The effects of smokeless cookstoves on peak expiratory flow rates in rural Honduras
Journal of Public Health |
The effects of smokeless cookstoves on peak expiratory flow rates in rural Honduras
W.P. Rennert 0
R.M. Porras Blanco 0
G.B. Muniz 0
0 Department of Pediatrics, Georgetown University , 4200 Wisconsin Ave, NW, Washington, DC 20016 , USA
A B S T R AC T Background The use of biomass fuel for cooking in traditional cookstove designs negatively affects respiratory health of communities in developing countries. Indoor pollution affects particularly women and children, who are participating in food preparation. The effects of smokeless cookstove designs on indoor pollution are well documented, but few studies exist to assess the effects of improved stove designs on the respiratory health of community members. Methods This study uses peak expiratory flow rate (PEFR) measurements in a before-and-after format to assess respiratory function of inhabitants of all 30 houses of Buenas Noches in central Honduras. PEFRs are measured before and 6 months after the installation of Justa stoves in people's homes. Health behaviors, respiratory symptoms and fire wood use are evaluated in a door-to-door survey format. Results A total of 137 eligible women and children between 6 and 14 years participated in the study. PEFR improved by 9.9 - 18.5% (P , 0.001) depending on the participants' exposure to indoor pollution. Health complaints like cough and behaviors like clinic visits did not change with the introduction of smokeless cookstove technology. Conclusions Smokeless stoves improve respiratory health in an environment of high levels of indoor pollution.
air pollution; children; communities
Half the world’s population, virtually all of them in developing
countries rely on solid biomass fuels like wood, crop residues,
dung and charcoal for cooking and heating.1 – 3 Incomplete
combustion of solid fuels from poorly ventilated traditional
stoves or open fire pits lead to particulate matter (PM) and
carbon monoxide (CO) emissions 10 – 20 times greater than
those recommended by WHO air quality standards.4 PM10
( particular matter particles of ,10-mm aerodynamic
diameter) and even more so PM2.5 (,2.5-mm aerodynamic
diameter) are easily inhaled and reach the smallest bronchioles
deep in the lung parenchyma.5 – 9
Exposure to indoor pollution and high PM10 and PM2.5
levels have been associated with low birth weight and
stillbirths in newborns,10 – 12 stunting, asthma and acute
respiratory infections in children,13 – 17, and chronic obstructive
pulmonary disease and cancer in women.9,17 – 20 As many as
2 million deaths annually can be attributed to the effects of
solid biomass fuel use.20 – 22 ‘Hut Lung’, an interstitial lung
disease marked by fibrosis, inflammation and deposits of
dusts and carbon in the lungs, has been described as a
specific disease entity in women exposed to chronic indoor
Outdoor relocation of cooking, partitioning of kitchens
from living spaces, improved ventilation of kitchen areas and
the introduction of improved cookstoves have all been
suggested to reduce exposure to indoor pollution.9,13,25,26 A
variety of designs for improved, ventilated cookstoves have
been introduced in a number of countries to reduce indoor
pollution as well as the amount of solid biomass fuel used for
food preparation.26 – 29 Field trials using improved cookstoves
have been able to show reductions in PM10, PM2.5 as well as
CO emissions, but few studies exist demonstrating
measurable concomitant effects on health outcomes.13,30 – 34 Most
studies rely on self-reported quality-of-life improvements
documented through community surveys or health behavior
The effects of indoor pollution on lung function have been
reliably related to reduction in forced vital capacity, forced
expiratory volume in 1 s (FEV1) and peak expiratory flow
rate (PEFR)35 – 39 among exposed women and children. Few
studies exist, however, using quantifiable measures of lung
function to assess the potentially beneficial effects of reduced
indoor pollution on respiratory health following the
introduction of improved cookstove designs. We conducted a clinical
trial in a rural community in central Honduras using the
introduction of a locally available improved cookstove (Justa stove)
as the intervention and measuring PEFR in women and
children in a ‘before and after’ study format.30,32
All 30 households of the community of Buenas Noches in the
mountainous region around Comayagua in central Honduras
participated in the study. The area is inaccessible by road,
none of the houses have electricity and all households use
simple wood-burning adobe cookstoves for food preparation.
Cooking and living spaces are not separated in any of the
houses, but sleeping quarters tend to be divided off with
simple curtains. Community members depend on subsistence
farming and provide manual labor to coffee farms in the
All households agreed to replace their traditional adobe
stoves with Justa stoves that provide an improved combustion
chamber and a chimney. The introduction of Justa stoves had
led to significant reductions of CO, PM10 and PM2.5 levels in
a comparable community in the same area of Honduras in a
previous field trial.31 All adult household members received
individual instructions on how to operate, maintain and clean
their new stove. Data were obtained in July 2013 and March
2014, before and after the rainy season, when the temperatures
were warm, the humidity low and the precipitation modest.
Oral consent was obtained from household members in a
standardized Spanish format that had been approved by the IRB of
PEFR measurements were taken from nonsmoking women
aged 15 or older and children aged 6 – 14 before and 8 months
after the installation of Justa stoves. PEFRs were measured using
an ASSESS Standard or Low Range Peak Flow Meter in standing
position. Results were related to the participants’ height
using the formula: PEFR (l/min) ¼ [height (cm) 2 80] 5
and compared with US normograms.40 Results were recorded
as percentage of US standards for healthy individuals of
the same height in order to control for the growth of children
between the assessment intervals.41 The highest of three
measurements were recorded. Measurements were taken on
all participants by the same team member. A different team
member recorded the results not disclosing prior PEFR
values to the team member administering the test.
The number of rooms and windows were recorded, and
household members were identified who participated in food
preparation. Similarly, respiratory health symptoms and clinic
visits were recorded for adults and children. The study was
approved by the Georgetown University IRB and was
supported by a grant from the Georgetown University
Paired and unpaired t-tests were used to compare
continuous variables such as PEFR, whereas Fisher’s Exact tests were
used to compare categorical variables such as the presence or
absence of cough or asthma. GraphPad InStat 3 software
(GraphPad Software, Inc., La Jolla, CA, USA) was used to
compute the data.
A total of 230 people lived in the 30 households under
investigation at a rate of 7.6 family members per household. Fifty
nonsmoking women aged 15 or older agreed to have their
PEFR measured, 41 before, 27 after and 21 before and after
the installation of Justa stoves. Eighty-seven children (43
females and 44 males) between 6 and 14 years of age also had
their peak flows measured before and/or after the installation
of improved cookstoves in their homes. Fifty-nine of them
had their PEFR tested at both data collection points
(Table 1). Children below the age of 6 were unable to
cooperate with the PEFR measurements. Men of 15 years or older
were excluded as they spend most of their time outside the
homestead. After the exclusion of men and children younger
than 6 years, 137 subjects remained in the study, 80 of whom
(58.4%) could be followed in a strict before/after format,
where each subject functioned as their own control.
Houses had on average 2.2 rooms [standard deviation (SD)
0.9], typically separating a sleeping area from a cooking/living
area with a curtain. Twenty-one kitchens had simple chimneys,
whereas 15 kitchens had a small window. Four houses had
neither a chimney nor a window in their kitchen. Women
engaged in cooking activities reported the use of 16 (SD 4.3)
branches of fire wood per day for cooking before the
installation of Justa stoves.
In each household, women were asked whether they or any
of their family members had been coughing during the
aMen and children younger than 6 years were excluded from the study.
previous month, whether they had been visiting the local clinic
for respiratory problems and whether any family member had
been diagnosed with asthma. No differences could be found
for any of these variables comparing before and after Justa
stove installation assessment points (Table 2).
Peak expiratory flow rates were recorded as percentage of
US standards for healthy individuals of the same height in
order to control for the growth of children between the
assessment intervals.41 Overall villagers’ PEFR improved from
88.2% of US norm standards to 102.9% (P , 0.001; CI 8.7 –
20.8) after the installation of smokeless stoves in their homes.
Women of 15 years or older improved from 75.5 to 94.0%
(P , 0.001; CI 9.4 – 27.6), whereas children of 6 – 14 years of
age improved from 94.3 to 106.8% (P , 0.001; CI 5.3 – 19.8).
These differences were maintained when looking only at
participants who had PEFR measurements at both data
collection points in the study using a paired t-test format (Table 3).
All female study participants aged 15 or older engaged in
food preparation, whereas none of the male participants spent
significant time in the kitchen. A comparison between
participants who were involved with food preparation and those who
were not was possible for female children between the ages of 6
and 14. Sixteen of them were involved with cooking (10 of
them had PEFR measurements before and after the installation
of Justa stoves in their homes), whereas 13 were not (9 of them
had PEFR measurements before and after the installation of
Justa stoves in their homes). Female children who spent
significant time in the kitchen had lower PEFR than their
noncooking peers (83.0 versus 103.0%) before they received new
cookstoves, improving to normal US standards (99.1 versus
110.3%) after the installation of the Justa stoves (Figure 1).
All children—male and female—not involved with food
preparation had PEFR percentages of .90% of US
standards before the installation of smokeless stoves in their
homes. While they did benefit from living in a smokeless
Table 2 Clinical health indicators reported by senior woman for each
household before and after the installation of Justa stoves
P-value (relative risk)
Clinical health indicators and behaviors
Cough (adults) 11 18
Cough (children) 17 12
Clinic visits (adults) 3 26
Clinic visits (children) 6 23
Asthma (adults) 0 29
Asthma (children) 4 25
environment after Justa stove installation documented by an
increase in PEFR, the real benefit of the smokeless stove
technology was enjoyed by participants, who spent significant
time in their kitchens engaging in food preparation.
Main finding of the study
Women and children engaged in food preparation
demonstrated the lowest PEFR values before and the largest
improvement after the introduction of smokeless cookstoves,
indicating that indoor pollution related to the use of biomass
fuel adversely affects respiratory health starting in childhood
and persisting throughout adulthood. The effects seem to be
reversible as adults and children had similar ranges of
improvement after the intervention. Children, who did not
participate in cooking activities, also showed improvement albeit
to a lesser degree in their PEFR values after the introduction
of smokeless cookstoves, indicating that the use of biomass
PEFR before (n)
PEFR after (n)
Mean difference (%)
P-value (confidence interval)
Peak expiratory flow rates before and after Justa stove installation
Women and children 88.2% (126)
Women 15 years 75.5% (41)
Women paireda 78.0% (21)
Children 6– 14 years 94.2% (85)
Children paireda 95.1% (59)
Females 6– 14 years 87.8% (42)
Females 6– 14 paireda 91.1% (27)
Males 6– 14 years 100.7% (43)
Males 6– 14 paireda 98.5% (32)
aSubjects who had their PEFR tested before and after stove installation.
PEFR before Justa stove
PEFR after Justa stove
Cooking (p < 0.05)
Not cooking (p > 0.05)
Fig. 1 PEFR percentage of US standards for girls aged 6 to 14 involved (left,
n ¼ 10) and not involved (right, n ¼ 9) with food preparation before and
after Justa stove installation.
fuel for cooking affects the indoor air quality beyond the
actual cooking process.
None of the study participants indicated a change in
subjective health status or behavior such as cough or clinic visits.
Symptoms of cough may relate to other diseases like viral
infections that are unrelated to indoor pollution, whereas
visits to health providers may be hard to interpret in an
environment where health workers are scarce, clinic visits
expensive and health facilities poorly accessible. One may have to
question the validity of health behavior surveys and subjective
quality-of-life reports as an outcome measure for health
interventions such as the introduction of smokeless stove
technology under such circumstances.26,27,30
What is already known on this topic
Indoor pollution from incomplete combustion of solid biomass
fuels is a well-known health hazard across the developing
world.5,8,9,42,43 Pneumonia, asthma, chronic restrictive lung
disease and cancer are related respiratory health issues.13 – 20,23 – 44
Improved cookstove designs have been shown to reduce
pollution levels, fuel use and cost.25 – 29,45
PEFR measurements have been used reliably to measure
the effects of indoor pollution on lung function.36 – 38 In this
study, PEFR measurements are used to establish the potential
benefits of smokeless cookstove technology on respiratory
health. Using US reference standards for PEFR
measurements in a developing world context did not introduce bias,
as we were less interested in the absolute PEFR values of
study participants, but rather in the change of PEFR values
after the introduction of smokeless cookstoves. On the other
hand, the proximity of participants’ PEFR values to US
standards particularly after the introduction of smokeless
cookstoves suggests a good quality of respiratory effort on the part
of the study participants.
What this study adds
Much is known about the effects of smokeless cookstove
technology on indoor air quality, but few studies have
been conducted to measure positive health impacts of the
new technology beyond quality-of-life surveys.26,27,30 – 34
This study correlates the introduction of smokeless stove
technology to improvements of respiratory health with the
help of PEFR measurements in individuals exposed to
indoor pollution. We did not confirm participants’
subjective health benefits, while adding quantitative
information about improved lung function. We believe that
subjective health assessments are affected by additional
variables such as intercurrent diseases, socioeconomic
influences, access to available health services and health
Limitations of the study
PEFR measurements have shown to reliably assess lung
function in environments of indoor pollution,36 – 39 but they are
also to some extent user and effort dependent. We tried to
account for this limitation by creating a testing environment
that is as standardized as possible, using the same team
member to administer the test to all participants, a different
team member to record the results and the same instructions
given to each participant before the test. The proximity of test
results to US norm standards among participants with lower
exposure to indoor pollution confirms the quality of the
respiratory efforts on the part of the study participants.
Another potential shortcoming of the study is the fact that
only 80 of 137 (58.4%) participants were followed in a strict
before/after format, where each participant functions as their
own control. Nevertheless, the results of subjects who
participated at only one of the two PEFR measuring points were
identical to those who participated in both.
The study was conducted in the months of July and March.
Although it may have been preferable to choose the same study
month for both PEFR data collection points, the climatic
conditions of temperature, humidity and precipitation were similar
at the two data collection points.
The use of biomass fuel for cooking in traditional
woodburning cookstove designs compromises the respiratory
health of communities in the developing world. Particularly,
women and children engaged in food preparation are affected.
We documented negative respiratory health effects of indoor
pollution beginning in childhood and continuing through
adulthood by PEFR measurements. The introduction of smokeless
cookstove technology improved PEFR in both children and
adults, indicating that adverse health effects relating to indoor
pollution are potentially reversible.
THE EFFECT S OF SMOKELESS COOKSTOVES
1 2 3 4 WHO, UNDP. The Energy Access Situation in Developing Countries: A Review Focusing on the Least Developed Countries and Sub-Saharan Africa .
New York, NY: United Nations Development Program , 2012 .
Kaplan C. Indoor air pollution from unprocessed solid fuels in developing countries . Rev Environ Health 2010 ; 25 ( 3 ): 221 - 42 .
Bruce N , Perez-Padilla R , Albalak R. Indoor air pollution in developing countries: a major environmental and public health challenge . Bull World Health Organ 2000 ; 78 ( 9 ): 1078 - 92 .
WHO European Center for Environmental Health . WHO Guidelines for Indoor Air Quality: Selected Pollutants . Copenhagen, Denmark: WHO Regional Office for Europe , 2010 .
5 Sood A. Indoor fuel exposure and the lung in both developing and developed countries: an update . Clin Chest Med 2012 ; 33 : 649 - 65 .
Massey D , Masih J , Kulshrestha A et al. Indoor/outdoor relationship of fine particles less than 2.5 mm (PM 2.5) in residential homes locations in central India region . Build Environ . 2009 ; 44 : 2037 - 45 .
7 Sallsten G , Gustafson P , Johansson L et al. Experimental wood smoke exposure in humans . Inhal Toxicol 2006 ; 18 : 855 - 64 .
Zhang J , Smith KR. Indoor air pollution: a global health concern . Br Med Bull 2003 ; 68 : 209 - 25 .
Kodgule R , Salvi S. Exposure to biomass smoke as a cause for airway disease in women and children . Curr Opin Allergy Clin Immunol 2012 ; 12 : 82 - 90 .
10 Pope DP , Mishra V , Thompson L et al. Risk of low birth weight and stillbirth associated with indoor air pollution from solid fuel use in developing countries . Epidemiol Rev 2010 ; 32 : 70 - 81 .
11 Boy E , Bruce N , Delgado H. Birth weight and exposure to kitchen wood smoke during pregnancy in rural Guatemala . Environ Health Perspect 2002 ; 110 ( 1 ): 109 - 14 .
12 Thompson LM , Bruce N , Eskenazi B et al. Impact of reduced maternal exposures to wood smoke from an introduced chimney stove on newborn birth weight in rural Guatemala . Environ Health Perspect 2011 ; 119 ( 10 ): 1489 - 94 .
13 Smith KR , McCracken JP , Weber MW et al. Effect of reduction in household air pollution on childhood pneumonia in Guatemala (RESPIRE): a randomized controlled trial . Lancet 2011 ; 378 : 1717 - 26 .
14 Breysse PN , Diette GB , Matsui EC et al. Indoor air pollution and asthma in children . Proc Am Thorac Soc 2010 ; 7 : 102 - 6 .
15 Dherani M , Pope D , Mascarenhas M et al. Indoor air pollution from unprocessed solid fuel use and pneumonia risk in children aged under five years: a systemic review and meta-analysis . Bull Wold Health Organ 2008 ; 86 ( 5 ): 390 - 8 .
16 Bruce NG , Dherani MK , Das JK et al. Control of household air pollution for child survival: estimates for intervention impacts . BMC Public Health 2013 ; 13 (suppl 3): S8 .
17 Perez-Padilla R , Schilman A , Riojas-Rodriguez H. Respiratory health effects of indoor air pollution . Int J Tuberc Lung Dis 2010 ; 14 ( 9 ): 1079 - 86 .
18 Torres-Duque C , Maldonado D , Perez-Padilla R et al. Biomass fuels and respiratory diseases: a review of the evidence . Proc Am Thorac Soc 2008 ; 5 ( 5 ): 577 - 90 .
19 Diette GB , Accinelli RA , Balmes JR et al. Obstructive lung disease and exposure to burning biomass fuel in the indoor environment . Global Heart 2012 ; 7 ( 3 ): 265 - 70 .
20 Fullerton DG , Bruce N , Gordon SB . Indoor air pollution from biomass fuel smoke is a major health concern in the developing world . Trans R Soc Trop Med Hyg 2008 ; 102 : 843 - 51 .
21 World Health Organization. Global Health Risks, Mortality and Burden of Disease Attributable to Selected Major Risks . Geneva, Switzerland: WHO, 2009 .
22 Prasad R , Singh A , Garg R et al. Biomass fuel exposure and respiratory diseases in India . BioSci Trends 2012 ; 6 ( 5 ): 219 - 28 .
23 Gold JA , Jagirdar J , Hay JG et al. Hut lung: a domestically acquired particulate lung disease . Medicine 2000 ; 79 : 310 - 7 .
24 Churg A , Myers J , Suarez T et al. Airway-centered interstitial fibrosis: a distinct form of aggressive diffuses lung disease . Am J Surg Path 2004 ; 28 : 62 - 8 .
25 Balakrishnan K , Sankar S , Parikh J et al. Daily average exposures to respirable particulate matter from combustion of biomass fuels in rural households of southern India . Environ Health Perspect 2002 ; 110 : 1069 - 75 .
26 Alexander D , Callihan Linnes J , Bolton S et al. Ventilated cookstoves associated with improvements in respiratory health-related quality of life in rural Bolivia . J Public Health 2013 ; 36 : 460 - 466 .
27 Smith KR. Indoor air pollution in developing countries: recommendations for research . Indoor Air 2002 ; 12 : 198 - 207 .
28 Nazmul Alam SM , Chowdhury SJ , Begum A et al. Effect of improved earthen stoves: improving health for rural communities in Bangladesh . Energy Sustain Develop 2006 ; 10 ( 3 ): 46 - 53 .
29 Jetter JJ , Kariher P. Solid fuel household cook stoves: characterization of performance and emissions . Biomass Bioenergy 2009 ; 33 : 294 - 305 .
30 Klasen E , Miranda JJ , Khatry S et al. Feasibility intervention trial of two types of improved cookstoves in three resource-limited settings: study protocol for a randomized controlled trial . Trials 2013 ; 14 :327. http://www.trialsjournal.com/content/14/1/327: (28 October 2014 , date last accessed).
31 Clark ML , Reynolds SJ , Burch JB et al. Indoor air pollution, cookstove quality, and housing characteristics in two Honduran communities . Environ Res 2010 ; 110 : 12 - 8 .
32 Edwards R , Hubbard A , Khalakdina A et al. Design considerations for field studies of changes in indoor air pollution due to improved stoves . Energy Sustain Develop 2007 ; 11 ( 2 ): 71 - 81 .
33 Begum BA , Paul SK , Hossain MD et al. Indoor air pollution from particulate matter emissions in different households in rural areas of Bangladesh . Build Environ 2009 ; 44 : 898 - 903 .
34 Granderson J , Sandhu JS , Vasquez D et al. Fuel use and design analysis of improved woodburning cookstoves in the Guatemalan Highlands . Biomass Bioenergy 2009 ; 33 : 306 - 15 .
35 Rinne ST , Rodas EJ , Bender BS et al. Relationship of pulmonary function among women and children to indoor air pollution from biomass use in rural Ecuador . Respir Med 2006 ; 100 : 1208 - 15 .
36 Wiwatanadate P , Liwsrisakun C. Acute effects of air pollution on peak expiratory flow rates and symptoms among asthmatic patients in Chiang Mai , Thailand. Int J Hyg Environ Health 2011 ; 214 : 251 - 7 .
37 Lankarani NB , Kreis I , Griffiths DA . Air pollution effects on peak expiratory flow rate in children . Iran J Allergy Asthma Immunal 2010 ; 9 ( 2 ): 117 - 26 .
38 Sukhsohale ND , Narlawar UW , Phatak MS et al. Effect of indoor air pollution during cooking on peak expiratory flow rate and its association with exposure index in rural women . Indian J Physiol Pharmacol 2013 ; 57 ( 2 ): 184 - 8 .
39 Kumar R , Nagar JK , Kumar H et al. Indoor air pollution and respiratory function of children in Ashok Vihar, Delhi: an exposureresponse study . Asia Pac J Public Health 2008 ; 20 ( 1 ): 36 - 48 .
40 Hankinson JL , Odencrantz JR , Fedan KB . Spirometric reference values from a sample of the general US population . Am J Respir Crit Care Med 1999 ; 159 ( 1 ): 179 .
41 Voter KZ . Diagnostic tests of lung function . Pediatr Rev 1996 ; 17 ( 2 ): 53 - 63 .
42 Balakrishnan K , Ramaswamy P , Sambandam S et al. Air pollution from household solid fuel combustion in India: an overview of exposure and health related information to inform health research priorities . Global Health Action 2011 ; 4 : 5638 .
43 Zhang J , Smith KR. Household air pollution from coal and biomass fuels in China: measurements, health impacts, and interventions . Environ Health Perspect 2007 ; 115 ( 6 ): 848 - 55 .
44 Smith KR , Samet JM , Romieu I et al. Indoor air pollution in developing countries and acute lower respiratory infections in children . Thorax 2000 ; 55 : 518 - 32 .
45 Hutton G , Rehfuess E , Tediosi F. Evaluation of the costs and benefits of interventions to reduce indoor air pollution . Energy Sustai Develop 2007 ; 11 ( 4 ): 34 - 43 .
46 Vonneilich N , Jockel KH , Erbel R et al. The mediating effect of social relationships on the association between socioeconomic status and subjective health-results from the Heinz Nixdorf Recall cohort study . BMC Public Health 2012 ; 12 :285. http://www.biomedcentral. com/1471-2458/12/285.