AN EVALUATION OF THE INDOOR/OUTDOOR AIR POLLUTION AND RESPIRATORY HEALTH OF FARMERS LIVING IN RURAL AREAS OF ANHUI PROVINCE, CHINA X-C Pan 1*, Z Dong 2, L Wang 3 and W Yue 1 1 Dept. of Occupational and Environmental Health, Peking University School of Public health, Beijing, P.R. China 2 Center of Disease Prevention and Control of Bingzhou City, Shandong Province of China 3 Center for Ecological Genetics and Reproductive Health, Peking University ABSTRACT To evaluate the levels of indoor air pollution in rural areas of China and their effects on respiratory health, we monitored the indoor (bedroom and kitchen) and outdoor levels of PM 10, SO 2 and CO in 189 randomly selected households of rural areas, Anhui province, China. We also conducted an investigation of 487 subjects between the ages of 15 65 years old with a questionnaire. The PM 10 level of indoors air was significantly higher than that outdoors (518±27/287±9µg/m 3, P<0.01), in contrast to the SO 2 level that was lower. We didn t find a significant association to asthma onset with these levels of PM 10 and SO 2 of the indoor air (P>0.05). FVC, FEV1 were closely related with the CO and PM 10 exposure indices in the bedroom (P<0.01). Conclusion: the indoor air pollution in rural areas may come from combustion of fuel in cooking and heating, which has had adverse effects on the respiratory health of the subjects. INDEX TERMS Indoor air pollution, PM 10, Rural area, Respiratory health INTRODUCTION The air pollution of China is currently significantly higher than in most of the world, but it does not appear that outdoor air pollution is a major risk factor for human health. Nowadays most people living in urban areas spend the greater part of their time indoors, where concentrations of many air pollutants are higher than outdoors (Carrer et al., 1997). In fact, exposure to indoor air pollutants may play an important role in affecting the health of the human body. (Infante-Rivard, 1993). Many studies suggest that conditions of poor indoor air quality, such as inadequate ventilation, uncomfortable microclimate or irritant air pollutants, may play an important role as adjuvant factors in the development of various respiratory symptoms. (Viegi et al., 1991). Similar studies in China have scarcely counted indoor air pollution as important and mainly focus on the health effects of ambient air pollution from urban areas, traffic exhaust and occupational exposure. Now, more than 70 percent of China s populations also live in rural areas and some of them have quite poor living conditions, where respiratory diseases are the leading cause of death. The exposure-response relationships at concentrations of hundreds of µg/m 3, which are typical of indoor environments in some developing countries (e.g. China), are relatively unknown, so we need to assess this relation at exposure levels typical of these * Contact author email: xcpan@bjmu.edu.cn 982
settings. Research on the health effects of indoor air pollution in developing countries has been hindered by lack of detailed data about exposure and illness outcomes. In the present study we directly examined the exposure-response relationship between indoor/outdoor air pollution and respiratory symptoms/lung functions in a field study in rural areas of southeast China. METHODS Participants The study field was located in rural areas of four counties, Anhui province of China. It covered more than 30 small towns of this area, consisting of lake, plain, and hill and mountain areas. 189 households (62 from the lake area, 74 from the plains and 53 from the mountain area) were selected randomly to represent various geographic and socioeconomic background of this area. They had similar tribal backgrounds, living habits, and diet. At the same time, about 500 individuals aged from 15 65 yr. from the study households were by interviewed by questionnaire for their respiratory health conditions. Exposure We did the research in the winter of 1999. The level of sulphur dioxide (SO 2 ) particles smaller than 10µm in diameterpm 10 and carbon monoxide (CO) indoors were selected as the index of indoor air pollution for the study. We monitored the level of these pollutants in the bedrooms, kitchens, yards and the farmlands of the study households in real time twice a day for two weeks. A Dust-Trak air monitor (Model 8520, TSI Inc.) was used to measure in real time PM 10 concentrations in both indoor and outdoor air, respectively. A portable Infrared monitor (Model 8551,TSI Inc.) was used to monitor the indoor and outdoor CO concentrations, temperature and relative humidity (Schnell RC, 1992). We measured the pollution in actual conditions of use and simultaneously recorded the location and activities of all the household members especially activities such as cooking time that would affect exposure to pollution. We also interviewed household members about household energy use technology and their time-activity patterns. We estimated profiles of exposure for every subject, which accounted for daily and day-to-day variability of exposure and time activity pattern. Health The health questionnaire was based on that of the British Medical Respiratory Committee and revised according to the different status of the study field. It consisted of age, gender, education, occupation, and general health status, living habits, exposure to indoor microenvironment factors, cooking, and smoking, respiratory symptoms and other daily activities. The trained students of a medical college conducted the health survey with the questionnaire by face-to-face interview. Determination and Data analysis The determination of levels of PM 10, SO 2 and CO was taken with standardized procedures. The t-test and X-square test were used for estimates of variances of the pollutants level. Effect size of various factors for respiratory symptoms and lung function were estimated with two models. First, is a linear model with an ordinary least-squares regression of symptoms rates. We accounted for clustering of observations in units of Household. Second, we used a logistic probability model y=f (X β+u): y, X, andβare defined as in the linear model; F=cumulative logistic distribution, F (z)=exp (z) divided by [1+exp (z)]. Because the data for level of indoor air pollution was all belong to un-normal distribution, all data on level of indoor air pollutants 983
were analyzed after transforming it into logarithms and showed with geometric mean ± standard deviations. RESULTS 1. General situation for the study group Table 1 contains demographic information for individuals from the 189 study households. It shows that the study group had a similar sex ratio and age, but the education level for the women was significantly much lower then that of the men (P<0.001). Smoking rates for the men were much higher then for the women (P<0.01). Table 1. Demographic information of study group Male Female Total Sex 246 221 467 Mean (SD) Age 35.67±13.70 36.58±12.84 36.12±12.62 Education (years) 6.73±3.4 2.71±3.8 5.06±4.4 No. Of smoking 134 11 145 2. The level of indoor/outdoor air pollution and character of exposure in rural area Table.2 contains the level of PM 10, SO 2 and CO in indoor air (bedrooms and kitchens) and outdoor air (yard/farmland). It shows that the level of PM 10 in kitchens was significantly higher then that in bedrooms (P<0.01), implying an association with cooking. The trend of PM 10 levels is in the rural areas is as follows: Kitchen > Bedroom > Yard > Farmland The levels of SO2 and CO were not different significantly between indoors and outdoors. It suggested that PM 10 was a chief indoor air pollutant in rural areas of China. Table 2. The level of PM 10, SO 2 &CO indoors/outdoors (Mean±SD) Kitchen Bedroom Yard Farmland N 373 504 366 55 PM 10 (µg/m 3 ) 518±27* 340±9 287±9 270±10 SO 2 (µg/m 3 ) 12.4±36 10.9±18 11.0±19 10.8±18 CO (mg/m 3 ) 2.0±9.9 1.62±6.0 1.62±4.5 2.0±4.5# *(t-test, P<0.01, kitchen/bedroom) #t-test, P<0.01farmland/yard In the study area, about 80% of the households used only biofuel (wood, charcoal and agricultural residues) and used traditional stoves, which have high emission rates. Most of the households under survey cook three meals per day, of the biofuel users 91% in separate kitchens inside the house, 19% used them in separate kitchens outside the house. The average cooking period in the sample was about two hours. Table.3 shows the level of indoor air pollutants (PM 10, SO 2, CO) at cooking/non-cooking time in kitchens. The results demonstrate that the level of PM 10 was 3-4 times higher during cooking then that during non-cooking time, reaching 40,000µg/m 3 and for CO, the level showed a similar trend. Table 3. Level of indoor air pollutants during cooking and non-cooking time Cooking Non-cooking P N 123 228 - PM 10 (µg/m 3 ) 1251±39.2 332±10 <0.001 SO 2 (µg/m 3 ) 13.9±49.4 11.8±33 0.26 CO (mg/m 3 ) 3.0±2.1 1.62±5.5 <0.001 (T-test) 984
In order to assess accurately the level of exposure to indoor air pollution, we investigated and recorded the types and times of daily activities of study subjects (time-use patterns), estimating the exposure level to indoor air pollutants combined with the measured concentration (see Table 4). The results showed that the time the women stayed in the kitchen and bedroom was significantly longer then the men (P<0.01); the time they stayed outdoors was not much different. We have also shown in this table that the farmers in this area everyday spent more than 60% of their time indoors such that for the peoples of rural areas, the indoor air quality appears to play an important role in their health. Table 4. the daily time-activity patterns for the subjectshours Male Female t-test P N 245 222 - - Bedroom (χ±s) 9.59±4.09 10.56±3.59 2.72 <0.01 Kitchen (χ±s) 1.36±2.15 3.78±2.48 11.2 <0.01 Yard (χ±s) 2.44±2.51 2.69±2.16 1.15 0.25 Farmland (χ±s) 0.84±2.66 0.62±1.49 1.10 0.27 Others (χ±s) 8.87±6.12 5.07±6.06 6.71 <0.01 3. Exposure-response relation between respiratory health and indoor air pollution Table 5 shows the results of our Logistic regression analysis for various factors related to respiratory symptoms (asthma, cough, expectoration) of the study subjects. It reveals that warming with the charcoal stove was associated with asthma attack (P<0.001). The frequency of exposure to pesticides had a positive correlation to expectoration; cleaning indoors was negatively associated with cough (P<0.01). Table 5. the factors associated with asthma, cough and expectoration significantly (Logistic model) Symptoms Variables OR 95% CI P Asthma attack Exposure to pesticides 1.13 0.981.03 0.06 Warming with the charcoal stove 2.85 1.615.03 <0.001 Expectoration Exposure to pesticides 1.19 1.041.37 0.01 Cough Cleaning indoors 0.41 0.190.87 0.02 (N467) The change of lung function is an important index for the health effects of indoor air pollutants. We took multiple measures of the concentration and time of exposure as indices of exposure, analyzing their association with lung function by Logistic regression models (see Table 6). Table 6. Regression coefficient ( 1000)between Indoors/outdoors exposure indices to PM 10 and the lung function(fvc,fev1, FEV1%) Place FVC (n=324) FEV1 (n=325) FEV1% (n=324) Bedroom -11±6-25±7** -6±1** Kitchen -4±6-2±7-0.5±1 Yard 11±27-2±6 Farmland -37±42-38±48-3±8 985
FVC: forced vital capacity; FEV1: forced expiratory volume in first second FEV1%: percentage of forced expiratory volume in first second to forced vital capacity **: (P<0.01) Table6 shows that after adjusting for some confounding factors (e.g. sex, asthma and smoking), exposure indices to PM 10 in the bedroom had a negative correlation to the level of FEV1 and FEV1% of study subjects (P<0.01). It suggested that exposure to PM 10 indoors has adverse effects on the lung function of the subjects. Table 7 shows that exposure indices to CO in bedrooms also had a negative correlation to the level of FEV1 and FEV1% of study subjects (P<0.01). Table7. Regression coefficient ( 1000)between Indoors/outdoors exposure indices to CO and the lung function(fvc, FEV1, FEV1%) Places FVC (L)(n=314) FEV1 (L) (n=314) FEV1% (n=314) Bedroom -5±2** -7±2** -1.1±0.3** Kitchen -0.4±1.3-0.8±1.4-0.14±0.26 Yard 5±9 4±10-0.04±1.8 Farmland -9±8-12±9 1.3±1.7 The results of Logistic regression analysis also revealed that the concentration of indoors air pollutants were not significantly associated with lung functions (P<0.05). DISCUSSION Indoor air pollution in the rural areas and its character Recently in China, more studies concern the relations between urban indoor air pollution and health effects, but there are scarcely any studies about adverse effects of indoor air pollution in less developed rural areas. The results of our study suggest that there is quite serious indoor air pollution in the households of rural areas, with about one third of the bedrooms of the subjects having levels of more than 450µg/m 3 of PM 10. Because most of the households used only biofuels (fuel wood, charcoal and agricultural residues) for cooking and warming the households and no difference has been found about the SO 2 pollution level between the indoor and the outdoor, so it is considered that the PM 10 was the major indoor air pollutant in this rural area. The results also revealed that the indoor air pollution in rural areas of China might mainly come from cooking in the kitchen. The trend of the pollution was as follows: kitchen > bedroom > courtyard. The relations between the indoor air pollution in the rural areas and the human health Recent epidemiological studies have demonstrated that increased exposure to PM 10 can increase the frequency of respiratory diseases such as asthma, and decrease the pulmonary function of the people. Our study has found that exposure indices to PM 10 in bedrooms were negatively associated with the level of FEV1 and FVC/FEV1 of study subjects (P<0.01), which is consistent with studies of rural communities in the USA (McCurdy SA, 1996). This study also found a significant positive correlation between chronic cough and the frequency of exposure to pesticides (p<0.01). The results revealed that life style and many exposure factors in rural areas are very different from that of the urban areas, which need further research in the future. Many studies reported that short-term exposure to MP 10 could damage the lung 986
function, e.g. the vital capacity (Pope CA, et al. 1993), but it was not found in our study that the significant correlation between the lung function and the level of exposure to PM 10 in the kitchen. CONCLUSION We consider that the one cause of the indoor air pollution in the rural areas comes from the combustion of fuel in cooking and warming. There was a positive association between the level of indoor air pollution and the respiratory health of the human body. REFERENCES Carrer P, Alcini D, Cavallo D et al. 1997. Daily personal exposure to air pollutants of office workers in Milano. In: Proceedings of Healthy Buildings IAQ 97, Woods JE, Grimsrud DT, Boschi N, eds. Washington: pp.249-254. Infante-Rivard C. 1993. Childhood asthma and indoor environmental risk factors. Am J Epidemiol. Vol.137: 834-844. McCurdy SA. 1996. Respiratory health of California rice farmers. American J of Respiratory Critical Care Medicine. Vol. 153(3): 1553-1559. Pope CA. 1993. Acute effects of PM 10 pollution on pulmonary function of smoker with mild to moderate chronic obstructive pulmonary disease. American Review Respiratory Diseases. Vol. 147: 1336-1440. Schnell RC, Allen GA, Hansen ADA. Black carbon aerosol output from a photocopier. Presentation at the 85th Annual Meeting & Exhibition Air & Waste Management Association, Kansas City, MO, June 21 26, 1992. Viegi G, Carrozzi L, Paoletti P et al. 1991.Effect of some indoor environmental factors on respiratory symptoms and lung function in a sample of young nonsmokers in North Italy. Aerobiologia. Vol.7: 152-159. 987