LEVELS AND DETERMINANTS OF INDOOR AIR POLLUTION EXPOSURE IN YOUNG GUATEMALAN CHILDREN

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1 LEVELS AND DETERMINANTS OF INDOOR AIR POLLUTION EXPOSURE IN YOUNG GUATEMALAN CHILDREN N Bruce 1*, J McCracken 2, R Albalak 3, M Schei 4, KR Smith 4 and V Lopez 5 1 Department of Public Health, University of Liverpool, Liverpool, UK 2 Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. 3 Department of International Health, Emory University, Atlanta, GA, USA 4 Environmental Health Sciences, University of California, Berkeley, CA, USA 5 University Rafael Landivar, Quetzaltenango, Guatemala. ABSTRACT Objective: To assess levels and determinants of kitchen pollution and child exposure associated with a range of stove/fuel combinations in rural Guatemala. Methods: 204 households with children <18 months, measurement of 24-hour mean kitchen CO and child CO, and 24-hour kitchen PM 3.5 in sub-sample. Results: Almost 50% homes still used open fires, around 30% chimney stoves (planchas) mostly from a large donor-funded programme. Homes with planchas had lowest kitchen levels: mean (95% CI) CO of 3.09 ( ) ppm vs ( ) for open fires. The same ranking was found for child CO. Multivariate analysis showed stove/fuel type was the most important determinant of kitchen CO (p<0.001), with some effect of kitchen volume and eaves. Stove/fuel type was also the key determinant of child CO (p<0.001), with some effect of child s position during cooking. Conclusion: Community stove programmes have been effective in reducing smoke exposure of young children, but further improvement is needed. INDEX TERMS Developing countries, Biomass fuels, Indoor air pollution, Improved stoves, Children. INTRODUCTION Around two-thirds of the population of developing countries, some 2-3 billion people, still rely predominantly on biofuels (wood, dung and crop residues) for household energy (World Resources Institute, 1998]. Burned in open fires or simple stoves, often indoors, this leads to high levels of air pollution, to which women and young children in particular are exposed (Smith 87, Bruce, 2000). This pollution increases the risk of pneumonia (Smith, 2000), chronic obstructive lung disease and a range of other conditions (Bruce, 2000]. Guatemala is one such country, with large populations of rural people still primarily dependent on wood fuel. Bottled gas (LPG) is used in towns and the larger villages, much less so in rural areas, and where electricity is available its use is generally restricted to lighting. Typical 24 hour average PM 10 levels recorded in Guatemalan homes with open wood fires are µg/m 3 (Naeher, 2000). By contrast, the US Environmental Protection Agency (USEPA) 99 th percentile standards for 24-hour average PM 10 and PM 2.5 concentrations are 150 µg/m 3 and 65 µg/m 3, respectively (USEPA, 1997). Levels of carbon monoxide (CO) in homes using biomass fuels are reported in the range 2-50 ppm for 24 hour averages, and ppm during cooking (Boy, 2002). By comparison, the USEPA 8-hour average CO standard is 9 ppm or 10 mg/m 3. Few studies have attempted to assess population exposure of young children in such settings, or to study the factors that determine the level of exposure. As with * Contact author ngb@liv.ac.uk 566

2 most poor countries, the implementation of interventions to reduce smoke pollution in rural Guatemala have been unsystematic. A variety of improved stoves have been installed through individual purchases by better-off families, and through programmes funded by NGOs, government and external donors. Few of these projects have been evaluated. One recent large-scale programme in Guatemala was led by the FIS (Social Investment Fund), typically installing between 100 and 150 stoves in a community of households. The aim of this study was to assess the pollution levels and childhood exposure in a typical rural setting that had been subject to piecemeal development in terms of household energy. Specific objectives were to investigate (a) the distribution of stove and fuel types in a rural village which had been subject to gradual uptake of improved stoves among better-off families, and a variety of donor-driven stove programmes including the larger scale FIS programme; (b) the levels of kitchen air pollution and exposure of children less than 18 months of age, associated with the different types of stove and fuel; and (c) the influence of other household and behavioural factors on kitchen pollution and children s exposure. METHODS The study site is the village of La Victoria, in the western highlands of Guatemala. In this area, it is common for the mother to carry the child on her back while cooking, usually until months (Engel, 1998). Between , the FIS installed around 100 new stoves in the village. The most commonly used chimney stove, and that installed by the FIS, is the plancha (Figure). The key feature is a metal plate with (usually) three potholes that can be adjusted or closed by adding/removing concentric metal rings (Boy, 2000). A survey was conducted to identify all houses in the village with children less than 18 months, from these a random sample of 250 were selected: 204 (82%) agreed to participate. An interview survey was carried out by five trained bilingual (Spanish and Mam) field workers to assess: stove type, fuel used, time since installation of stoves, smoking (mother and others in the home), lighting, number of rooms, kitchen volume, size of eaves spaces and windows, reported and observed (at the time survey visit made) position of the child during cooking. Measurement of kitchen pollution and child exposure was based on earlier work using CO as a proxy for PM 10 (and PM 2.5 ) (Naeher, 2000), which reported strong associations between 24- hour PM 2.5 and CO. 24 hour kitchen CO was measured using a Gastech 1D passive diffusion tube placed in the kitchen at a height of 1.25 meter, 1m from the fire/stove, at least 1.5 m from doors and windows and, where feasible, at least 1 metre from any wall. This was repeated using identical methods in a random sub-sample of n=29 homes some weeks later to estimate repeatability. PM 3.5 was measured in the same sub-sample (n=24) over the same 24 hour period using an SKC Aircheck Sampler and cyclones with 37 mm diameter Teflon filters, flow rate of 2 liter/minute, co-located with the kitchen CO tubes. This produces a 50% particle cut-off at 3.5 µm. Pumps were programmed to sample 1 minute out of every three, for 24 hours. Filters were pre- and post-weighed at the Department of Analytical Chemistry, University of San Carlos, Guatemala City. CO exposure concentrations were measured using a Gastech 1D tube, placed on the child s clothing on the upper chest. Tubes were read after 24 hours by the field worker. 24 hour child CO measurement was repeated on the sub-sample of 567

3 homes. At interview, mothers were asked where the child was usually located during cooking, and child location during cooking directly observed on two occasions. Field workers were allocated randomly to homes in order to avoid observer bias. Field supervisors validated data from 15% of the homes using direct observation (79%) and repeat assessment (21%). On home visits, observations were made of the position of the tube in the kitchen and on the child. PM 3.5 field quality control included co-located pumps and field blank filters in 3 houses, and validation of the pump flow rate was measured directly using the soap bubble technique. Laboratory procedures included use of blanks and repeat weighing. Data was entered into Epi-Info (Version 6), and this used for all descriptive analysis. Skewed data has been log-transformed where appropriate, although for clarity in presenting levels of pollution and exposure, means (and medians) are given and non-parametric tests used for comparison. Multiple regression was carried out in SPSS. RESULTS Results are reported on 203 of 204 homes with complete data. Almost half of the homes relied exclusively on an open fire, and around 30% on the plancha the majority of which had been installed by the FIS project some 2-3 years previously. 10% used gas (LPG), but in this community, use of a gas stove is usually combined with an open fire, the latter being used for longer cooking tasks and for space heating (this highland area is cold at night, light frosts being not uncommon). The association between 24 hour CO (ppm) and 24 hour PM 3.5 (µg/m 3 ) in the sub-sample of 24 homes, yielded a Pearson correlation of 0.73 (p<0.001). Log transformation effectively normalised the distribution of CO, but not that of PM 3.5 : correlation for log CO and PM 3.5 yielded a similar value of 0.74 (p<0.001). These findings are consistent with the earlier studies. For the 203 homes, log transformation was found to normalise both kitchen and child 24-hour CO. There was a moderately strong association between the log 24 hr kitchen CO and the child CO: Rs (Spearman) = 0.54 (p<0.001). Table 1(a) shows concentrations of 24-hour kitchen CO and child CO for each stove/fuel type. Kitchen concentrations were markedly higher in homes using open fires, compared with those with a plancha (p<0.0001). The lowest mean (and median) was for households purchasing the stove ( Own stove in table). Gas use yielded intermediate concentrations, consistent with concurrent use of open fires for some tasks. These differences are reflected in a consistent way in the 24-hour child CO concentrations. Although also highly significant (p<0.0001), these differences are proportionately less than those for the kitchens. Nevertheless, Table 1(b) shows that even though there is some overlap in the distributions of child CO by stove type, the majority of values for the plancha homes (especially own plancha) are substantially lower than for homes with open fires. Table 1(b) also shows the mean (and median) of the ratios of individual children s personal CO:kitchen CO concentrations by type of fuel/stove, which suggest that the 'cleaner' the stove, the higher the child's 24-hour exposure as a proportion of the kitchen level. Table 1(a). 24 hour C0 levels in kitchen and for child, by stove type. Stove type n = 24 hr Kitchen CO (ppm) 24 hr Child CO (ppm) 203 Median Mean 95% CI Median Mean 95% CI Open Fire FIS plancha Own plancha Gas Other mix p-value* < < * (Kruskall-Wallace test) 568

4 Table 1(b). Distributions of CO (child), and child:kitchen CO ratios, by stove type Stove type n Distributions Child:kitchen CO ratio 25% Median 75% Range SD Mean Median Open Fire FIS plancha Own plancha Gas Other mix PM 3.5 levels measured in the random sub-sample of 24 homes were consistent with the differences in pollution reported in Tables 1(a) and (b). Mean (+ SD) values (µg/m 3 ) of PM 3.5 for open fires (n=11) were 1020 (547), planchas (n=5) 351 (333), and gas/other (n=8) 579 (205). The difference in PM 3.5 between stove types was significant (p=0.023, Kruskall Wallace), and the levels consistent with earlier studies (Naeher 2000, Albalak 2000). Table 2(a) shows the factors associated with (a) log kitchen CO and (b) log child CO, in multiple regression. As log 10 has been used, coefficient values are expressed as the value of 10 beta. Thus for FIS plancha, beta = , so the estimated effect is = 0.424, equivalent to a 58% lower level. For kitchen pollution, the stove type was most important, although there was some evidence of and effect of the size of any eaves space and kitchen volume. Factors with no independent association were window size, number of rooms, observer, and whether other people smoked in the house. Few women in this community smoke. For child CO [Table 2(b)], the stove type and observed position of the child on the two occasions were the most important determinants. For child exposure, the observer appears to have had a significant effect this was not seen for the higher kitchen levels, and is most likely to result from variability in reading the tubes precisely at lower levels. Factors with no independent association were window size, number of rooms, eaves spaces, and whether other people smoked in the house. Table 2(a). Multivariate analysis of determinants of log kitchen 24 hour CO Variable Category Exponentiated coefficient 95% CI p-value Stove type Open fire Reference FIS plancha <0.001 Own plancha <0.001 Gas/fire <0.001 Other <0.001 Eaves space size None Reference Small Large Kitchen vol (m 3 ) DISCUSSION This community survey of a rural Guatemalan village community illustrates the impact of the mixed history of efforts at transition from almost exclusive use of open fires to quite widespread use of improved stoves and some use of cleaner fuels. Nevertheless, almost 50% of homes with young children still used open fires. Of those using improved stoves most were planchas received these through the FIS programme and only a minority (8%) had purchased the stove themselves. Gas is used, rarely exclusively, and just over half use 569

5 electricity for lighting. A key aspect of the methods described here is the use of mean 24-hour CO as a proxy for small particles in the kitchen and exposure of children. The results from the sub-sample of 24 homes confirm this relationship and are consistent with previous studies (Naeher, 2000). Although this association may not be sufficiently tight to predict an individual home or child level, it does appear useful for group means. The use of gas, particularly in combination with open fires, complicates the relationship due to very different ratios of CO:PM emissions with these two types of fuel/stove. Table 2(a). Multivariate analysis of determinants of log child 24 hour CO Variable Category Exponentiated coefficient 95% CI p-value Stove type Open fire Reference FIS plancha <0.001 Own plancha <0.001 Gas/fire Other Observed Kitchen (both) Reference position on Kitchen (one) two occasions Not in kitchen Observer 1 Reference < Kitchen CO levels and measured PM 3.5 (sub-sample) were highest for open fire homes and lowest for the plancha (particularly where obtained by the family) and intermediate for gas, consistent with a recent study in the area (Albalak, 2001]. Young children s exposure assessed by the same two parameters reflected differences in kitchen pollution for each stove/fuel group, although proportionately the differentials were smaller and differences between plancha and gas were minimal. It was interesting that the mean ratios of child:kitchen 24 hour CO increased progressively with less polluting stove/fuel groups. This may reflect protective behavioural responses and aspects of the wider environment in which the child lives. For example, mothers living in more polluted homes may seek to protect their young children from the smoke by keeping them away from it more than in homes with a cleaner atmosphere. There was however no evidence from these data that the observed position of the child differed between stove/fuel types, or by kitchen CO level. Nevertheless, the observed position of the child was associated with the child's exposure level, but without further investigation it is not possible to say whether this is cause or effect. In this setting, these young children move through a range of 'micro-environments' each day, their own kitchen being only one. A child living in a very polluted home will, on balance, encounter less polluted micro-environments when outdoors and visiting other homes, and vice-versa. In a community where around half the homes use open fires and the rest a combination of improved stoves and LPG, there is ample opportunity for mixing. Despite this, the distributions of child CO for planchas and open fires are still quite distinct (Table 1b). Although, as might be expected, physical characteristics of the house such as size of eaves space and kitchen volume influence the kitchen pollution levels, overall these factors were not important in determining children's exposure. The type of stove/fuel, mediated via kitchen pollution levels, was by far the most important factor, with the (observed) location of the child also having some influence. It is possible that the location of the child is a behavioural 570

6 response by the mother wishing to protect her child, but that without further study it is not possible to comment further. Furthermore, the large within-house and within-person variation in exposure found in this study (not reported) will have reduced the statistical power of any analysis of determinants. A larger study and allowance for within-individual variation may well identify modest but important effects of house characteristics on levels of child exposure. CONCLUSION AND IMPLICATIONS 24-hour mean CO concentration offers a simple and useful proxy for particulate pollution levels, at least for groups with cooking stoves in settings where the predominant fuel is biomass and pollution levels are moderately high. In this rural Guatemalan community, kitchen pollution and child exposure with open fires are very high relative to current air quality guidelines. A number of house characteristics, particularly ventilation and kitchen volume, are associated with lower kitchen pollution levels, but improved stoves are by far the most important factor determining kitchen levels and child exposure. The differentials for the children's exposure, though important, were less marked than for kitchen levels probably due to a levelling out of exposures in different micro-environments. These findings support the use of improved stoves programmes as an intermediate step towards cleaner fuels, but also emphasise the importance of more co-ordinated community approach to household energy development. ACKNOWLEDGEMENTS This study was funded by the Department of Child and Adolescent Development, WHO. John McCracken was support by a Fulbright Scholarship. REFERENCES Albalak R, Bruce N, McCracken JP, et al. Indoor respirable particulate matter concentrations from an open fire, improved cookstove, and LPG/open fire combination in a rural Guatemalan community. Environ Sci and Technol, 2001;35: Boy E, Bruce N, Smith KR et al. Fuel efficiency of an improved wood-burning stove in rural Guatemala: implications for health, environment and development. Energy for Sustainable Development 2000:2; Boy E, Bruce N, Delgado H. Birthweight and exposure to kitchen wood smoke during pregnancy. Environ Health Perspect 2002;110: Bruce N, Perez-Padilla R, Albalak R. Indoor air pollution in developing countries: a major environmental and public health challenge. Bull WHO 2000;78: Engel P, Hurtado E, Ruel M. Smoke exposure of women and young children in highland Guatemala: predictions and recall accuracy. Human Organisation 1998;54: Naeher LP, Leaderer BP, Smith KR. Particulate matter and carbon monoxide in highland Guatemala: indoor and outdoor levels from traditional and improved wood stoves and gas stoves. Indoor Air 2000;10: Smith, K. Biofuels, air pollution and health: a global review. Plenum Press, New York, Smith K, Samet J, Romieu I, et al. Indoor air pollution in developing countries and acute respiratory infections in children. Thorax 2000;55: USEPA. Revisions to the National Ambient Air Quality Standards for Particulate Matter. Federal Register July 18, 62(138): WHO - Air quality guidelines for Europe. Tables 4.1 and 4.2 WHO World Resources Institute, UNEP, UNDP, World Bank World Resources: a guide to the global environment. Oxford University Press,