28).
Therefore, it is far more influenced by the outdoor PM2.5 emissions next to the traffic.
Often TUB present closed windows and closed doors to avoid the outside dust. Studies have confirmed
that in homes with windows opened for more than half an hour per day in different rooms, the CO2 and
benzene levels are significantly lower than those with never or rarely-opened windows (28, 40). Although,
the IA quality of TUB is better than REN and APA, it has the highest level of CO and is nearly equal to REN
about VOC. This shows that the building structure and the activities should also be recorded.
APA seems to have the best indoor environment quality score. APA is generally located higher than other
house types. It is less influenced by street-level car-based outdoor pollution. APA has a low population
density. APA has windows and doors on the front and back of the home. A study in French houses, on
indoor Radon, showed that the building type and the floor level play a role in the pollutant’s distribution
(41). Another study also identified the role of the building type and the floor level in indoor allergen
distribution (42).
In this study, we made the hypothesis that the floor level would not affect our study results because the
studied APA and TUB have 2–5 floors. This study did not include the modern and over-5-floors APA.
Kyung Hwa Jung et al. reported a difference in indoor air quality (black carbon, PM2.5 and VOC) between
the 6th-32nd floor group and the lower floor groups 38. This difference was caused by the traffic. However,
there was no difference between the 0-2nd floor group and the 3rd-5th floor group (43). On the other hand,
we were careful in not selecting houses or apartments near the highway, factory, industrial zone or
crowded traffic street.
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We did not measure the outdoor air parameters. By selecting the studied houses in one city and not close
to highways, factory, industrial zone or crowded traffic street, we tried to limit the effects of the outdoor
environment on the measured indoor air parameters. We made the hypothesis that the outdoor
environment of the studied houses was nearly similar. This allowed us to define the differences in indoor
air parameters among five studied house types with limited effect from the outdoor environments.
Our research is done with real-time repetitive measurements. We limited the choice of measured
parameters considering availability of equipment and minimum inhabitants’ disturbance. However, the
parameters we measure are from the living room of the house (the main living area) so it could not fully
be reflecting the situation in the air in different locations. We also try to minimize the impact of airborne
noise by not selecting homes near the highway, away from factories and industrial parks, even if we did
not measure noise.
5. Conclusions
This is the first study of the environmental characterization of indoor pollution in five typical house types
in HCMC. The results show a difference in patterns of parameters in the house types. REN and RUR are
the most different. For most parameters, REN presents a higher concentration than the other house types,
although the differences are not statistically significant. However, RUR and SLU presented higher PM2.5
concentrations. In a later phase, the indoor air characteristics will be confronted with the prevalence of
CRD in the 5 chosen house types which could contribute to public health intervention (remove or decrease
the environmental risks of chronic respiratory diseases).
Abbreviations
APA
apartment
BED
bedroom
CI
confidence interval
CO
carbon monoxide
CO2
carbon dioxide
CRD
chronic respiratory diseases
KIT
kitchen
HCMC
Ho Chi Minh city
Page 9/18
IA
indoor air
IE
indoor environment
IEP
indoor environmental parameters
LIV
living room
PM2.5
particulate matter under 2.5 micrometres
REN
rental house
RH
relative humidity
RUR
rural house
TUB
tube house
VOC
volatile organic compounds
WHO
World Health Organization
Declarations
Ethics approval and consent to participate: This study was a part of the larger study (The
relationship between environmental risk factors in housing types and prevalence of chronic
respiratory diseases) which was approved by Ethics Committee of Pham Ngoc Thach University of
Medicine (approval number CS.2015.04).
Consent for publication: Not applicable.
Availability of data and materials: The datasets generated and/or analysed during the current study
are not publicly available due it is only accessed by the project researchers as inform consent’s
content and it is using for the further study that we intent to report soon. But are available from the
corresponding author on reasonable request. private data in agreement with informed consent form
signed by participants
Competing interests: We declare no conflict of interest.
Funding: This study has been supported by Partenariat Interuniversitaire Ciblé
(ref http://www.cud.be/content/view/1013/504/lang,/) granted from the ARES (Académie de
Recherche et d’Enseignement Supérieur) of Belgium.
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Authors' contributions: TNT, DKTN and TTTT were responsible for data collection under the technic
supports from CB, JMH and funding support from OM. TNT analyzed and interpreted the row data
regarding the studied houses. CB, OM support to interpreted and checked the results. TNT and CB
major contributor in writing the manuscript. All authors read and approved the final manuscript.
Acknowledgements: This study has been supported by a Projet Interuniversitaire Ciblé (PIC), from
2012 to 2016, between the Université Libre de Bruxelles (ULB) and the Pham Ngoc Thach University
(U-PNT). [PIC-CUD 2012-2016]
Authors' information (optional):
1. Thanh Ngoc TRAN: Medical Doctor, Master in Medicine. Lecturer & Physician. Deputy head of
department of Physiology, Patho-Physiology and Immunology. Deputy head of Post-Graduate
Department. Pham Ngoc Thach University of Medicine. Address: 02 Duong Quang Trung, Ward 12,
District 10, Ho Chi Minh city, Vietnam.
Contact: dr.tranngocthanh@pnt.edu.vn or dr.tranngocthanh@gmail.com.
2. Thuy Thu Thi TRAN: Doctor in Environmental Science. Lecturer of Industrial University of Ho Chi
Minh city. Contact: tranthithuthuy.hui@gmail.com,
3. Diem Kieu Thi NGUYEN: Master in Environmental Science. Lecturer of Industrial University of Ho Chi
Minh city. Contact: nguyenthikieudiem@hui.edu.vn
4. Jean-Marie HAUGLUSTAINE: Professor. Dean of Faculté des Sciences
Département des sciences et gestion de l'environnement (Arlon Campus Environnement). Bât. BE-009
DER Sc. et gest. de l'environ. (Arlon Campus Environ.)
avenue de Longwy 185. 6700 Arlon. Belgium. Contact: jmhauglustaine@uliege.be
5. Olivier MICHEL: Professor. Faculty of BioMedicine. Université Libre de Bruxelles (ULB), Belgium. Dean
of Clinical Immunoallergology Department of Brugmann Hospital, Brussels. Belgium. Contact:
olivier.michel@ulb.be
6. Cathetine BOULAND: Professor. President of the School of Public Health. Director of Research Center
of Environmental Health and Working Health. Free University of Brussels (ULB), Belgium. Address:
ULB - Ecole de Santé Publique CP593. route de Lennik 808, 1070 Bruxelles. Contact:
catherine.bouland@ulb.be
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Figures
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Figure 1
Photograph of the 5 typical house types in Ho Chi Minh City.
a) apartment, b) rental house, c) rural house, d) slum house and e) tube house
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Figure 2
Characteristic of indoor air parameters in five house types of HCMC. a) Carbon monoxide (ppm); b)
Carbon dioxide (ppm); c) PM2.5 (μg/m3); d) VOCs (ppb); e) Temperature (oC); f) Humidity (%). * p<0.05;
** p<0.01 with ANOVA one-way test.
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Figure 3
Distribution of settled dust endotoxin concentration (EU/mg) in each room type among five house types.
a) In living room; b) In bedroom; c) In kitchen. * p<0.05 with ANOVA one-way test
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Figure 4
Comparison of all indoor environment parameters among five house types in Ho Chi Minh city. Unit of
each axis is percent. APA: apartment; REN: rental house; RUR: rural house; SLU: slum house; TUB: tube
house. * p<0.0001; ** p < 0.01; *** p<0.05; **** p <0.1.
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