Indoor and Outdoor Air Pollution in the Himalayas Cliff I. Davldson," Shaw-Feng Lln, and James F. Osborn
Departments of Civil Engineering, Biomedical Engineering, and Engineering & Public Policy, Carnegie-Mellon University, Pittsburgh, Pennsylvanla 152 13 M. R. Pandey
Department of Medicine, Bir Hospital, Katmandu, Nepal R. A. Rasmussen and M. A. K. Khaill
Department of Environmental Science, Oregon Graduate Center, Beaverton, Oregon 97006
rn Air pollutant concentrations, have been measured in residences in the Himalayas of Nepal where biomass fuels are used for cooking and heating. Levels of total suspended particles are in the range 3-42 mg/m3, with respirable suspended particles in the range 1-14 mg/m3 in the houses sampled. High concentrations of several trace elements have also been measured. Limited data for gaseous species show appreciable levels of carbon monoxide, carbon dioxide, methane, and several non-methane hydrocarbons. A questionnaire concerning energy use administered in each household suggests that high per capita use of biomass fuels is responsible for the excessive pollutant concentrations. Application of a one-compartment mass balance model to these houses shows only rough agreement between calculated and measured values, due to uncertainties in model input parameters as well as difficulties in estimating average pollutant concentrations throughout each house. High outdoor concentrations of potassium and methyl chloride, previously shown to be tracers of biomass combustion, indicate that the indoor biomass combustion also degrades the outdoor environment. Values of crustal enrichment factors for trace elements in the air and snow of the region suggest that the polluted air is generally confined to the populated villages, with more pristine air at higher elevations.
Introduction Air pollution is generally considered a problem of industrialized societies. Exhausts from motor vehicles, coal and oil-fired boilers, manufacturing operations, and other industrial sources have been monitored extensively in developed countries. The physical and chemical forms of pollutants emitted from these sources have been studied in detail. Recent research efforts in North America and Europe have included indoor as well as outdoor environments. This research has shown that pollutants emitted from building materials, consumer products, fobacco, and appliances using gas or kerosene may degrade air quality in residences and other buildings. Exposure to pollutants indoors may pose a greater health risk than exposure outdoors: individuals typically spend about 80-90 90 of 0013-936X/86/0920-0561$01.50/0
their time indoors, and peak concentrations of some pollutants in buildings often exceed ambient levels (I). In contrast to the wealth of data generated in industrialized countries, there have been few studies of air pollution in developing areas of the world. Of particular concern is the paucity of information on pollutants emitted from combustion of biomass fuels. Roughly half of the world's households cook daily with wood, crop residues, or animal dung used in simple stoves made of rock or clay. Most of these households are in rural areas of South America, Africa, and Asia (2). Emissions from these stoves can be significant (3), yet our current understanding of the pollutants and associated human exposures is extremely limited. In this study, we report concentrations of several pollutants in Himalayan villages, where biomass combustion is the main source of energy. Nepal was chosen for the research because of its high altitude: cold temperatures through much of the year require fires that burn over extended periods for space heating. Human exposure to the pollutants is also likely to be greatest at high altitudes because of the large fraction of time spent indoors. In addition, we examined the influence of indoor biomass combustion on outdoor pollutant concentrations in the Himalayas. Industrial activities were minimal in the rural regions sampled; hence, the stoves were expected to be a dominant source of ambient air pollution. Finally, we compared indoor and outdoor pollutant levels in rural areas of Nepal with those in Katmandu, the capital city (population 420 000, 1981 census). Combustion of fossil fuels, particularly leaded gasoline, is significant in the city. This study has been designed to assist the chronic bronchitis and domestic air pollution sampling program, supported by the National Council for Science and Technology in Nepal and the Mrigendra Medical Trust ( 4 ) .
Experimental Methods Indoor sampling for a variety of pollutants was conducted in 18 houses in several Nepali villages, while outdoor sampling took place at Hotel Everest View and in Katmandu (Figure 1). None of the villages contained industries. Alapot, Bhadrabas, and Sundarijal had infre-
0 1986 American Chemical Soclety
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100 h m
Figure 1. Locations of sampling in Nepal for a variety of pollutants.
quent motor vehicle traffic and limited electrical service; the total population of these three villages was less than 1000. The high altitude locations were at least 75 km from the nearest road and had no electricity. The populations of Lukla, Phakding, Namche Bazar, and Kumjung were 150, 60, 900, and 1300, respectively. All of the experiments were conducted during December 1982-January 1983, when clear, cold weather characterized the Himalayas. Outdoor temperatures averaged -10 OC at the high elevations but reached +10 "C in Katmandu Valley. Indoor particulate samples were collected with PTFE Teflon filters (Gelman Sciences type TF, 2 pm pore size, 37-mm diameter) positioned 0.7 m above and 1m from the stove. This location was chosen to simulate the exposure of an individual cooking or tending the fire. Sampling lasted 1-2 h during stove operation. Two filters were used simultaneously in 17 of the houses: one with a cyclone (5) for sampling respirable suspended particles (RSP, aerodynamic particle diameter less than 4 pm) and the other without a cyclone to collect total suspended particles (TSP). Characteristics of the sampling inlet probably excluded particles greater than 10-20 pm aerodynamic diameter (6). One additional house included sampling for TSP only. All of the Teflon filters were analyzed gravimetrically and for 12 trace elements. Tissuquartz filters (Pallflex QA02500,47-mm diameter) were used in the two houses in Kumjung to sample sulfate, nitrate, and carbon. Sampling was simultaneous with that of the Teflon fiiters. Flow rates for all of the indoor Teflon and Tissuquartz filters averaged 2 L/min at standard temperature and pressure (STP). The collection efficiency for both types of filters at this flow rate is over 90%, even for submicron particles (7). Carbon monoxide (CO) was measured at several locations in each of the two Kumjung houses, using an Ecolyzer 7000. In addition, samples of air inside and outside of one house in Sundarijal were collected in stainless steel cylinders for measurement of several trace gases (8, 9). For each house sampled, physical characteristics of the stove and of the house were noted. The woman responsible for operation of the stove was interviewed with respect to stove use patterns, fuel types, attitudes toward the smoke, and health problems. The questionnaire designed by Smith (10) and administered previously in India was used. Outdoor sampling at Hotel Everest View included three exposure periods with Nuclepore polyester filters (0.8 pm pore size, 20 x 25 cm) for analysis of trace elements and two exposure periods with 47-mm diameter Tissuquartz filters for analysis of sulfate, nitrate, and carbon. A Sierra 235 impactor with Nuclepore backup filter was used on one occasion to obtain trace element size distribution data. Nuclepore filter media was chosen for outdoor trace element sampling due to ease of digestion for large filters, as 562
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well as low blank values (11) and satisfactory collection efficiencies (12). These exposure periods varied from 11 to 43 h during a 4-day period. Flow rates for the trace element sampling runs averaged 90 L/min STP, while flow rates for the sulfate, nitrate, and carbon sampling averaged 3 L/min STP. To obtain information on contaminants in the air far above the villages, samples of surface snow from a storm a few days earlier were collected with 1-L polyethylene bottles several hundred meters from the Hotel. The snow was kept frozen from the time of collection until digestion, with the exception of several days during shipment home. Outdoor sampling in Katmandu was conducted in a hotel courtyard 10 m above the ground and 100 m from the nearest road. Teflon filters (37-mm diameter), and Tissuquartz and Nuclepore filters (47-mm diameter), were used during overlapping time periods. Sampling included two filters of each type for periods averaging 18 h. An additional Nuclepore filter was used for sampling 2 m above ground at the curb of a busy city street, for a period of 7 h during the day. Flow rates varied from 3 to 8 L/min STP for these filters. Carbon monoxide was monitored at the courtyard location over a period of 3 days. The filter, impactor, and snow samples were digested in clean laboratories at Carnegie-Mellon University (CMU) following procedures summarized elsewhere (11,13, 14). Analyses for trace elements by atomic absorption spectrophotometry and for sulfate and nitrate by ion chromatography were conducted at C-MU. Analysis of the Tissuquartz filters for carbon by an optical-thermal method (15) was conducted at Oregon Graduate Center (OGC). Preparation of the stainless steel cylinders for measurement of trace gases, and analysis by gas chromatography, also took place at OGC (8,9). Samples collected in the present study were included in quality assurance and interlaboratory comparison programs described elsewhere (11, 13, 14).
Results and Discussion Indoor Air Pollution. Table I summarizes results of the survey. Physical descriptions of the Nepali houses, and characteristics of the families and their lifestyles, are generally similar to those in rural areas of other developing countries (IO,16,17). Energy consumption patterns are quite different, however: stove use for cooking and heating in the Nepali households averages 11.6 h/day, with additional use of a fireplace in many instances. In comparison, stove use for cooking throughout the developing world is estimated at 2.9 h/day (16), mostly in regions where heating needs are minimal. Several of the respondents in the current study indicated continuous stove operation during daylight hours for heating; four households had fires burning 24 h/day. Wood was the principal fuel, with lesser amounts of animal dung, charcoal, and crop residues. Charcoal emits less particulate matter and burns more efficiently than the other biomass fuels (16), but its expense prevented widespread use in the Nepali households (open market prices in US.dollars: charcoal $0.16/kg, wood 0.08/kg, and dung O.O4/kg according to our survey). In all of the houses studied, the stoves were made of dried mud, typically 0.75 m on a slide (total volume 0.4 m3) with an opening 0.2 m X 0.2 m in the front for inserting fuel. None of the houses had chimneys, although many had small holes in the roof above the stove to provide some ventilation. The information in Table I suggests serious energy supply problems in the villages studied. On the basis of the original data, the per capita biomass fuel use averages 8.2 kg/day at high elevations and 2.8 kg/day in the lower
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Table I. Results of the Questionnaire Administered in 18 Rural Nepali Householdsn arithmetic av SD
Table 11. Airborne Concentrations of Particulate Mass and Several Chemical Species at Indoor and Outdoor Locations in Nepala indoor concn, NTsp= 18 and NRsp= 17
range
7.7 3.0 2-13 no, of family members living in the house 3700 1600 2000-6200 annual family incomebj 46 16 21-75 age of cook, years 13 2.0 10-17 age women in family began to cook, years 95 10-270 100 age of house: years 8600 6600 1900-19000 value of house' 1-10 3.4 2.2 no. of rooms 94 60-400 190 volume of house, m3 daily stove use 1.6 2-8 4.6 cooking, h 6.7 0-20 7.0 other," h 6.6 0.5-24 10 daily fireplace use: h 34 5-120 47 daily fuel use!. kg 3.5 3-16 7.7 daily fuel gathering," person-h 1.2-5.5 3.0 1.3 fuel burn rate,' kg/h
"The stove, fireplace, and fuel wood data refer to the winter season; slightly smaller values apply to summer. Nearly all of the houses were two stories. Houses at the low elevations generally included a large living room and small kitchen on the first floor, with separate bedrooms upstairs. Houses at the high elevations had an animal stable as the first floor, and a single large room (plus a small chapel in some cases) upstairs for the occupants. In almost all instances, respondents indicated that they were at or near the stove more than half the time during stove use. Virtually all expressed a strong dislike of the smoke, with most reporting chronic coughing and eye irritation. Incomes for families at high elevations only. All families at the low elevations reported a subsistence lifestyle. CExcludingthe houses in Lukla and Phakding which were 1 and 4 years old, respectively. dSpace heating, warming bath water, preparing animal fodder. eFor the eight houses having fireplaces. /Daily stove use for cooking was virtually identical at low and high elevations. Daily stove use for other purposes (mainly space heating) averaged 3.4 and 9.7 h/day at low and high elevations, respectively. Total daily fuel use averaged 26 and 63 kg/day, respectively. BIn decreasing order by frequency of use: pine, rhododendron, fir, birch, cedar, juniper. Lesser amounts of crop residues (wheat, soybean, corn, sorghum), animal dung, and charcoal are included in these values. hData obtained at high elevation only. Families at low elevation bartered for or purchased some of their fuel, in addition to collecting it themselves. 'Based on daily fuel use (kg/day) divided by stove and fireplace use (h/day) for each house. Average burn rates at low and high elevations were nearly identical. jIn U S . dollars.
elevation villages, compared with 1.9 kg/day in rural areas of India (17). Furthermore, the table shows that high elevation families spend an average of 7.7 person-hours per day collecting the fuel. Rural families at lower altitudes in Nepal and India typically spend 0.5 person-hours per day at this task (16). Nearly all respondents in our survey reported greater distances traveled to reach the fuel and longer times to collect it in recent years. Informal interviews conducted with several additional residents of these villages indicated that the biomass fuel shortages are ubiquitous throughout this area of the Himalayas. The biomass energy crisis throughout the developing world (18) is apparently severe in Nepal. Table I1 summarizes airborne particle data obtained at indoor and outdoor locations. Concentrations of TSP and RSP mass, trace elements, Sod2-,NO3-, and C are given. The trace elements are categorized as crustal or enriched, depending on the value of the crustal enrichment factor (19). Crustal composition data have been taken from Taylor (20). The crustal elements in Table I1 all have enrichment factors < 10 (with the exception of indoor RSP for K, discussed below), while the enriched elements have values > 10. These enrichments are consistent with other
outdoor concn Hotel Everest Katmandu, View, N = 3 N = 4 280 (1.2)
mass
TSP 8800 (1.8Ie RSP 4700 (1.9Id
A1
TSP RSP TSP RSP TSP RSP TSP RSP TSP RSP TSP RSP TSP RSP
33 (3.1) 2.8 (3.0) 45 (2.7) 3.4 (2.7) 62 (4.1) 8.3 (2.8) 64 (3.1) 32 (2.9) 11 (4.1) 0.78 (2.6) 2.7 (3.3) 0.21 (2.3) 3.7 (2.6) 0.62 (4.5)
TSP RSP TSP RSP TSP RSP TSP RSP TSP
