Indoor Air Quality and ventilation assessment of rural mountainous households of Nepal

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Original Article/Research

Indoor Air Quality and ventilation assessment of rural

mountainous households of Nepal

Indira Parajuli

a

, Heekwan Lee

a,⇑

, Krishna Raj Shrestha

b

a_{School of Urban and Environmental Engineering, Incheon National University, 406-772, 119, Academy Street, Yeonsu-gu, Incheon, Republic of Korea} b_{Research Centre for Applied Science and Technology, Tribhuvan University, Nepal}

Received 28 February 2016; accepted 25 August 2016

Abstract

Cooking with open fire has been crucial for occupants’ health due to poor Indoor Air Quality (IAQ) in most of the rural households. IAQ is affected by many factors, such as firewood moisture, stove type, ventilation, etc. A monitoring system has been developed to find the general IAQ with Improved Cooking Stove (ICS) and Traditional Cooking Stove (TCS). Decay curve technique is utilized to calcu-late the Carbon Monoxide (CO) decay time. A preliminary health survey is also carried out to evaluate the dweller’s health complaints. The study is carried out in two adjoining remote villages of Palpa District in Western Nepal.

The mean CO and PM2.5concentration for ICS and TCS are 27.11 ppm and 825.4lg/m3(27.11 ± 14.24 ppm and 825.4 ± 730.9lg/ m3_{) with significant correlation (}_p_{< 0.0001) and 36.03 ppm and 1336}_l_g/m3_{(36.03 ± 19.06 and 1336 ± 952.8) with significant correlation} (p< 0.0481), respectively. From the overall sample, the mean CO and PM2.5concentration is reduced by 29.9% and 39%, respectively. The ventilation analysis result shows more than an 80 percentage deficit in ventilation as per the minimal rate of ventilation as prescribed by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Moreover, the placement of chimney at a short vertical height of 1.2 m adjoining to back window is the major cause of backflow. Therefore, the study has recommended a greater focus on ventilation to control IAQ of rural mountainous households.

Keywords: Carbon Monoxide; Particulate matter; Indoor Air Quality; Air Exchange Rate; Ventilation

1. Introduction

Indoor air pollution (IAP) from ineﬃcient cooking prac-tices is a critical environmental health problem worldwide as half of the world population relies on biomass fuels for cooking and space heating inside their homes.

Accord-ingly, IAP contributed to 1.6 million of premature deaths/ year occurred in developing countries, with 8700 deaths occurring in Nepal alone, being the 4th leading cause of death (World Health Organization, 2016). Two million children under age of ﬁve die from Acute Lower Respira-tory Tract Infection (Warwick and Doig, 2004).

In Nepal, around 78% households are still solely reliant on solid biomass fuels for cooking and space heating pur-poses (NLSS, 2011/2012). Cooking and heating with solid fuels on open ﬁres or a traditional stove results in high con-centration of IAP. Indoor smoke contains a high range of

http://dx.doi.org/10.1016/j.ijsbe.2016.08.003

⇑ Corresponding author. Tel.: +82 (0)32 835 8468; fax: +82 (0)32 777 8468.

E-mail address:airgroup@incheon.ac.kr(H. Lee).

Peer review under responsibility of The Gulf Organisation for Research and Development.

H O S T E D BY

Gulf Organisation for Research and Development

International Journal of Sustainable Built Environment

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health damaging pollutants such as PM, CO, etc. In poorly ventilated kitchens, indoor smoke exceeds the acceptable concentration for Total Suspended Particles (TSP) by more than 100 times the standard limit (Dhakal, 2008). Acute Lower Respiratory Infections (ALRI), Chronic Obstruc-tive Pulmonary Diseases (COPD) and Tuberculosis are among the top 10 causes of death caused by IAP in a con-text of Nepal.

A Study carried out in Jumla, Nepal shows that 8 h and 24 h TSP and CO concentration are found to be 8420lg/ m3and 13.5 ppm; 5000lg/m3and 23.42 ppm, respectively (Hessen et al., 2004). This high concentration causes low birth weight and infant mortality (WHO, 2005; Warwick and Doig, 2004) as women usually continue preparing meals throughout pregnancy, the developing fetus is also indirectly exposed. Moreover, children often spend their time near their mothers while they are engaged in cooking tasks. Therefore, women and young children are dispro-portionally affected by the high concentration of pollutants accumulated inside their homes. The size distribution of PM is influenced by the fuel burning rate and air supply conditions with average emission factors for PM (3.84 ± 1.02), organic carbon (0.846 ± 0.895), elemental carbon (0.391 ± 0.350) from burnt corn straw in a residential cooking stove (Shen et al., 2013). A study in 18 villages byDavidson et al. (1986) has revealed the TSP (8800lg/ m3), CO (21 ppm) and N2O (368 ppb), where firewood is used as fuel (WHO & Nepal Health Research Council, 2002). The indoor air concentration with TCS in the rural part of Nepal was reported very high (Davidson et al., 1986; Nepal Health Research Council, 2004; Reid et al., 1986). Thus, IAP concentration in Nepalese houses is much higher than the standard permissible value for safe health. Large segments of people are still dependent on simple primitive, less efficient and locally fabricated biomass fuel and combustion devices in the household, rural industries and commercial sectors. These devices are prone to emit IAP that subsequently pollutes the atmosphere and cause many diseases. For example, the measurement of PM10 concentration monitored by Nepal Environmental & Scien-tific Services (NESS, 1999) in city core, sub-core, remote and industrial areas of Kathmandu for firewood burning houses are found to be 6 and 2.4 times greater than LPG and kerosene burning houses, respectively (Ministry of Population and Environment-MOPE, 2001). Pandey et al. (1989) measured hourly average personal exposure concentration of Respirable Suspended Particulates (RSP), CO and formaldehyde (HCHO) during cooking periods in 20 households with TCS and ICS in rural areas of Nepal’s hilly region from November 1986 to March 1987. The result shows the concentrations of RSP, CO and HCHO as 8200lg/m3, 82.5 ppm and 1.4 ppm for TCS, respectively, whereas the concentrations of RSP, CO and HCHO for ICS are as 3000lg/m3, 10.8 ppm and 0.6 ppm respectively.

The concentration of IAPs originating from the burning of solid fuels depends on a number of factors such as fuel

type, characteristics of housing and methods of cooking. Depending on cooking activities, the extent of pollutants can vary from day to day and even within the day (Ezzati and Kammen, 2001). The researchers have reported comparative analysis of pollution concentration between TCS and ICS in diﬀerent studies globally ( Armendariz-Arnez et al., 2010; Singh et al., 2012).

In order to control IAP, constructions of better-ventilated rooms are as important as using improved stoves and fuels. According to a comparative study conducted by

Reid et al. (1986), the mean personal exposure to TSP in TCS and ICS were 3920lg/m3 and 1130lg/m3, respec-tively. Similarly, the mean personal exposure to CO in TCS and ICS was 380 ppm and 67 ppm, respectively. This implies that ICS reduces indoor TSP and CO concentration by 71% and 82%, respectively.

This study has mainly focused on CO and PM2.5 pollu-tant concentration in households with ICS and TCS sepa-rately, assessed the ventilation requirement and effect of backflow. The result of this study will be helpful to assess the health damage caused by IAQ as well as the ventilation improvement to prevent backflow. For this, the main objective of this study is to quantify the 24 h PM2.5 and 12 h CO concentration in houses having both ICS and TCS to assess whether the indoor concentration is within safe threshold for resident health. The results are compared with different standard guideline values for safe health con-ditions. This can help to predict the health implications due to IAQ. Moreover, the CO lagging time is estimated and discussed with the available ventilation (opening areas) as well as the rate of ventilation required for IAQ improve-ment, suggesting better ventilation along with improved stove types. While designing the ventilation, the particular focus should be given to smoke backflow to prevent reentry of the smoke inside. However, this paper has limitation about the technique of efficient ventilation, energy conser-vation and efficient burning.

2. Materials and methods

2.1. Study site

The study was conducted in rural settlements i.e. two VDCs: Khasauli and Bhairabsthan of Palpa (28°40000N 83°150000E with an altitude of 1838 m, i.e. mid-hills with temperate climate), district of western Nepal as shown in

Fig. 1. The Bhirabsthan VDC is 9 km and the Khasauli VDC is 11 km away from Tansen (Headquarter of Palpa District). These VDCs are situated at southeast of Tansen and 38 km away from Siddartha highway. The main source of cooking fuel in these settlements is ﬁrewood available from community forest. The majority of the households have ICS rather than TCS.

Altogether 40 households were selected randomly for questionnaire survey. All of the participating households responded to the questionnaire revealing details on stove types, health complaints, and other general data.

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More-over, 32 sampled measurements were performed in 16 households (10ICS + 6TCS) for monitoring the IAQ data. The sample size design is based on statistically signiﬁcant diﬀerence in representative household structures having ICS and TCS. Pollutant concentrations are monitored con-tinuously for a whole day for each of the sampled houses.

2.2. Indoor air pollution monitoring

IAQ was assessed by continuous monitoring for 24 h in a sampled household applying sampling protocol devel-oped by the Center for Entrepreneurship in International Health and Development (CEIHD), University of Califor-nia, Berkeley. The assessment was conducted based on daily use of stove for preparing two major meals in the morning and evening, and a short meal (fast food) in the afternoon in sampled households. CO and PM2.5 were taken as key indoor air pollutants, which are epidemiolog-ically important indicators of IAP (WHO, 2002, 2005). These are the serious pollutants for indoor environments produced while cooking with ﬁrewood burning. Hence, PM2.5and CO are on major focus in this study.

The pollutants were monitored inside kitchens where people mostly burn ﬁrewood for cooking. CO was mea-sured using CO T82 data logger that records the CO data with the interval of every one-minute throughout measure-ment period. The PM2.5 was measured using PM buck pump set (Model LP-5) with buck calibrator having pump-ing rate 2200 ml/min. The cyclone with ﬁlter cassette

hav-ing filter size 37 mm and 0.8l pore size was used for PM2.5 sampling. A single separate filter, which was pre-weighted before administering it into monitoring opera-tion, was used for each of the sampled households. The fil-ter was replaced affil-ter completing the monitoring task to apply it into the next house. The filter paper was dried for 3 h at 105°C in a vacuum oven then left to cool in a desiccator with silica gel for 30 min to protect from mois-ture and each sampled filter paper was weighted separately. Thus, the total weight of filtered PM2.5 was obtained by weighing each sampled filter individually. Mean concentra-tion of PM2.5 was identified by dividing the resultant weight with total volume sampled by buck pump through-out individual sampling duration.

2.3. House structure and orientation

Generally, the houses are of single cell types having the kitchen and living room within the same enclosure. The enclosure is made up of mud and stone – wall with galva-nized inclined (30°) iron sheet roof. Generally, there are two windows, one at the front part and the other at the back part of the house as shown inFig. 3(a) and (b). People usually burn ﬁrewood inside the enclosure. About 60% of households were using ICS whereas about 40% of the households were using TCS. The houses using TCS have not any particular ventilation for the extraction of pollu-tants from the enclosure, whereas the houses with ICS have 1.2 m high chimney attached with stove as shown inFig. 2. Figure 1. Geographical position of study area and speciﬁc location of study site.

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Generally, chimney outlet was placed at the back wall nearby the back window. In the mountainous region, most houses are facing toward the south and a few of them are east facing.

2.4. Ventilation analysis

Ventilation rate is calculated using mass balance model considering a house as a box with specified volume. The box model can be established with the assumption of room air being well mixed. For this, the peak concentration was observed while the fire is extinguished after completion of lunch cooking at 9.00 am. It was suggested to dwellers that they should turn off the fire completely and immediately take out the remaining firewood outside to assure no more

additional release of CO inside kitchen. The continuous reading was then observed until the CO concentration drops considerably down. The indoor–outdoor (I/O) Air Exchange Rates (AER) were calculated in a normal condi-tion based on I/O contaminant concentracondi-tion by the decay method using algorithm. The similar model has adopted by

You et al. (2012).

Vdc

dt ¼Q:CoQ:CðtÞ þSK:CðtÞ ð1Þ

where, dc/dt= change in concentration with time; Co= -outdoor contaminant concentration; C(t) = indoor con-taminant concentration; Q= air ﬂow rate; S= indoor emission source contamination; K= ﬁrst order degrada-tion constant.

Figure 2. Cooking with solid fuel in improved and traditional cook stove of study site.

(a) (b)

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In conservative equation K= 0, if there is no indoor source then Eq.(1) would be as below

Vdc dt ¼Q:CoQ:CðtÞ ð2Þ By integration of Eq.(2) CðtÞ ¼Coþ½Cð0Þ Co:e Q Vt ð3Þ

where,C(0): indoor CO concentration at timet= 0;Q/V: Air Exchange Rate (AER).

Then the Eq.(3)written as:

AER¼1 t ln Cð0Þ _Co ð Þ CðtÞ Co ð Þ ð4Þ

2.5. Data collection techniques 2.5.1. Questionnaire survey

The survey was conducted to identify the factors influ-encing the concentration of IAPs inside the kitchens of 40 sampled households. The questionnaire-set was designed for collection of information on cooking activities and factors affecting high smoke concentration in the kitchen during the cooking time. The questionnaire included: stove type and condition, type of fuel they used, condition of fuel used, size of family, number of children younger than 5 years of age, total firing duration per day, cooking duration for each meal, ventilation (number and size of windows, doors, eaves), roof type, floor and wall materials. The questionnaire was administered once in each household before installing the monitoring instruments.

The survey was carried out in houses with TCS and ICS in operation separately, enquiring about the functioning of ICS and TCS for a comparative analysis of ICS and TCS performance, as well as their contribution to IAQ. The fol-lowing speciﬁc questions were asked of respondents: (1) Cause of installation of ICS? (2) Which stove is easier to handle? (3) Whether ICS is time saving? (4) Does ICS require lesser amount of fuel? (5) Health complains while cooking with TCS? (6) Is ICS less polluting? Moreover, the positive and negative aspects of TCS and ICS were evaluated among the women as they are engaged for the cooking job in the study area.

Additionally, the questionnaire based on health survey was also carried out to identify the separate health impact of both types of houses having ICS and TCS. Question-naire includes questions about respiratory health symp-toms of the mother (usually the cook) and the children below 5 year old who stay usually around their mother. The respondents were chosen based on their involvement in cooking operation from each sampled households.

2.5.2. Physical data monitoring

The monitoring was carried out by installing the moni-toring instruments in the house to draw the status of the stove, operation way and quantity of ﬁrewood they use. Additionally, movement of the children during cooking

operation, time spent during cooking, cleanliness and posi-tion of stove and chimney, routes of exhaust of soot, wind direction, etc. were observed constantly during the survey.

3. Results and discussion

Both PM2.5and CO are measured in 16 households hav-ing TCS (n= 6) and ICS (n= 10). The results show that the indoor concentrations for both pollutants in the holds with ICS are comparatively lower than in the house-holds with TCS. However, the concentrations from both types of stove have exceeded the threshold value recom-mended by various organizations for safe health.

The health results include a comparative tabulation showing prevalence of health symptoms in stove user dur-ing TCS and ICS operation based on their health complaints.

3.1. Status of IAP in indoor spaces (village houses)

The reduction in concentration between TCS and ICS are 29.9% for CO concentration and 39% for PM2.5 as shown in Table 1. The mean concentration of CO for ICS and TCS are 27.11 ppm and 36.03 ppm, respectively. This shows that there is significant reduction (p= 0.0086) in the CO concentration from ICS as compared with TCS. Likewise, mean PM2.5 concentration for household having ICS is obtained 825.4lg/m3while the mean concen-tration is found significantly higher (p= 0.0086) in house-holds with TCS i.e. 1336lg/m3. The overall comparative correlations between 24 h mean PM2.5and 12 h mean CO have found strong positive correlation with (R2= 0.84), (n= 16) andp value <0.01 as shown in Fig. 5. It signifies that PM2.5 and CO are generated from the same source, as cooking stove is a significant source in the study area.

The Fig. 4shows that CO and PM2.5 concentration of households having both ICS and TCS are higher than the WHO permissible values of 8.732 ppm and 25lg/m3 respectively. Generally, the CO concentration for 12 h and PM2.5 concentrations for 24 h monitoring period in the similar households are peaked together as both pollu-tants are produced during combustion of ﬁrewood while cooking.

The reduction in 8 h average CO concentration from ICS to TCS is found to be 17.3%, as shown in Table 2. The relative reduction of pollutant concentration in ICS in comparison to TCS is found not that remarkably diﬀer-ent as reported in an average reduction of concdiﬀer-entration while comparing it with permissible standard value. The values for both types of stove are found to be higher than WHO permissible value as shown in Fig. 5. Hence, the indoor environment is found harmful for both houses hav-ing TCS and ICS.

The relative reduction in concentration of pollutants for ICS shows that ICS are better than TCS. This result is also supported by the questionnaire survey result as shown in

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polluting, time saving and consuming less ﬁrewood than TCS. The similar result is found in a social survey, with a questionnaire, where most of the women of the study area have revealed that ICS is better than the TCS in terms of handling, lower concentration, ease in cooking, time saving and fuel eﬃciency (Singh et al., 2014).

However, the permissible value for safe health in both types of stove has surpassed the standard. Therefore, the ICS and the performance of Chimneys are found to be less eﬃcient. This shows that the reduction in CO concentra-tion is due to changes in quality of fuel rather than the per-formance of chimney and ICS. The recent study carried out by Aprovecho Research Center (ARC), USA also showed that chimney stoves are less eﬃcient as it is slower to boil and consume more fuel. Furthermore, the indoor pollutant concentration has not been reduced as per the permissible value. Therefore, the invisible PM2.5, CO and powerful cli-mate forcing pollutants (methane and black carbon) are still being emitted excessively inside rural household.

From the questionnaire survey, around 75% households were found to have complained about the ICS performance as it consumes more firewood and difficult in burning fire-wood properly. Thus, it emits high smoke that is accumu-lated inside the house rather it exhausted out from the chimney. The orientation of the stove inside the house with placement of the chimney at a low height adjoining to the window is found as one of the major reasons of backflow of polluted air inside. Hence, the concentration of pollution is found higher than prescribed by WHO and USEPA for houses even with ICS.

3.2. Air Exchange Rate and CO – decay time

CO – decay time is calculated while the source is com-pletely oﬀ and assured that no more additional release of CO prevails. The Air Exchange Rate (AER) is found in the range of 0.67–2.67 ACH for all sampled households as shown in Fig. 7. The values are small in comparison to the prescribed value of 5 ACH by ASHRAE. Moreover, airﬂow rate is also found below the recommended values for the local ventilation i.e. 8 l/s/p.

The total air required to ventilate the kitchen is based on concentration as well as minimum fresh air required per person and per square meter of floor area as per the ASH-RAE guideline calculated for each sampled houses to derive the air deficit for ventilating the room for healthy living. This also shows that the higher the concentration, the higher the air deficits to fulfill the ventilation demand of a house.

The amount of airflow rate required to ventilate the room in Cubic Feet Minute (CFM) for the houses having ICS and TCS is based on the mass balance method using Eq. (4) as shown in Fig. 8. The airflow rate available for the houses having TCS is found to be comparatively lower than houses with ICS. Therefore, fresh air required to dilute concentration for safe human health based on ASH-RAE guideline and deficit air for the houses having TCS is

Table 1 Imp roved co ok stove and tradi tional co ok stove 12 h C O and 24 h P M 2.5 conc entration data comparis on. Pollu tants type 8 h mean CO (ppm) 24 h P M 2.5 ( l g/m 3) 95% conﬁde nce inte rval (CI) Min M ax Mean Median Mode SD Range 95% conﬁde nce inte rval (CI) Min M a x M ean Median Mode SD Range IC S ( n = 10) 13.96 30.91 24.63 24.15 13.69 4.914 17.22 21.58 43–2 7.6757 259.6 2500 825.4 449.5 259.6 730.9 2240 1278 .42–3 72.383 TCS ( n = 6 ) 21.01 35.53 28.97 30.52 21.01 5.621 14.52 26.02 23–3 3.4677 468 3147 1336 1144 468 952.8 2679 2098 .4–57 3.601 Aggr ega te ch ange in % 17.3% 39%

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found to be a little higher, which is <10% (i.e. average required air ﬂow for house having TCS: 61.85CFM and house having ICS: 57.14CFM and average deﬁcit air for house having TCS: 49.89CFM and house having ICS: 44.56CFM). Hence, from this study, it is clear that venti-lation plays a vital role to maintain IAQ rather than stove type only.

The concentration of pollution is increased with the increase in emission rate with strong correlation (R2= 0.93). More airflow is required to accelerate the decay rate, i.e. the greater the airflow rate, the lower the pollution concentration accumulated inside the room as depicted in Fig. 9(a). As shown in Fig. 9(b), there is an inverse correlation between AER and CO decaying time withR2= 0.64. Therefore, it is apparent that the airflow rate plays a vital role to make indoor environment clean and hygienic rather than stove types only. The similar result is found in the IAP study of Honduran community as well that reveals ventilation factors, age of stove and stove scale predicting more than 50% of the variation in the personal and indoor PM2.5 and 85% of variation in indoor CO (Clark et al., 2009).

3.3. Health survey

The health survey was conducted with a total of 40 cooks having mean age 35 ± 10 (range of 22–51) operat-ing ICS and TCS separately, which compares the preva-lence of health symptoms because of their stove operation type. Moreover, 25 children below 5 years of age were surveyed. The key health problems they have experienced are coughing, chest pain, headache, diﬃculty in breathing, wheezing and irritation in eyes, as reported during the survey. The prevalence of key respiratory health symptoms in both women and children is reported lower in ICS users than in TCS users. Out of the total, 65% users have reported coughing problem during TCS use compared to 50% in that of ICS users. Chest pain complaints and diﬃculty in breathing are reported from 70% of cooks using TCS as compared to 55% ICS users. Figure 4. Correlation between mean CO ppm and mean PM 2.5lg/m3

concentration in sampled households (n= 16).

Table 2 Imp roved co ok stove and tradi tional co ok stove 8 h CO and 24 h P M 2.5 conc entration data comparis on. Pollu tants type 8 h mean CO (ppm) 24 h P M 2.5 ( l g/m 3) 95% conﬁde nce inte rval (CI) Min M ax Mean Median Mode SD Range 95% conﬁde nce inte rval (CI) Min M a x M ean Median Mode SD Range IC S ( n = 10) 13.96 30.91 24.63 24.15 13.69 4.914 17.22 21.58 43–2 7.6757 259.6 2500 825.4 449.5 259.6 730.9 2240 1278 .42–3 72.383 TCS ( n = 6 ) 21.01 35.53 28.97 30.52 21.01 5.621 14.52 26.02 23–3 3.4677 468 3147 1336 1144 468 952.8 2679 2098 .4–57 3.601 Aggr ega te ch ange in % 17.3% 39%

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Similarly, 85% TCS users have reported the problem of wheezing compared to 52% of ICS users. Eye irritation complaints are reported from 95% of TCS cooks as com-pared to 42% ICS cooks.

Regarding the matter of health concern of children, 40% of the respondents said that their children are regularly doing their homework inside the house. Hence, the data described above show that children are also exposed to

the respiratory diseases caused by poor IAQ that exceeds the WHO permissible guideline value for safe health.

Out of the total surveyed children below 5 year age group, 35% of them are with their mother during cooking time, 37% of them move in and out of the kitchen and rest 28% of them stay at other place during cooking. Health complaints such as fast breathing, wheezing and watery eye among children below 5 year age group are found to

0 500 1000 1500 2000 2500 3000 3500 0 5 10 15 20 25 30 35 40

ICS ICS ICS ICS ICS TCS TCS TCS TCS TCS ICS ICS ICS ICS ICS TCS

PM 2. 5 g/m 3 ) CO concentration (ppm ) Stove Types

8 hr Mean CO ppm PM2.5 ( g/m3) WHO 8 hr mean CO (ppm) WHO PM2.5 ( g/m3)

Figure 5. Comparison of CO and PM2.5concentration in houses with ICS and TCS in comparison to WHO permissible value.

0 10 20 30 40 50 60 70 80 Easy to handle (ICS) Time saving (ICS) Less polluting (ICS)

Fuel saving (ICS) Health complain (TCS) ICS installed in VDC Resonse % by respondent d Question Administrated

Figure 6. Response of dwellers in questionnaire survey (respondents from houses with TCS and ICS).

0 0.5 1 1.5 2 2.5 3 0 10 20 30 40 50 60 70 80

ICS ICS ICS ICS ICS TCS TCS TCS TCS TCS ICS ICS ICS ICS ICS TCS Air exchange

rate/ hour Average CO Concentration (ppm ) Stove types 12- hr mean conc AER (/hr)

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be similar with both of ICS and TCS users. The compara-tive health survey similar to this study has been reported in

Nepal Health Research Council (2004) and Practical Action (2007). The study has found higher reduction in prevalence in cough, phlegm, headache and eye irritation.

3.4. Comparison between IAP of TCS and ICS

Pollution concentration of the sample households with TCS and ICS exceeds the permissible value of CO for 8 h average concentration. The study has reported the 12 h mean, which includes the time during the non-operation of the stove as well. However, the air concentration with ICS is found lower in comparison to that of concentration with house having TCS.

For PM2.5, all the surveyed households having TCS and ICS exceeds the WHO permissible value for safe health. Most of the sampled households have placed their outlet of the chimney just beside the window at a height of 1.2 m only, which allows the smoke to return back into house.

There are various reasons for exceeding the permissible concentration as noticed during the study period, such as the number of windows and doors, dryness of the firewood they use, orientation and placement of chimney for ICS, opening or closing of the windows during cooking time, etc. The other studies carried out by Aprovecho Research Center (ARC), USA, 2008 show that even though ICS reduces overall warming impact by as much as 50–95%, the products of incomplete combustion (PIC) is still there. Therefore, the reality is that the efficient stoves are often unclean and the clean stoves are often inefficient as they

consume more fuel wood than the traditional stove without chimney. Moreover, the indoor pollutant concentration has not been reduced as per the permissible value.

Households having a higher IAP concentration than the WHO permissible value need quick intervention to reduce the concentration in the house. The most feasible way to control IAQ observed in this study is through the improve-ment of ventilation. This study observes that eﬃcient ven-tilation for houses would be the best way to solve the problem of IAP. The role of ventilation has also been sup-ported by various studies (BalKrishnan et al., 2004; Dasgupta et al., 2006; Huq et al., 2004). Moreover, the bet-ter combustion technology and automatic wood burning stoves are suitable for low-carbon dwellings and meet the remaining heat demand (Carvalho et al., 2013). Open or well-ventilated kitchen conditions lower the concentration. It is better to adopt such kitchen settings (by the means of poor family) rather than switching to more expensive clean fuels to cost eﬀective cleaner fuel in the rural areas (Begum et al., 2009).

It is possible to maintain good thermal condition with reasonable airﬂow rate with ventilated ceiling (Akimoto et al., 2002). The capture of contaminant eﬃciency with the ceiling height of 2 m can be as high as 85–95% and with 2.3 m ceiling height, it is 80–85% (Risto and Mustakallio, 2003).

4. Conclusion and recommendation

Higher concentration of IAP is found from burning of fuel wood in both households having ICS and TCS, partic-ularly in those houses with poor ventilation arrangements. 0 5 10 15 20 25 30 35 40 45 50 55 60 65

Air flow (avilable) in CFM Breathing zone outdoor air flow required

in CFM (ASHRAE) Volume Air deficit CFM

Air flow rate in CFM

TCS ICS

Figure 8. Comparative airﬂow required for ventilation in kitchen based on ASHRAE standard.

y = 1.4801x - 12.152 R² = 0.9372 0 20 40 60 80 100 120 0 20 40 60 80 Em ission rate (m g/sec) Mean CO Concentration in ppm a) Mean CO concentration Vs. emission rate

CO decay

tim

e

(hr)

Air exchange rate (/hr)

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Thus, it follows the adverse health complaints to the people of the study area. The reduction of IAP (concentration of CO and PM2.5) in TCS and ICS are over 29.9% and 39%, respectively. This indicates that ICS helps to reduce amount of pollutants in comparison to that of TCS despite the fact that it cannot ensure the healthy condition. The effect of back flow is a major problem found in a chimney of a short height nearby a window that allows pollutants back into the house. Therefore, the future research should focus more on technical chimney orientation and height to prevent backflow problems.

The findings of this study show that ICS is better in comparison to TCS operation in respect to concentration. However, the ventilation plays the vital role to control IAQ as the CO lagging time is found to be comparatively less with a faster decay rate in houses having a higher air-flow rate. The ventilation analysis results show that most of the houses are in deficit of ventilation. It has found an almost 80% deficit in ventilation in sampled houses based on concentration of pollutants. However, this huge amount of ventilation requirement is not practical to solve the problem. Therefore, this study recommends for the replace-ment of TCS with ICS focusing greatly on chimney height to reduce the indoor pollution. Hence, it is vital to study about the best location and orientation of chimney to maintain IAQ for the safe health of dwellers.

Acknowledgements

The authors are grateful for the ﬁnancial support pro-vided by Center for Rural Technology (CRT), Nepal for conducting this study and the monitoring instrument sup-port provided by Practical Action Nepal (previously Inter-mediate Technology Development Group (ITDG)). Authors would like to acknowledge the local women’ group and staﬀ of CRT for their support during survey and monitoring work. Finally, wholehearted thanks go to all participating households that played their vital role in the research.

References

Akimoto, T., Horikawa, S., Otaka, K., Hayashi, H., Lee, S., 2002. Research on ventilation ceiling system for commercial kitchen. Part 2: ﬁeld measurement of indoor thermal environment and ventilation

performance. Room Vent.

Armendariz Arnez, Cynthia, Edwards, Rufus D., Johnson, Michael, Rosas, I. Arma, Masera, Omar R., Spinosa, F., 2010. Indoor particle size distributions in home with open ﬁres and improved Patsari cook

stoves. Atmos. Environ. 44, 2881–2886.

BalKrishnan, Kalpana, Mehta, Sumi, Kumar, Priti, Ramaswamy, Pad-mavathi, Sambandam, Sankar, Kumar, Kannappa Satish, Smith, Kirk R., 2004. Indoor Air Pollution Associated with Household Fuel Use in India: An Exposure Assessment and Modeling Exercise in Rural Districts of Andhra Pradesh, India. Energy Sector Management Program (UNDP/World Bank) Energy Sector Management Program

(UNDP/World Bank), Washington DC.

Begum, Bilkis A., Paul, Samir K., Dildar Hossain, M., Biswas, Swapan K., Hopke, Philip K., 2009. Indoor air pollution from particulate

matter emissions in diﬀerent households in rural areas of Bangladesh. Build. Environ. 44 (5), 898–903.

Carvalho, Ricardo L., Jensen, Ole Michael, Afshari, Alireza, Bergsoe, Niels C., 2013. Wood burning stoves in low-carbon dwellings. Energy Build. 59, 244–251.

Clark, Maggie L., Reynolds, Stephen J., Burch, James B., Conway, Stuart, Bachand, Annette M., Peel, Jennifer L., 2009. Indoor air pollution, cook stove quality, and housing characteristics in two Honduran

Communities. Environ. Res. 110, 12–18.

Dasgupta, S., Huq, M., Khaliquzzaman, M., Pandey, K., Wheeler, D., 2006. Indoor air quality for poor families: new evidence from

Bangladesh. Indoor Air 16 (6), 426–444.

Davidson, C.I., Lin, S.F., Osborn, J.F., Pandey, M.R., Rasmussen, R.A., Khalil, M.A.K., 1986. Indoor and outdoor air-pollution in the

Himalayas. Environ. Sci. Technol. 20 (6), 561–567.

Dhakal, Shobhakar, 2008. Climate Change and Cities: The Making of a Climate Friendly Future. http://dx.doi.org/10.1016/B978-0-08-045341-5.00007-4, Chapter 7.

Ezzati, Majid, Kammen, Daniel M., 2001. Indoor air pollution from biomass combustion and acute respiratory infections in Kenya: an

exposure – response study. Lancet 358 (9282), 616–624.

Huq, M., Dasgupta, S., Khaliquzzaman, M., Pandey, K., Wheeler, D., 2004. Who suﬀers from indoor air pollution? Evidence from Bangladesh. World Bank Policy Research Working paper 3428. Available online: doi:10.1596/1813-9450-3428.

Kosonen, Risto, Mustakallio, Panu, 2003. Analysis of capture and containment eﬃciency of a ventilated ceiling. Int. J. Ventilation 2 (1), 33–43.http://dx.doi.org/10.1080/14733315.2003.11683651.

MOPE, 2001. Nepal’s State of Environment (Agriculture and Forest).

Ministry of Population and Environment, Kathmandu, Nepal.

Nepal Environmental and Scientiﬁc Services Private limited (NESS), Kathmandu, 1999. Ambient Air Quality monitoring of Kathmandu valley (A report submitted to ADB TA 2847-NEP Project, Ministry of Population and Environment His Majesty’s Government of Nepal). Nepal Health Research Council, 2004. Situation Analysis of Indoor Air

Pollution and Development of Guidelines for Indoor Air Quality Assessment and House Building for Health. Nepal Health Research Council, Ministry of Health, Kathmandu, Nepal. Available online: <http://www.nhrc.org.np>.

Nepal Living Standard Survey (NLSS), 2011/2012. Central Bureau of

Statistics. National Planning Commission Secretariat.

Pandey, M.R., Neupane, R.P., Gautam, A., Shrestha, I.B., 1989. Domestic smoke pollution and acute respiratory infections in a rural community of the hill region of Nepal. Environ. Int. 15 (1–6), 337–340. Practical Action, 2007. Smoke, Health and Household Energy: Research-ing Pathways to ScalResearch-ing Up Sustainable and Eﬀective Kitchen Smoke Alleviation. Practical Action, United Kingdom. Available online:

<

http://practicalaction.org/docs/smoke/smoke_health_household_en-ergy_2.pdf>.

Reid, Holly F., Smith, Kirk R., Sherchand, Bageshwari, 1986. Indoor Smoke exposures from traditional and improved cook stoves compar-isons among rural Nepali women. Mt. Res. Dev. 6 (4), 293–303. Available online: <http://www.jstor.org/stable/3673370>.

Shen, Guofeng, Xue, Miao, Wei, Siye, Chen, Yuanchen, Wang, Bin, Wang, Rong, Shen, Huizhong, Li, Wei, Zhang, Yanyan, Huang, Ye, Chen, Han, Wei, Wen, Zhao, Qiuyue, Li, Bin, Haisuo, Wu, Tao, Shu, 2013. Inﬂuence of fuel mass load, oxygen supply and burning rate on emission factor and size distribution of carbonaceous particulate matter from indoor corn straw burning. J. Environ. Sci. 25 (3), 511– 519.

Singh, Ashish, Tuladhar, Bhushan, Bajracharya, Karuna, Pillarisetti, Ajay, 2012. Assessment of eﬀectiveness of improved cook stoves in reducing indoor air pollution and improving health in Nepal. Energy

Sustainable Dev. 16, 406–414.

Singh, Sudha, Gupta, Gyan Prakash, Kumar, Bablu, Kulshrestha, U.C., 2014. Comparative study of indoor air pollution using traditional and improved cooking stoves in rural households of Northern India.

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Warwick, Hugh, Doig, Alison, 2004. Smoke – The Killer in the Kitchen. Indoor Air Pollution in Developing Countries. ITDG Publishing. Available from <https://practicalaction.org/docs/smoke/itdg% 20smoke%20report.pdf>.

World Health Organization, 2005. Indoor Air Pollution from Solid Fuels and Risk of Low Birth Weight and Stillbirth. WHO Library

Cataloguing-in-Publication Data, Johannesburg.

World Health Organization, 2016. Available online <http://www.who. int/mediacentre/factsheets/fs292/en/>.

You, Yan, Niu, Can, Zhou, Jian, Liu, Yating, Bai, Zhipeng, Zhang, Jiefeng, He, Fei, Zhang, Nan, 2012. Measurement of air exchange rates

in diﬀerent indoor environments using continuous CO2 sensors. J. Environ. Sci. 24 (4), 657–664.