Indoor air pollution and the health of children in biomass- and fossil-fuel users of Bangladesh: situation in two different seasons
Environ Health Prev Med
Indoor air pollution and the health of children in biomass- and fossil-fuel users of Bangladesh: situation in two different seasons
Md. Khalequzzaman 0 1 2 3
Michihiro Kamijima 0 1 2 3
Kiyoshi Sakai 0 1 2 3
Bilqis Amin Hoque 0 1 2 3
Tamie Nakajima 0 1 2 3
0 K. Sakai Nagoya City Public Health Research Institute , Nagoya , Japan
1 M. Kamijima (&) Department of Occupational and Environmental Health, Nagoya City University Graduate School of Medical Sciences , 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601 , Japan
2 Md. Khalequzzaman T. Nakajima Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine , Nagoya , Japan
3 B. A. Hoque Environment and Population Research Center (EPRC) , Dhaka , Bangladesh
Objectives Indoor air pollution levels are reported to be higher with biomass fuel, and a number of respiratory diseases in children are associated with pollution from burning such fuel. However, little is known about the situation in developing countries. The aim of the study was to compare indoor air pollution levels and prevalence of symptoms in children between biomass- and fossil-fuelusing households in different seasons in Bangladesh. Methods We conducted a cross-sectional study among biomass- (n = 42) and fossil-fuel (n = 66) users having children \5 years in Moulvibazar and Dhaka, Bangladesh. Health-related information of one child from each family was retrieved once in winter (January 2008) and once in summer (June 2008). The measured pollutants were carbon monoxide (CO), carbon dioxide (CO2), dust particles, volatile organic compounds (VOCs), and nitrogen dioxide. Results Mean concentration of dust particles and geometric mean concentrations of VOCs such as benzene,
Indoor air pollution; Environmental; Bangladesh; Health; Children
toluene, and xylene, which were significantly higher in
biomass- than fossil-fuel-users’ kitchens (p \ 0.05), were
significantly higher in winter than in summer (p \ 0.05).
Levels of CO and CO2, which were significantly higher in
biomass than fossil-fuel users (p \ 0.05), were
significantly higher in summer than winter (p \ 0.05). However,
no significant difference was found in the occurrence of
symptoms between biomass- and fossil-fuel users either in
winter or in summer.
Conclusions It was suggested that the measured indoor
air pollution did not directly result in symptoms among
children. Other factors may be involved.
Approximately 50% of the world’s population and up to 90%
of rural households use biomass fuels as a domestic source of
energy in the form of wood, crop residues, and animal dung
]. Cooking and heating with such solid fuels is the major
source of indoor air pollution and pollution levels that exceed
the standard allowable limits in developing countries [
Polluted indoor air contains a range of health-damaging
pollutants, such as particulate matter, carbon monoxide
(CO), carbon dioxide (CO2), nitrogen dioxide (NO2), sulfur
dioxide (SO2), and volatile organic compounds (VOCs)
]. These pollutants are able to cross the alveolar–capillary
barrier and penetrate deep into the lungs [
]. Thus, the
pollutants pose a risk for a number of respiratory diseases,
such as acute respiratory tract infection (ARTI), chronic
obstructive pulmonary disease (COPD), tuberculosis, and
asthma, as well as for low birth weight, cataracts, and
]. The World Health Organization (WHO) has
listed indoor air pollution from burning of biomass fuel as
one of the top ten global health risks, as it is responsible for
2.7% of the global burden of disease . Especially for
women and children, who spend the most time indoors
during fuel burning, levels of exposure to polluted air are
reported to be higher [
]. Every year, 1.5–2 million deaths
worldwide are attributed to indoor air pollution [
1 million of which take the lives of children\5 years old due
to ARTI but also of women due to COPD and lung cancer
. ARTI accounts for 19% of the total deaths in children
\5 years old, making it the second most common cause of
death in that age group [
Bangladesh is located in the northeastern part of south
Asia. From March to June, the country experiences a hot
summer season with high humidity and from November to
the end of February, a cool, dry winter. For their domestic
source of energy, 92% of Bangladesh’s people depend on
biomass fuel [
]. Indoor air pollution is responsible for an
estimated 3.6% of the overall disease burden in the country
]. About 25% of deaths among children \5 years old in
Bangladesh is associated with ARTI [
]. Switching from
biomass to fossil fuel is thus encouraged in Bangladesh, as
pollution levels are believed to be higher with biomass fuel.
Little is known about the situation in developing countries.
In our previous study, we found the level of indoor air
pollutants was higher in fossil fuel than in biomass fuel,
but the prevalence of some respiratory symptoms was
significantly higher in biomass-fuel users’ children [
Disagreement of our findings with most other studies
encouraged us to conduct further study to clarify the seasonal
difference as a possible confounding factor in pollution level,
as well as the prevalence of symptoms. Some studies have
suggested that the level of indoor air pollutants, especially
VOCs, were the highest in winter and the lowest in summer
]. Thus, we planned to conduct a cross-sectional study
in Bangladesh among the biomass- and fossil-fuel users in
two different seasons, winter and summer. The purpose of
the study was to compare the indoor air pollution levels and
prevalence of symptoms in children between biomass- and
fossil-fuel-using households in different seasons in
Bangladesh. By comparisons between seasons, we aimed to clarify
whether a seasonal difference may play a role in the levels of
indoor air pollution and the prevalence of respiratory
symptoms in children in a developing country.
A cross-sectional study was conducted among
biomassand fossil-fuel users of urban Dhaka and urban
Moulvibazar in Bangladesh: once in winter (January) and
once in summer (June) 2008. There was socioeconomic
and cultural proximity between the inhabitants of both
areas. We found that both the biomass- and fossil-fuel users
coexist in those areas. As there was natural gas supply in
those areas and the gas users pay a fixed amount of money
for the whole month, the number of biomass-fuel users was
less compared with gas users. The areas were densely
populated, and houses were very close to each other and in
a cluster, separated by narrow roads. We asked if there was
any child \5 years old in the household and if they agreed
to participate in the study. If the answers were positive, we
included them. This procedure was repeated in every house
in the selected clusters until the targeted number of
households (approximately 40 for each fuel type) was
recruited. As a result, 42 biomass- and 66 fossil-fuel-using
families with children \5 years of age (range 0–5 years)
were selected. Most biomass-fuel users used wood as a
cooking fuel, whereas fossil-fuel users employed only gas.
Sociodemographic data of the respondents using
questionnaires and observation checklists were collected from
mothers of the children. Air pollution data were collected
once in winter and once in summer. For gathering the
health-related information of the children, one child from
each household was taken into consideration. To apply the
same selection rule throughout recruitment, we considered
the oldest child when the number of eligible children was
more than one. Symptom-related information of the
children for the previous 1 month was collected from mothers
using the questionnaire during interview. This study was
conducted with all participants’ informed consent and was
approved by the ethical committee of Nagoya University
Graduate School of Medicine.
Monitoring indoor air quality
Temperature, humidity, levels of CO, CO2, and dust
particles were measured in the kitchen during interviews with
the respondents. CO and CO2 concentrations were
measured with detector tubes (type 106SC for CO and type
126SF for CO2, Komyo Rikagaku Kogyo, Kawasaki,
Japan) for 4 and 2 min, respectively. Concentrations of
dust particles were measured with a digital dust monitor
(model LD-3, Sibata Scientific Technology, Tokyo, Japan),
and the mean of five 1-min measurements was used for
statistical analysis. As the air quality of the kitchen was
measured during interviewing and the cooking time was
different from household to household, some mothers were
cooking and others were not at the time of our visit.
Formaldehyde (HCHO) and nitrogen dioxide (NO2) were
collected using a diffusion sampler packed with silica gel
containing triethanolamine (passive gas tube for HCHO
and NO2; Sibata Scientific Technology). A diffusion
sampler packed with activated charcoal (passive gas tube
for organic solvents; Sibata Scientific Technology) was
used for collecting 14 VOCs. The samplers were placed for
approximately 24 h in the kitchen at a height of 80–90 cm,
which is the average breathing height of children \5 years
old. The households we studied were in clusters, and we
assumed that the outdoor air pollutant concentrations of
one household from one cluster were representative of
other households of that cluster. Thus, we decided to
measure the outdoor concentrations of one household from
Samplers used in Bangladesh were transported to Japan by
air and analyzed by the same researchers. HCHO and NO2
were extracted with distilled water and analyzed using
spectrophotometry by the
4-amino-3-hydrazino-5-mercapto-1,2,4-triazole method and the sulfanilamide method,
]. VOCs were analyzed by the method
reported by Sakai et al. [
]. Briefly, the adsorbent in the
diffusive sampler was transferred into 7-ml vials, and 2-ml
carbon disulfide (CS2 to assess the working environment,
Wako Pure Chemical Industries, Japan) was added. The
vials were then shaken, left for 2 h, and centrifuged for
10 min at 3,000 rpm. One milliliter of a supernatant added
with 5 ll of an internal standard solution (200 lg/ml,
toluene-d8, Aldrich, USA) was then analyzed by a gas
chromatograph with a mass spectrometer (GC–MS). The
GC–MS (5980 Series II/5971A, Hewlett Packard, USA)
was equipped with a 60 m 9 0.25 mm i.d. capillary
column coated with a 1.5-lm film of NB-1 (GL Sciences,
Japan). The GC oven temperature was first maintained at
45 C for 5 min then programmed to 300 C at 10 C/min
and maintained at 300 C for 7 min. For some samples, the
analysis was performed under a total-ion-monitoring mode
to examine all major peaks after selected-ion-monitoring
mode targeting 14 VOCs.
Pollutant concentrations, temperature, and humidity
between biomass and fossil fuels were statistically
compared by Student’s t test after appropriate transformation
of variables, if necessary. Frequencies of findings were
compared using Fisher’s exact test. When comparing
between biomass and fossil fuels based on measurement
during cooking or noncooking time, a two-way analysis of
variance (ANOVA) was performed to calculate
significance. Mann–Whitney U test was performed for
calculating the significance of monthly income. A two-tailed
p value \0.05 was considered to indicate a statistically
significant difference. The mean concentrations of 14 VOCs,
HCHO, and NO2, which were approximately log-normally
distributed, were calculated as geometric mean. When the
concentrations were below the detection limit, they
were set at half of the detection limit while calculating
the geometric means. By taking the biomass-fuel-users’
children as a control group, we clarified how much the
fossil-fuel-users’ children were at risk of suffering from
symptoms. In this regard, multivariate regression analysis
was conducted to estimate the crude and adjusted odd
ratios (ORs) and their 95% confidence intervals (95% CIs)
for children’s symptoms with/without adjustment for
potential confounders, including education, monthly
income, number of family members per room, frequency of
cooking, main wall material of house, main floor material
of house, and location of kitchen. Calculations were
performed with Statistical Package for the Social Sciences
(SPSS) for Windows, version 16.0 software (SPSS Inc.,
Chicago, IL, USA).
Table 1 describes the sociodemographic conditions of
respondents. Educational background was significantly
higher in fossil-fuel users than in biomass-fuel users
(p \ 0.01). The monthly income for fossil-fuel users was
significantly higher than the biomass-fuel users (p \ 0.01).
There was no significant difference in the number of family
members, but as the number of rooms was significantly
higher in fossil-fuel users (p \ 0.01), the number of family
members per room was significantly higher in biomass-fuel
users than fossil-fuel users (p \ 0.01). Considering kitchen
location, there was a significant difference between the
biomass- and fossil-fuel users (p \ 0.01). For biomass-fuel
users, 69% of the houses had a separate kitchen and in
contrast, 89% of the fossil-fuel users did not have a kitchen
separate from the house. In fossil-fuel users, a significantly
higher percentage of houses (62%) cooked three times per
day compared with biomass-fuel users, where 62% of houses
cooked twice a day (p \ 0.01). Thus, there was a significant
difference in the mean cooking hours between fossil- (3.3 h/
day) and biomass-(2.8 h/day)-fuel users (p \ 0.01).
The house and kitchen characteristics of the respondents
are shown in Table 2. There was a significant difference in
the type of main roof, wall, and floor materials between
biomass- and fossil-fuel-user houses and kitchens
(p \ 0.01). For roofs and walls, biomass-fuel users’ houses
and kitchens were mainly of tin, whereas those fossil-fuel
users were made of concrete and brick. A large number of
biomass-fuel users’ houses and kitchen floors were made of
mud, whereas fossil-fuel users employed concrete.
Temperature, humidity, CO, CO2, and dust particles are
shown in Table 3. Considering the time of measurement,
the level of CO in a fossil-fuel-using kitchen in winter, and
the humidity and CO levels in a biomass-fuel-using kitchen
in summer were significantly higher during cooking than at
other times (p \ 0.05). Levels of humidity, CO, dust
particles, in winter and humidity, CO, CO2, and dust particles
in summer were significantly higher in the
biomass-fuelusing kitchen than the fossil-fuel-using kitchen, both
during cooking and at other times (p \ 0.05). Levels of CO
and CO2 in biomass-fuel-users’ kitchen measured during
cooking were significantly lower in winter than summer
(p \ 0.05). There was a significant difference in the level
of dust particles in biomass-fuel kitchens measured during
noncooking times and fossil kitchens during cooking
(p \ 0.05). They were both higher in winter.
Airborne concentrations of VOCs and NO2 are
displayed in Table 4. In winter, the geometric mean indoor
concentrations of hexane, benzene, toluene, xylene, and
tetrachloroethylene were significantly higher in
biomassfuel-using than in fossil-fuel-using kitchens (p \ 0.05). But
the level of formaldehyde was significantly higher with
fossil fuel than biomass fuel (p \ 0.05). In summer, levels
of benzene, toluene, and xylene were significantly higher in
biomass- than fossil-fuel-using kitchens (p \ 0.05). The
outdoor concentrations of hexane, benzene, toluene, and
NO2 were also significantly higher in biomass- than
fossilfuel users both in winter and summer (p \ 0.05). In
addition, the levels of xylene, tetrachloroethylene, and methyl
ethyl ketone were significantly higher in biomass- than
fossil-fuel users outdoors during winter (p \ 0.05).
Geometric mean outdoor concentrations of benzene, xylene,
tetrachloroethylene, and methyl ethyl ketone in
biomassfuel users, and NO2 in fossil-fuel users outdoors were
significantly higher in winter than summer (p \ 0.05).
During cookinga (n = 51)
Biomass (n = 18)
During noncookinga (n = 57)
Fossil (n = 33)
Biomass (n = 24)
Fossil (n = 33)
Main wall material of house
Main wall material of house
Number of family members
Number of family members
Location of kitchen
Main wall material of house,
location of kitchen
Main wall material of house
OR odds ratio, 95% CI 95% confidence interval, NC not calculated due to small number
a Number of children observed at biomass- and fossil-fuel users was 42 and 66, respectively
b Adjusted for education, monthly income, number of family members per room, frequency of cooking, main wall material of house, main floor
material of house, location of kitchen
Hexane levels in fossil-fuel users outdoors were
significantly higher in summer than in winter (p \ 0.05).
In Table 5, the prevalence of symptoms and signs of
children \5 years in both winter and summer is shown.
Crude ORs show that there was no significant difference in
the occurrence of symptoms between children of
biomassand fossil-fuel users in both winter and summer. After
adjustment with the potential confounders, the result
remained the same. However, in winter, we found a
significant association of the main wall material of houses with eye
itchiness and shortness of breath, education with skin
itchiness and diarrhea, and frequency of cooking with skin
itchiness. In summer, results show association between the
number of family members per room with eye redness and
eye itchiness, location of kitchen with runny nose and cough,
and main wall material with cough and shortness of breath.
We measured the pollutant concentrations of CO, CO2,
and dust particles during the interviews. Airborne
concentrations of these pollutants were significantly higher
in biomass-fuel-users’ than fossil-fuel-users’ kitchens at
different measured times, which is consistent with the
findings of other studies [
]. Considering the seasonal
variation, we found a significant difference in the levels of
dust particles and CO between winter and summer. The
mean concentrations of dust particles in winter and CO in
summer were significantly higher, even much higher than
the standard allowable limits (0.1 mg/m3 for dust particles,
and 7.6 ppm for CO) mentioned by the United Nations
Development Program/Department of Economic and
Social Affairs/World Energy Council (UNDP/DESA/
WEC) World Energy Statement . The possible reason
behind the higher concentration of dust particles may be
the dry, less humid weather in winter. In the wet summer,
because of the significantly higher humidity, biomass-fuel
users very often use less dried wood for cooking.
Incomplete wood combustion might explain the high CO
concentration in biomass-fuel use in summer.
Except for formaldehyde in winter, 24-h airborne
concentrations of major VOCs, such as benzene, toluene,
and xylene, were significantly higher in biomass- than in
fossil-fuel-users’ kitchens both in winter and summer.
However, toluene and xylene levels were much lower than
the guideline value of 260 lg/m3 for toluene and 870 lg/
m3 for xylene set for Japan [
]. The levels of benzene and
xylene were higher in winter than in summer. Some other
studies also found the same seasonal difference [
Ventilation might be a key factor in our study regarding the
higher concentrations in winter. The natural ventilation was
poorer in winter because dwellers kept doors and windows
closed. Outdoors, there was a similar trend in the levels of
VOCs. For some pollutants in biomass-fuel use,
concentrations outdoors were even higher than in the kitchen.
Thus, indoor air in those households could be contaminated
by outdoor air pollutants. In contrast with our study, we
obtained significantly higher VOC concentrations for
fossil-fuel users than biomass-fuel users in our previous study
], presumably due to socioeconomic differences with
biomass-fuel users in the studies. Biomass-fuel users in our
previous study were poorer than those in this study.
Kitchens of biomass-fuel users in this investigation were
made with a mixture of tin, brick, and bamboo; almost all
kitchens in our previously studied biomass-fuel users were
of bamboo. There were many broken parts in those kitchen
walls, which facilitated natural ventilation. Moreover,
research revealed that concentrations of pollutants in the
houses dramatically decrease within an hour of cooking,
when ventilation is common [
Many studies have shown a positive association between
the higher concentrations of indoor air pollutants from
biomass-fuel users and the occurrence of respiratory
diseases, especially in children \5 years of age. WHO/UNDP
stated that indoor air pollution doubles the risk of
pneumonia in children \5 years [
]. A significant association of
cooking smoke from biomass-fuel combustion with the
prevalence of asthma (OR = 2.20; 95% CI = 1.2–4.2) and
other respiratory diseases in young children was observed
by Mishra [
]. A study conducted on children aged 4–
6 years in Guatemala showed the higher prevalence of
asthmatic symptoms in biomass-fuel-using households,
with ORs [2.0 [
]. In their prospective cohort study,
Etiler et al. [
] found a significant association between
symptoms of ARTI in infants and the use of biomass fuel
(RR = 1.8, 95% CI = 1.3–2.5). Awasthi et al. [
reported a significant positive association of respiratory
symptoms with the choice of biomass fuel (OR = 2.7, 95%
CI = 1.4–5.3). Other studies revealed the association of
exposure to indoor VOCs with respiratory diseases and
]. Some other studies also demonstrated a
positive relationship between air pollution from biomass
combustion and child health [
23, 24, 35, 36
]. In this study,
although in both winter and summer there were differences
in pollution levels with different fuel types, we noted no
such differences in the occurrence of respiratory symptoms
either in winter or summer. We could not establish an
association between the choice of fuel type and the
occurrence of respiratory symptoms in children \5 years.
This is consistent with our previous study finding, which
indicated no association between symptom occurrence and
fuel type [
]. The results of the study reported here is also
consistent with results of Wafuala et al. [
After adjustment with possible confounders, we found a
significant association of the main wall material of houses
with eye itchiness, cough, and shortness of breath. Whereas
the main wall material for fossil-fuel users was brick, tin
and bamboo were the choice of biomass-fuel users. Fungus
and mold growth tended to be higher with building
materials in biomass-fuel-users’ houses [
consistent associations between molds and respiratory
symptoms, with ORs ranging from 1.2 to 2.3, were reported
by other researchers [
]. Thus, exploration of the
possible role of fungus and molds should be incorporated
in future studies.
The levels of some indoor air pollutants were found to be
higher in biomass- than fossil-fuel-users’ homes both in
winter and summer. With some pollutants, indoor air was
more polluted in winter than in summer. There was no
difference in the prevalence of some symptoms among
children of biomass- and fossil-fuel users between winter
and summer. There was also no association between
measured indoor air pollution and prevalence of symptoms
among children \5 years in Bangladesh. Other factors may
Acknowledgments This study was partially supported by a
Grantin-aid for Scientific Research (B 19406020) from the Japan Society
for the Promotion of Science. The authors are grateful to the EPRC
staffs for their generous assistance in collecting as well as ensuring
the quality of data.
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