The effects of smokeless cookstoves on peak expiratory flow rates in rural Honduras

Journal of Public Health, Aug 2015

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.

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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 Background 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 pollution.23,24 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 questionnaires.26,27,30 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 Methods 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 region. 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 Georgetown University. 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 Environment Initiative. 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. Results 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 PEFR 1þ2 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. Discussion 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 literacy levels.46 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 . 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W.P. Rennert, R.M. Porras Blanco, G.B. Muniz. The effects of smokeless cookstoves on peak expiratory flow rates in rural Honduras, Journal of Public Health, 2015, 455-460, DOI: 10.1093/pubmed/fdu087