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BioScience Trends. 2012; 6(5):219-228. 219
Biomass fuel exposure and respiratory diseases in India
Rajendra Prasad
1,
*
, Abhijeet Singh
2
, Rajiv Garg
2
, Giridhar B. Hosmane
3
1
UP Rural Institute of Medical Sciences and Research, Safai, Etawah, India;
2
Department of Pulmonary Medicine, CSM Medical University, Lucknow, India;
3
Department of TB, Chest & Respiratory Diseases, KS Hegde Medical Academy, Mangalore, India.
*Address correspondence to:
Dr. Rajendra Prasad, UP Rural Institute of Medical
Sciences and Research, Safai, Etawah, India.
E-mail: rprasadkgmc@gmail.com
1. Introduction
One half of the world's population relies on biomass
fuel as the primary source of domestic energy (1).
Biomass fuel causes a high degree of morbidity and
mortality in humans. This is especially true in the
context of developing countries, which account for
99% of the world's biomass fuel use (2). Biomass
fuel consists of firewood, dung cakes, agricultural
crop residues (such as straw, grass, and shrubs), coal
fuels, and kerosene. Together, they supply 75% of the
domestic energy in India. The rest of the country relies
on cleaner fuels, namely liquified petroleum gas (LPG)
and natural gas.
2. Biomass fuel use in India
An estimated three-quarters of Indian households
use biomass fuel as the primary means for domestic
cooking. Ninety percent of rural households and 32% of
urban households cook their meals on a biomass stove.
Only 25% of the cooking is done with cleaner gases.
Ninety percent of households using biomass fuels cook
on an open fire. There are wide variations between rural
and urban households regarding the specific type of
biomass fuel used. In rural India, 62% of households
use firewood and 14% cook with dung cakes while
13% use straw, shrubs, grass and agricultural crop
residues to fire their stoves. In urban India, 22% use
firewood, 8% use kerosene, and the rest uses cleaner
fuels like LPG or natural gas (3). According to World
Health Organization, an estimated 58% of the Indian
Summary
One half of the world's population relies on biomass fuel as the primary source of domestic
energy. Biomass fuel exposure causes a high degree of morbidity and mortality in humans.
This is especially true in the context of developing countries, which account for 99% of the
world's biomass fuel use. Biomass fuel consists of fire wood, dung cakes, agricultural crop
residues such as straw, grass, and shrubs, coal fuels and kerosene. Together, they supply
75% of the domestic energy in India. An estimated three-quarters of Indian households
use biomass fuel as the primary means for domestic cooking. Ninety percent of rural
households and 32% of urban households cook their meals on a biomass stove. There
are wide variations between the rural and urban households regarding the specific type
of biomass fuel used. Globally, almost 2 million deaths per year are attributable to solid
fuel use, with more than 99% of these occurring in developing countries. Biomass fuel
accounts for 5-6% of the national burden of disease. Burning biomass fuels emits toxic
fumes into the air that consist of small solid particles, carbon monoxide, polyorganic and
polyaromatic hydrocarbons, and formaldehyde. Exposure to biomass fuels has been found
to be associated with many respiratory diseases such as acute lower respiratory infections,
chronic obstructive pulmonary disease, lung cancer, pulmonary tuberculosis, and asthma.
Biomass fuel exposure is closely related to the burden of disease in India. Hopes are that
future studies will examine the morbidity associated with biomass exposure and seek to
prevent it. Concerted efforts to improve stove design and transition to high-efficiency low-
emission fuels may reduce respiratory disease associated with biomass fuel exposure.
Keywords: Biomass fuels, chronic obstructive pulmonary disease (COPD), tuberculosis, cancer
DOI: 10.5582/bst.2012.v6.5.219
Review
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BioScience Trends. 2012; 6(5):219-228.
population depended on solid fuels for domestic use
in 2010 (4). Seventy-five percent of rural households
reported firewood as their primary cooking fuel as
compared to only 22% of urban households. Clearly,
factors such as affordability, education, availability,
constraints on cooking space, social customs, and
demographics (e.g. working women) play a significant
role in the choice of fuel in urban areas (5).
3. Morbidity and mortality
Globally, almost 2 million deaths per year are
attributable to solid fuel use, with more than 99%
of these occurring in developing countries (1). The
number of disability-adjusted life years (DALYs)
attributable to indoor air pollution from solid fuel for
all uses is calculated to be 40 million. India's figures
are very alarming. With a yearly death toll of 662,000
attributed to biomass fuel exposure, India tops the list
of fuel-related deaths in the South Asian region (2).
Biomass fuel attributes for 5-6% of the national burden
of disease (6). Indoor air pollution from solid fuel use
in all developing countries was estimated to account
for about 1.6 million deaths annually in 2004 and about
500,000 in India in 2010, suggesting a serious impact
on health (7,8).
4. Emissions from a biomass stove and exposure-
determining factors
When firewood (an essential biomass fuel) is burnt,
its combustion efficiency is far less than 100%. This
indicates that biomass fuels are at the high end of the
fuel ladder in terms of pollution emissions and at the
low end in terms of combustion efficiency (9). Typical
biomass cook stoves convert 6-20% of the fuel carbon
to toxic substances. What fuels actual cooking is only
18%, whereas 74% of the carbon is dissipated as waste
heat (10). Burning biomass fuels emits toxic fumes
into the air, and the content of these fumes will now be
described in detail.
4.1. Small solid particles
Particles with a diameter smaller than 10 m (PM10),
and particularly those with a diameter smaller than
2.5 m (PM2.5), can penetrate deeply into the lungs
and appear to have the greatest potential for damaging
health. Several studies have shown remarkable
consistency in the relationship between change in daily
ambient suspended particulate levels and subsequent
changes in mortality (11). The range of risk was found
to be 1.2-4.4% increased mortality per 10 mg/m
3
increase in concentration of respirable suspended
particles. The concentration distribution of indoor
particles less than 10 m (PM10) measured over 24
h in Indian households using solid fuels was over
2,000 g/m
3
compared to 30 g/m
3
in the US (11).
The determination of the concentration of suspended
particles offers the best indicator of health risk (12). A
simple Monte Carlo single-box model is presented as
a recent approach to examine the relationship between
emissions of pollutants from fuel as well as stove
combinations and the resulting Indoor Air Pollution
(IAP) concentrations (13). This model combines stove
emission rates with expected distributions of kitchen
volumes and air exchange rates in the context of a
developing country to produce a distribution of IAP
concentration estimates that can be used to predict if
IAP concentrations will meet air quality guidelines,
including those recommended by the WHO for
fine particulate matter (PM2.5) (14). The modeled
distributions of indoor PM2.5 concentration estimated
that only 4% of homes using fuel wood in a rocket-style
cook stove, even under ideal conditions, would meet
the WHO Interim-1 annual PM2.5 guideline of 35 mg/
m
3
. According to the model, the PM2.5 emissions that
would be required for even 50% of homes to meet this
guideline (0.055 g MJ-delivered-1) are lower than those
for an advanced gasifier fan stove, while emissions
levels akin to those of liquefied petroleum gas (0.018 g
MJ-delivered-1) would be required for 90% of homes to
meet the guideline. Although the predicted distribution
of PM concentrations (median-1,320 g/m
3
) from
inputs for traditional wood stoves was within the range
of reported values for India (108-3,522 g/m
3
), the
model likely overestimates IAP concentrations.
4.2. Carbon monoxide
An estimated 38 g, 17 g, 5 g, and 2 g/meal of carbon
monoxide is released during household cooking using
dung, crop residues, wood, and kerosene, respectively
(15). The short-term health effects of CO exposure
include dizziness, headaches, nausea, and feeling weak.
An association between long-term exposure to carbon
monoxide from cigarette smoke and heart disease and
fetal development has been noted (16).
4.3. Polyorganic and polyaromatic hydrocarbons
Polyaromatic hydrocarbons include a large class of
compounds released during the incomplete combustion
of organic matter (17). Benzopyrene is one of the most
important carcinogens in this group (18). In addition to
PAH, azo and amino compounds have also been found
to be potentially carcinogenic. A study by the National
Institute of Occupational Health showed that the
indoor levels of PAH (total) in air during use of dung,
wood, coal, kerosene, and LPG were 3.56, 2.01, 0.55,
0.23, and 0.13 g/m
3
, respectively (19). These PAHs
include fluorine, pyrene, chrysene, benzoanthracene,
benzofluoranthene, benzofluoranthene, benzopyrene,
dibenzanthracene, benzoperylene, and indenopyrene.
220
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BioScience Trends. 2012; 6(5):219-228. 221
it does differ significantly (p < 0.05) for cooks using
open outdoor kitchens as emissions are dispersed more
outdoors. Therefore cooks using an open outdoor
kitchen have less exposure than cooks using an
enclosed kitchen. Households with kitchens without
partitions have higher concentrations of particles in
living areas. Young children and the elderly often
occupy living areas and are exposed to higher levels
of smoke in unpartitioned indoor kitchens. Among
individuals not cooking in a household using solid
fuels, women who were not involved in cooking and
men with outdoor jobs had the lowest exposure, while
women who assisted with cooking and men staying at
home had the highest exposure. The level of exposure
does not appear to be significantly associated with
the length of cooking, the number of meals cooked,
outdoor area measurements, or the presence or absence
of chimneys (10,24).
6. Respiratory effects of biomass fuels
Many respiratory diseases have been found to be
associated with exposure to biomass fuels. The strength
of association varies for diseases like acute respiratory
infections (ALRI), chronic obstructive pulmonary
disease (COPD), lung cancer, pulmonary tuberculosis
(TB), asthma, and interstitial lung disease (ILD).
The evidence relates to this strength of association is
depicted in Table 1 (25). The relative risks shown in
the table are generally applicable since they are based
on the entire evidence base. The relative risks include
the results of formal meta-analyses with regard to
ALRI, COPD, and lung cancer (from exposure to coal
smoke). More recent studies including meta-analyses
of the available epidemiological evidence have been
conducted in India, as summarized in Table 2.
6.1. ALRI in children under 5 years of age
ALRI accounts for 13% of deaths and 11% of the
national burden of disease (6). One of the major
diseases associated with indoor air quality is ALRI. It
includes infections from a wide range of viruses and
bacteria but with similar symptoms and risk factors
(26). Many studies have found that various respiratory
symptoms (coughing, wheezing, etc.) are associated
with solid fuel smoke exposure. However, none have
provided sufficient evidence to calculate odds ratios.
A host of odd's ratios ranging from 1.9-2.7 have been
calculated (25). These ratios pertain to children with
ALRI younger than 5 years only. Other factors might
strongly influence the incidence of ALRI, such as
housing type, cooking location, and cultural practices
(27). Some of the studies in India have reported no
association between use of biomass fuels and ALRI in
children. In a case-controlled study of children under
five years of age in southern Kerala, India, children
All but the first three of these PAHs have been
classified as possible carcinogens.
4.4. Formaldehyde
The mean levels of formaldehyde emitted from cattle
dung (670 g/m
3
), wood (652 g/m
3
), coal (109 g/
m
3
), kerosene (112 g/m
3
), and LPG (68 g/m
3
) have
been calculated (20). In an epidemiological study
in the UK, significantly excess mortality from lung
cancer was observed in workers exposed to high levels
of formaldehyde (21). Formaldehyde is recognized
as an acute irritant and long-term exposure to it
can cause a reduction in vital capacity and chronic
bronchitis. It is known to form crosslinks with biologic
macromolecules. Inhaled formaldehyde forms DNA
and DNA-protein cross-links in the nasal respiratory
mucosa (22). Studies in workers occupationally
exposed to formaldehyde have consistently noted a
higher incidence of leukemia (23).
Biomass smoke has a pathological effect. The
toxic fumes released from a biomass stove contain
organic chemicals that are known mutagens, immune
system suppressants, severe irritants, blood poisons,
inflammatory agents, CNS depressants, cilia toxins,
endocrine disruptors, and neurotoxins. A number of
other chemicals released have been demonstrated to be
human carcinogens. Several toxic inorganic chemicals
are known to cause asphyxiation, stillbirth, infant
death, heart disease, and severe acute and chronic
lung disease. Many mechanisms of cell injury are still
unexplained.
5. Household composition and biomass smoke
exposure
The level of exposure to the toxic fumes from a
biomass stove varies widely with the house architecture
and household composition. Quantitative exposure
assessments have been conducted in various households
in different parts of India in order to determine
exposure-response relationships. The climatic and
cultural variations between northern and southern India
have influenced outcomes significantly. Cooking areas
in many Indian households tend to be poorly ventilated,
and about one-half of all households do not have a
separate kitchen. Most households lack a chimney
or other means of ventilation. One study conducted
in Porur, Chennai reported that 36% of households
use biomass fuels to cook in indoor kitchens without
partitions, 30% cook in a separate kitchen inside the
house, 19% cook in a separate kitchen outside the
house, and 16% cook in an outdoor kitchen (24). The
level of individual exposure to respirable particles in
biomass smoke does not significantly differ for cooks
using an indoor kitchen with or without partitions and
cooks using a separate kitchen outside the house but
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BioScience Trends. 2012; 6(5):219-228.
222
Table 1. Evidence relating to the strength of the association between biomass fuels and some common respiratory diseases
in developing countries
Evidence
Strong
a
Strong
a
Moderate-I
b
Strong
a
Moderate-I
b
Moderate-II
c
Moderate-II
c
Moderate-II
c
a
"Strong" indicates that the results of studies on household pollution in developing countries reveal a consistent, sizeable, plausible, and coherent
relationship, with supporting evidence from studies of outdoor air pollution, active and passive smoking, and laboratory animals
.
"Moderate"
indicates a relatively small number of suggestive findings from studies on household pollution in developing countries, and some evidence from
studies on outdoor air pollution, smoking, or laboratory animals indicating further more studies are required to strengthen the evidence base and
pinpoint risks. Moderate can be further classified as:
b
"Moderate-I" indicates an association between solid fuel use and a health outcome for
which there is strong evidence for specific age and sex groups;
c
"Moderate-II" indicates that there is as yet no strong evidence. Note: Studies
conducted in India are shown in bold. Adapted from Desai MA, Mehta S, Smith KR. WHO protection of the human environment, Geneva, 2004
(25) and Smith KR. National burden of disease in India from indoor air pollution. Proc Natl Acad Sci. 2000 (6).
Health outcome
ALRI
COPD
COPD
Lung Cancer (Coal smoke exposure)
Lung Cancer (Coal smoke exposure)
Lung Cancer (Biomass smoke exposure)
Asthma
Tuberculosis
Group
(age) (ys)
Children < 5
Women 30
Men 30
Women 30
Men 30
Women 30
Children 5-14
All 15
All 15
Relative
risk
2.3
3.2
1.8
1.9
1.5
1.5
1.6
1.2
1.5
95% CI
1.9-2.7
2.3-4.8
1.0-3.2
1.1-3.5
1.0-2.5
1.0-2.1
1.0-2.5
1.0-1.5
1.0-2.4
Studies
Campbell, Armsrong & Bypass (1989)
Armstrong & Campbell (1991)
Cerquiero (1990)
Collings, Sithole & Martin (1990)
De Francisco (1993)
Ezzati & Kammen (2001)
Johnson & Aderele (1992)
Kossove (1982)
Morris (1990)
Mtango (1992)
O'Dempsey (1996)
Pandey (1989)
Robin (1996)
Shah (1994)
Victora (1994)
Albalak, Frisancho & Keeler (1999)
Behera, Dash & Yadav (1991)
Dennis (1996)
Dossing & Khan (1994)
Dutt (1996)
Gupta & Mathur (1997)
Malik (1985)
Menezes, Victora & Rigatto (1994)
Pandey (1984)
Perez-Padilla (1996)
Qureshi (1994)
Dai (1996)
Du (1988)
Du (1996)
Gao (1987)
Huang (1999)
Ko (1997)
Lei (1996)
Liu, He & Chapman (1991)
Liu (1993)
J. Liu & H. Hu (Unpublished data)
Luo (1996)
Shen (1996)
Sobue (1990)
Wang, Zhou & Shi (1996)
Wu (1985)
Wu-Williams (1990)
Wu (1999)
Xu (1996)
Yang, Jiang & Wang (1988)
Azizi, Zulkifi & Kasim (1995)
Mohamed (1995)
Xu, Niu & Christian (1996)
Gupta & Mathur (1997)
Mishra, Retherford & Smith (1999)
Perez-Padilla (1996)
Perez-Padilla (2001)
Location
Gambia
Gambia
Argentina
Zimbabwe
Gambia
Kenya
Nigeria
S. Africa
USA
Tanzania
Gambia
Nepal
USA
India
Brazil
Bolivia
India
Colombia
Saudi Arabia
India
India
India
Brazil
Nepal
Mexico
India
China
China
China
China
China
Taiwan
China
China
China
China
China
China
Japan
China
USA
China
China
China
China
Malaysia
Kenya
China
India
India
Mexico
Mexico
Ref.
(45)
(46)
(47)
(48)
(49)
(50)
(51)
(52)
(53)
(54)
(55)
(56)
(57)
(28)
(58)
(59)
(60)
(61)
(62)
(63)
(30)
(64)
(65)
(66)
(67)
(68)
(69)
(70)
(71)
(72)
(73)
(74)
(75)
(76)
(77)
(78)
(79)
(80)
(81)
(82)
(83)
(84)
(85)
(86)
(87)
(88)
(89)
(90)
(30)
(98)
(67)
(91)
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BioScience Trends. 2012; 6(5):219-228. 223
with severe pneumonia (meeting WHO criteria) were
compared to those with non-severe ALRI seen as
outpatients. According to the study, cooking fuel was
not a major risk factor for severe ALRI (28). In a cross-
sectional study involving 642 infants dwelling in urban
slums of Delhi where wood and kerosene were used,
Sharma et al. found no significant difference in the
prevalence of ALRI infections and the type of fuel (27).
6.2. COPD
COPD accounts for 1.5% of deaths and represents 0.9%
of the national burden of disease in India (6). Both men
and women have similar rates of incidence of chronic
cor pulmonale. This is despite the fact that only 10%
of women are smokers compared to 75% of men.
Another point to note is that chronic cor pulmonale
occurs 10-15 years earlier in women than in men (29).
Various Indian studies have calculated a relative risk of
2-4 for biomass fuel exposure (6). Despite the progress
made in highlighting the association between biomass
fuel exposure and COPD, many problems still exist.
Smoking is an important confounding variable for
COPD and particularly so when men are included in
the analyses. Another major confounding factor is age.
The risk of COPD increases with age and many age-
matched studies have provided insufficient quantitative
evidence to develop an odds ratio. The overall risk of
COPD in women exposed to biomass fuel has been
estimated as 3.2 (95% CI 2.3-4.8) (25). There is much
less evidence available about the impact on men, but
the risk seems to be lower with an odds ratio (OR) of 1.8
(95% CI 1.0-3.2). This may be attributed to the lower
exposure of men to biomass fumes (30).
6.3. Lung cancer
Lung cancer in women is an amply demonstrated
outcome of cooking with open coal stoves in China
(31). Indian women generally have low lung cancer
rates (32). This may be attributed to the minimal use of
coal for cooking in Indian households. Nevertheless, a
few studies in India have suggested an association with
lung cancer even after adjusting for active and passive
smoking. An odds ratio of 3.59 (95% CI 1.07-11.97)
has been calculated (33). In conclusion, there is a
general lack of epidemiological evidence associating
lung cancer with biomass fuel exposure. The few cases
reported have been linked to exposure to coal fires (34).
6.4. TB
TB is a major public health problem in India. Out of the
9.4 million new cases recorded globally, 1.98 million
are reported from India (35). An estimated 276,000
deaths occur annually due to TB in India. There is a
Table 2. Major Indian studies depicting the association between current solid fuel use relative to cleaner burning fuel or
electricity and the risk of common respiratory diseases
Ref.
(30)
(98)
(93)
(102)
(36)
(95)
(94)
(98)
(96)
(103)
(99)
(33)
(34)
(100)
(101)
(68)
(97)
Odd's ratio/Incidence
risk ratio (95% CI)
2.54 (1.07-6.04)
2.58 (1.98-3.37))
3.26 (1.25-8.46)
0.22 (0.12-0.41)
2.9 (1.8-4.7)
0.60 (0.22-1.63)
2.33 (1.18-4.59)
1.58 (1.28-1.95)
1.78 (1.45-2.18)
1.33 (1.02-1.73)
1.52 (0.33-6.98)
3.59 (1.07-11.97)
3.76 (1.64-8.63)
2.15 (1.61-2.89)
3.04 (2.15-4.31)
2.10 (1.50-2.94)
2.80 (1.85-4.0)
Outcome
Clinical pulmonary
Self-reported
Clinical Pulmonary
Clinical Pulmonary
Clinical pulmonary
Clinical pulmonary
Clinical pulmonary
Self-reported symptoms
24 studies for calculation of OR
Clinical symptoms and estimation
of the incidence risk ratio among
children from households using
biomass fuels relative to cleaner
fuels
Clinical, radiological, and his-
topathological assessment
Clinical, radiological, and his-
topathological assessment
Clinical, radiological, and his-
topathological assessment
25 studies for estimation of OR
Clinical assessment
Clinical assessment
12 studies for estimation of OR
Study type
Case-control India
Cross-sectional: India (National
Family Health Survey)
Case-control India
Case-control India
Case-control India
Case- control India
Case-control India
Cross-sectional survey
Meta-analysis
Longitudinal cohort
Case- control India
Case-control India
Case-control India
Meta-analysis
Descriptive study
Case-control India
Meta-analysis
Authors
Gupta et al. (1997)
Mishra et al. (1999)
Shetty et al. (2006)
Mageshwari U et al. (2008)
Kolappan et al. (2009)
Behera D et al. (2010)
Lakshmi et al. (2012)
Mishra et al. (2005)
Dherani et al. (2008)
Ramaswamy P et al. (2011)
Gupta D et al. (2001)
Behera D et al. (2005)
Sapkota A et al. (2008)
Hosgood HD et al. (2011)
Behera D et al. (1991)
Qureshi et al. (1994)
Kurmi OP et al. (2010)
Respiratory disease
Tuberculosis
ALRI
Lung cancer
COPD
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BioScience Trends. 2012; 6(5):219-228.
strong association between the use of biomass fuel and
pulmonary TB. A high risk of pulmonary TB exists in
individuals using wood and cow dung cake as cooking
fuel (36). Lowered immunodefense mechanisms of the
lung may why the disease develops. Biomass fuel poses
a higher risk (969/100,000) of TB compared to cleaner
fuels (378/100,000). Fifty-one percent of active TB in
individuals over 20 is believed to be attributed to smoke
from cooking with biomass fuels (37).
A study in Nepal implicated the use of kerosene
stoves and wick lamps in the development of TB.
Compared to use of a cleaner fuel like LPG or biogas,
the adjusted OR for using a biomass fuel stove was
1.21 (95% CI 0.48-3.05). A kerosene fuel stove had an
OR of 3.36 (95% CI 1.01-11.22). The OR of biomass
fuel for heating was 3.45 (95% CI 1.44-8.27). Kerosene
lamps used for lighting had an OR of 9.43 (95% CI
1.45-61.32). This study further found that use of indoor
biomass fuel for heating purposes is associated with TB
in women (38). This is supported by a recent study in
India (94). Given the prevalence of TB in India and its
likeliness to increase with HIV, these findings need to
be followed up with more detailed studies.
6.5. Pneumoconiosis and ILD
Pneumoconiosis has been reported from Ladakh, a
hilly region in northernmost India (39). This place
is completely devoid of industries or mines, and yet
cases of a disease resembling miner's pneumoconiosis
have been reported. Another factor for this respiratory
morbidity is exposure to dust from dust storms. In the
spring, dust storms blanket villages in fine dust. The
practice of not allowing wood to burn quickly and
allowing it to smoulder to conserve fuel adds to the high
level of respirable particles indoors. Low oxygen levels
or some other factor associated with a high altitude
may contribute to pneumoconiosis because miners
working at high altitudes are more prone to develop
pneumoconiosis than their counterparts who are
exposed to the same levels of dust and work in mines
at normal altitudes (40). Biomass fuel exposure has not
been proven to cause pneumoconiosis (39). Although a
few case reports have similarly linked ILD and biomass
fuel exposure, the validity of the association is still
debatable (41).
7. Toxicological evidence of the strength of the
association between biomass fuels and respiratory
diseases
Toxicological studies are quite useful to study the
effects of air pollutants on humans but cannot be
conducted directly because of limitations such as
societal concerns, ethical and legal issues, and cost.
Therefore, predictive health assessments of inhaled
pollutants need to include information gained from
animal exposure studies and, in some cases, in vitro/
ex vivo assay systems in order to overcome these
limitations. These animal studies contribute to a
better understanding of the possible mechanisms(s)
by which smoke, and its associated PM, may act to
bring about increased pulmonary morbidity in exposed
individuals and also have the potential to help uncover
information concerning the mechanisms of toxicity
and relative toxicity of different mixtures and sources.
Few toxicological studies in India have indicated
that exposure to smoke results in significant impacts
on the respiratory immune system and can produce
long-term or permanent lesions in lung tissues at
high doses. These effects seem to be most strongly
associated with the particle phase. Lal et al. examined
the hematological and histopathologic responses of
rats exposed repeatedly to smoke generated from the
combustion of wood dust and they found that the
rats had cell desquamation, pulmonary edema, and
perivascular infiltration of neutrophils upon acute
exposure and emphysematous alveolar destruction
as well as eosinophilia upon chronic exposure (42).
Bhattacharyya et al. examined the effects of pinewood
smoke exposure on rabbit tracheal explants for 20
minutes and found degeneration of the mucociliary
epithelial sheath although shorter exposure to smoke
of 10 minutes resulted in retained tissue integrity
but altered epithelial morphology (43). Thus, these
toxicological studies indicate biological plausibility of
the epidemiologic evidence suggesting that exposure
to smoke emissions adversely affects human health.
Clearly, short-term inhalation of smoke appears to
compromise pulmonary immune defense mechanisms
that are vital to maintaining host resistance against
pulmonary infections. These studies lend support
to the notion that inhaled smoke contributes to the
increased incidence of infectious respiratory disease
reported in children living in developing nations and/
or near homes heated by wood burning devices (44).
Data are currently insufficient to reliably distinguish
the toxicological effects of different types of biomass
smoke. More work in this area is needed to better
understand the mechanisms by which adverse effects
observed in exposed individuals might occur.
8. Conclusion
In conclusion, biomass fuel exposure contributes
substantially to the burden of disease in India. Many
studies in this vein have discovered significant
associations with diseases like ALRI and COPD. More
evidence is needed to establish the association between
solid fuel smoke and other diseases. Implementing
strategies to reduce or eliminate exposure is very
challenging because it must consider the level of
individual exposure as well as cultural and economic
aspects at the individual and local levels, including the
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level of development, resources, technical capacity,
domestic energy needs, the sustainability of the
sources of energy considered, and protection of the
environment. Substantial improvement can be brought
about by health education and cultural changes,
modification of stove design, and switching over to
cleaner fuels or other high-efficiency low-emission
fuels for cooking. Physicians and health administrators
should have a heightened awareness of the health
effects of solid fuel smoke inhalation as this may
spur research and preventive measures and facilitate
the diagnosis and treatment of future patients. Hopes
are that future studies will examine the morbidity
associated with biomass exposure and seek to prevent
it. This is a pressing issue given the great risk posed by
solid fuels in rural India.
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(Received August 1, 2012; Revised October 6, 2012;
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