EXPOSURE ASSESSMENT FOR A RURAL COMMUNITY USING BIOMASS FUEL IN TRADITIONAL AND IMPROVED STOVES

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1 EXPOSURE ASSESSMENT FOR A RURAL COMMUNITY USING BIOMASS FUEL IN TRADITIONAL AND IMPROVED STOVES RS Patil * and S Dash Centre for Environmental Science and Engineering, Indian Institute of Technology, Bombay, Mumbai ABSTRACT In developing countries biomass fuels are burnt mostly in primitive stoves causing serious implications for exposure and health. To overcome this problem, the most common intervention attempted is the introduction of improved smokeless stoves. The performance of these new stoves is tested under controlled conditions but there is a dearth of data under field conditions. The objective of this study is to evaluate the effectiveness of the improved stoves in terms of personal exposure in a rural community. In the study Respirable Particulate Matter (PM 5 ) and CO were monitored on a longitudinal basis i.e., before and after the introduction of intervention (improved stove). Results show improved stoves reduce average PM 5 concentrations by 37% for personal sampling and CO concentrations by 54% near the stove during cooking period. For the community as a whole there is an average 40 % reduction in daily-integrated exposure to PM 5 with the improved stoves (p<0.0001). INDEX TERMS Exposure assessment, Improved stoves, Biomass fuel, Respirable Particulate Matter (PM 5 ), Field experiments INTRODUCTION In a country like India, the problem of indoor air quality faced by a huge population is the usage of biomass as cooking fuel (Saksena, 1999; Prasad, et al., 1992). It is estimated that 76% of total households and some 90% of rural households in India still rely primarily on biomass fuel. It has also been estimated that 410, ,000 premature deaths annually occur in India from indoor air pollution exposures to children under five and adult women (Smith, 1998). To overcome this problem, the most widely applied intervention is the introduction of improved stoves that emit less pollutants than traditional stoves. The Government of India's National Programme of Improved Cookstoves (NPIC) has introduced some 33 million biomass based improved stoves in rural areas during (Indoor Air Pollution, ESMAP News Letter, 2001). Initial work on benefits of improved stoves was often marked by measurement of efficiencies and emissions in controlled environments. More recently, the attention of research community has shifted from such ideal operating conditions to monitoring stove operation and performance under actual conditions. Only a handful of studies, however, have evaluated the reduction in pollution achieved by these cookstoves (Ezzati, et al., 2000; Naeher,et al., 2000). Still no longitudinal study is available regarding detailed exposure assessment for the households switching over to improved stoves, although it is recognized that exposure assessment is a better indicator of health risk (Kulkarni and Patil, 1999). * Contact author rspatil@cc.iitb.ac.in 572

2 Thus, the objective of this study was to evaluate the effectiveness of new smokeless stove in reducing the level of pollutant exposure. This was achieved by conducting detailed dailyintegrated exposure assessment using microenvironmental approach in the selected households, which use biofuels like cowdung and wood. The monitoring was done on longitudinal basis i.e, before and after the introduction of improved stoves. The target group included all the members of a household working within the village. This assessment was done for Respirable Particulate Matter (PM 5 ) and CO, which are appropriate indicators of biofuel smoke. METHODS The site chosen for the study was village Eksaal, in District Raigad of Maharashtra where the major occupation of the villagers is agriculture. The village does not have any industry and the nearest one is around 5 km away. Very few vehicles ply through the village. Hence, the most important source of air pollution is domestic household cooking. This was the reason for selecting this village so that exposure and therefore the health effects due to the use of biofuels for domestic cooking can be delineated. Most of the houses in the village are tile roofed and few have roofs made of cement concrete and asbestos. The walls of houses are mostly made of bricks or bamboo and mud. There are about 150 houses in the village and total population is The villagers use biofuels like cowdung and wood for domestic cooking purpose. In the initial phase to start the fire they use 25 to 30 ml kerosene. Fifty households had been identified for installation of improved cook stoves under NPIC. From these for the purpose of this study 14 households were selected based on stratified random sampling procedure because this technique ensures that the sample will be representative of the selected traits i.e., type of house. While selecting the households, factors like the readiness to participate in the monitoring program, number of infants and aged persons, location of kitchen, ventilation parameters and habits of people were considered. Care was also taken to ensure that the houses are distributed throughout the village. Most of the houses have one living room cum bedroom and the kitchen is attached to it. Generally people keep doors and windows open all the time except during night while sleeping. The fireplace is located at the corner of the kitchen and cook faces East direction while cooking. Every house has electricity connection and villagers use it for lighting purpose. Monitoring The main objective of the study was to estimate exposure while cooking with two types of stoves. But since emissions during cooking can effect indoor air pollutant concentration during non-cooking hours also, daily-integrated exposure of individuals is also estimated which is a better indicator of health risk. The cumulative exposure would account for both indoor and outdoor exposures. The assessment is as follows: i n E ( T ) = C t (1) j= 1 j ij Proceedings: Indoor Air 2002 where E i is the exposure of ith individual, C j is the concentration of the pollutant measured in the jth microenvironment, t ij is the time spent by ith individual in jth microenvironment and T is the total time period. Exploratory surveys helped in identifying the predominant microenvironments for the target group. These turned out to be eight in number viz.kitchen during cooking, living room during cooking, kitchen during no cooking, living room during no cooking, living room during sleeping hours, village outdoor where people collect water and spend some leisure time, village outdoor far away from the residence like agricultural 573

3 field and village indoor in school where students go for study during day time. Kitchen and living room during non-cooking hours and sleeping duration constitute the indoor back ground. A protocol was designed to ensure minimum disturbance of the normal conditions. For assessing cook s exposure during the cooking, the personal sampler was attached to her waist and the cyclone pinned to her shoulder. CO was measured only during cooking sessions at a horizontal and vertical distance of 0.5 meter and 0.6 meter from the stove respectively. During cooking sessions samplers were switched on a minute before the fire was lit, and switched off a minute after the fire was extinguished. For area sampling the personal samplers was kept at the center of the room, at the breathing level. In each house all indoor microenvironments were monitored twice in a day except sleeping, which was monitored on two consecutive days with separate filters. In order to have a comparative daily-integrated exposure assessment, a two-phase monitoring programme in the selected houses was done on a longitudinal basis i.e., before and after the introduction of improved stoves. The traditional stoves are two/three pot mud stoves and the improved stove, Laxmi is a two-pot cement concrete cookstove with chimney. It has been developed by Technical Backup Unit (TBU) of Appropriate Rural Technology Institute (ARTI) Pune, India (Karve, 1994). The daily movement profile of the respondents was noted through recalled based questionnaire on longitudinal basis. The other confounding factors like, type of fuel, time of monitoring, opening of door and windows, cooking by same member, pot type etc. were kept constant for both the phases to eliminate their effects so that any change in concentration can be attributed to type of stove only. A personal air sampler, based on gravimetric principle, (of SKC make, model 224-PCXR7) was used along with an aluminum cyclone to measure levels of PM 5 (Respirable Particulate Matter). The cyclone has 50% removal efficiency for particle median diameter of 5µm (d 50 ) at flow rate of 1.9 lpm. Polycarbonate membrane filters of 37-mm dia with pore size 0.8 µm was used after desiccating them with silica gel for 24 hours. CO was measured using miniature samplers (National Dragger, model 190 Data logger; 1-ppm accuracy). Temperature and humidity were also measured in each experiment using a whirling psychrometer. A digital anemometer was used to measure wind speed through the openings like doors and windows in the house and outside the house at regular intervals. RESULTS AND DISCUSSION Independent variables are stove types measured at ordinal level and duplicate samples measured at nominal level. The dependent variables are RPM and CO concentrations in various microenvironments measured at interval-ratio level. Data on concentration levels of RPM in various microenvironments and levels of CO in kitchen with cooking are given in Tables 1 and 2. Indoor background is indoor environment when no cooking is done. A twotailed independent samples t-test indicate that there are no significant variations in RPM and CO of the duplicate samples during the cooking sessions and RPM in indoor background (p>0.2). From the data during cooking sessions it is observed that 25-percentile line of concentration levels of traditional stoves is above the 50-percentile line of concentration levels of improved stoves, so there is reason to conclude that the two population means may be different. Results show that during cooking sessions concentration with improved stoves is much lower than that with traditional stoves both for RPM and CO. The reduction in mean RPM concentration with the improved stoves is 37 % for personal sampling (p=0.021), 54% for area sampling in kitchen (p=0.0026) and 35% for area sampling in living room (p=0.0034). The reduction in mean CO concentration is 54% with improved stoves (p=0.0087). So reduction in concentrations with improved stoves in comparison to traditional 574

4 stoves is statistically significant (p<0.05) for matched pair t-test. For indoor background the test result indicates that improved stoves do have a statistical significant impact over RPM concentrations in the kitchen during non-cooking hours also (p=0.008). Reductions in RPM concentrations for indoor background in living room during day and during sleeping are not statistically significant (p= 0.41 and 0.16). Also it was observed during experiments that RPM concentrations are a function of factors like orientation of the house, location of stoves, type of roof, volume of kitchen and wind direction and their significance needs to be studied. Table 1. RPM (PM 5 ) concentrations in various indoor microenvironments Microenvironment type Traditional Stoves Improved stoves n Conc. C.I. n Conc. C. I. Indoor Cooking Personal sampling (cook) ± ± Area sampling (kitchen) ± ± Area sampling (living ± ± room) Indoor Background Area sampling (kitchen) ± ± Area sampling (living ± ± room) Area sampling for sleeping (living room) ± ± Note: a) n is number of observations, b) C.I is 95% confidence interval estimate Table 2. CO Concentration (ppm) in kitchen Microenvironment type Traditional Stoves Improved Stoves n Conc. C.I. n Conc. C.I (ppm) (ppm) Kitchen, Cooking ± ± While sampling indoors the outdoor microenvironment outside the house was concurrently sampled near breathing level heights (n=18, 90 µg m -3, 95% C.I µg m -3 ). Sampling for RPM was also done in agricultural fields at a suitable time (n=5, 47 µg m -3, 95%C.I µg m -3 ). On two consecutive days sampling was done in village school during school hours (n=7, 47 µg m -3, 95% C.I µg m -3 ). The results indicate that mean outdoor RPM concentration is lower than the National Ambient Air Quality Standards (NAAQS) for PM 10 (i.e,100 µg m -3 ) in residential and rural areas. Outdoor concentration at relatively faraway places like agricultural field is nearly 50% lower than the outdoor concentration near by the households. This may be due to the household emission sources. Exposure assessment A recall-based questionnaire was used to determine how much time individuals spend in various microenvironments. Using the time budget analysis of the respondents collected in daily time activity pattern data sheets and concentrations of RPM measured in various microenvironments the integrated exposure was determined with Eq. (1). Mean daily integrated exposure of 56 members of 11 households to RPM comprising exposure from cooking, indoor background, village school and outdoor, for traditional and improved stoves are given in Table 3. It is seen that cooking activity contributes 62% and 48% of daily 575

5 exposure to RPM in case with traditional stoves and improved stoves respectively. The results for all respondents show that there is an average 40 % reduction in daily-integrated exposure to RPM with the improved stoves compared to traditional stoves. In case of exposure due to cooking there is an average 54 % reduction in exposure to RPM. A two tailed matched pair t- test suggests that reduction in both daily-integrated exposure and exposure from cooking due to improved stoves is statistically significant (p<0.0001). The average daily-integrated exposure in concentration units is 200 µg m -3 and 118 µg m -3 for traditional stoves and improved stoves respectively. Table 3. Exposure assessment with stove types Stove type RPM Exposure (mg h m -3 ) Cooking Indoor background Daily integrated Traditional Stoves 2.97 ± 2.57 ( ) 1.46 ± 0.67 ( ) 4.79 ± 3.0 ( ) Improved Stoves 1.37 ± 1.25 ( ) 1.11 ± 0.31 ( ) 2.85 ± 1.32 ( ) Note: Value in the parenthesis represents 95% confidence interval Average RPM exposure (mg h m -3 ) of demographic subgroups Various demographic subgroups classified under age, gender and occupation have varying mobility pattern, and hence experience different RPM concentrations and different exposure across a day. Using the time budget study and RPM concentrations in various microenvironments average RPM exposure of demographic sub groups is calculated as given in Table 4. Table 4 Average RPM exposure (mg h m -3 ) for demographic subgroups Age groups Gender Exposure types Traditional Stoves Improved Stoves 0-6 M(6) Daily integrated 4.88 ± ± 2.16 Cooking 3.12 ± ±1.80 F(4) Daily integrated 4.47 ± ± 0.38 Cooking 2.93 ± ± M(7) Daily integrated 4.24 ± ± 1.40 Cooking 2.61 ± ± 1.38 F(9) Daily integrated 4.66 ± ± 1.20 Cooking 2.80 ± ± M(8) Daily integrated 3.60 ± ± 0.81 Cooking 1.98 ± ± 0.77 F(15) Daily integrated 5.95 ± ± 1.56 Cooking 3.89 ± ± M(3) Daily integrated 4.90 ± ± 0.39 Cooking 2.62 ± ± 0.23 F(4) Daily integrated 2.79 ± ± 0.29 Cooking 1.45 ± ±0.55 Note: Value in parenthesis represents number of respondents, M: Male, F: Female 576

6 It is observed that all the age groups have a lower RPM exposure with improved stoves. Females of age group comprising mostly cooks experience maximum daily exposure to RPM both with traditional as well as improved stoves, though with improved stoves there is an average 42 % reduction in exposure (p<0.05). Infants also have a high RPM exposure. Females of age group 60-experience lowest RPM exposure, because they seldom go to kitchen. Males of age group have a low exposure to RPM both with traditional and improved stoves, as they stay for more time outdoors. CONCLUSIONS The purpose of the study was to assess the exposure reduction potential of improved stove in field conditions. It was observed that exposure, which is a function of concentration and time activity pattern of members of households was found to reduce significantly with the improved stoves, thus justifying its utility. Also an average reduction of daily cooking hours by 20% and fuel use by 35% was observed. Thus there is a potential of biofuel conservation and exposure reduction with the use of improved stoves by households. However, this study needs to be repeated after a suitable period to check the efficacy of the improved stoves with prolonged use. ACKNOWLEDGEMENTS This study is a part of a project undertaken by Indian Women Scientists' Association, Mumbai under aegis of MNES, Government of India. We are thankful for the ground level logistic support and coordination rendered by the Association. REFERENCES Ezzati M, Mbinda B. M, and Kammen D. M Comparison of Emissions and Residential Exposure from Traditional and Improved Cookstoves in Kenya. Environmental Science and Technology. Vol 34, pp Indoor Air Pollution, Energy and Health for the Poor, News Letter Energy Sector Management Assistance Programme (ESMAP), The World Bank. Kulkarni M.M, and Patil R.S Monitoring of Daily Integrated Exposure of Outdoor Workers to Respirable Particulate Matter in an Urban Region of India. Environmental Monitoring and Assessment. Vol 56, pp Karve P, The Laxmi Stove, Appropriate Rural Technology Institute, Pune, India. ( Prasad R, Pal R. C, Saksena S. and Joshi V Patterns of Daily Exposure to TSP and CO in the Garhwal Himalaya. Atmospheric Environment. Vol, 26A pp Naeher L. P, Leaderer B. P, and Smith K. R Particulate Matter and Carbon Monoxide in Highland Guatemala: Indoor and Outdoor Levels from Traditional and Improved Wood Stoves and Gas Stoves. Indoor Air. Vol, 10 pp Saksena S Integrated Exposure Assessment of Air Borne Pollutants in Urban Community Using Biomass and Kerosene Cooking Fuels, PhD Dissertation, CESE, IIT Mumbai. Smith K. R Indoor Air Pollution in India: National Health Impacts and Cost- Effectiveness of Intervention: Indira Gandhi Institute of Development Research, Mumbai. 577