Quantifying the effects of exposure to indoor air pollution from biomass combustion on acute respiratory infections in developing countries

Acute respiratory infections (ARI) are the leading cause of burden of disease worldwide and have been causally linked with exposure to pollutants from domestic biomass fuels in developing countries. We used longitudinal health data coupled with detailed monitoring and estimation of personal exposure from more than 2 years of field measurements in rural Kenya to estimate the exposure-response relationship for particulates < 10 microm diameter (PM(10)) generated from biomass combustion. Acute respiratory infections and acute lower respiratory infections are concave, increasing functions of average daily exposure to PM(10), with the rate of increase declining for exposures above approximately 1,000-2,000 microg/m(3). This first estimation of the exposure-response relationship for the high-exposure levels characteristic of developing countries has immediate and important consequences for international public health policies, energy and combustion research, and technology transfer efforts that affect more than 2 billion people worldwide.     

Indoor air pollution in developing countries

Of the four principal categories of indoor pollution (combustion products, chemicals, radon and biologicals), research in developing countries has focused on combustion-generated pollutants, and principally those from solid-fuel-fired cooking and heating stoves. Such stoves are used in more than half the world's households and have been shown in many locations to produce high indoor concentrations of particulates, carbon monoxide and other combustion-related pollutants. Although the proportion of all such household stoves that are used in poorly ventilated situations is uncertain, the total population exposed to excessive concentrations is potentially high, probably several hundred million. A number of studies were carried out in the 1980s to discover the health effects of such stove exposures. The majority of such studies were done in South Asia in homes burning biomass fuels or in China with coal-burning homes, although a sprinkling of studies examining biomass-burning have been done in Oceania, Latin America and Africa. Of the health effects that might be expected from such exposures, little, if any, work seems to have been done on low birthweight and eye problems, although there are anecdotal accounts making the connection. Decreased lung function has been noted in Nepali women reporting more time spent near the stove as it has for Chinese women using coal stoves as compared to those using gas stoves. Respiratory distress symptoms have been associated with use of smoky fuels in West India, Ladakh and in several Chinese studies among different age groups, some with large population samples. Acute respiratory infection in children, one of the chief causes of infant and childhood mortality, has been associated with Nepali household-smoke exposures. Studies of chronic disease endpoints are difficult because of the need to construct exposure histories over long periods. Nevertheless, chronic obstructive lung disease has been associated with the daily time spent near the stove for Nepali women and found to be elevated among coal-stove users compared to gas-stove users in Shanghai. In contrast to early reports, there seems to be little or no risk of nasopharyngeal cancer from cookstove smoke. Several studies in China, however, have found smoke to be a strong risk factor for lung cancer among non-smoking women. In addition, severe fluorosis has been observed in several parts of China where coal fluoride levels are high.(ABSTRACT TRUNCATED AT 250 WORDS)     

Low-level air pollution and upper respiratory infections in children.

Effects of low-level air pollution were studied in one polluted city and two reference cities in northern Finland by comparing the frequency of upper respiratory infections over a 12-month period in 1982 as reported by parents of children ages 14 through 18 months (n = 679) and 6 years (n = 759). A similar comparison was carried out between children living in the more polluted and less polluted areas of the polluted city. The annual mean and the greatest half-hour concentrations of sulfur dioxide (23 and 807 micrograms/m3), particulates (31 and 291 micrograms/m3), nitrogen oxides (15 and 160 micrograms/m3), and hydrogen sulfide (2 and 177 micrograms/m3) in the polluted city were mainly due to industrial sources. In the reference cities, air pollution was produced mainly by traffic and heating. Adjusted odds ratios (OR) for one or more upper respiratory infections of residents in the polluted city vs those in the reference cities were 2.0 (95% confidence interval [CI] = 1.3-3.2) in the younger age group and 1.6 (95% CI = 1.1-2.1) in the older age group. Within the polluted city, OR calculated for living in more vs less polluted areas were 2.0 (95% CI = 1.0-4.0) in the younger and 1.6 (95% CI = 1.0-2.7) in the older children. The present results suggests that, for children, air pollution can be hazardous in concentrations lower than those recorded in earlier studies from Britain and central Europe. The synergistic effect of sulfur dioxide, particulates, nitrogen oxides, hydrogen sulfide, and other pollutants may be a contributing factor.     

Methodological and quality issues in epidemiological studies of acute lower respiratory infections in children in developing countries

Acute respiratory infections are the most important single cause of global burden of disease in young children globally and a major cause of child mortality. A recent review of studies reporting the incidence of acute lower respiratory infections (ALRI) in young children in the developing world was carried out by the WHO Child Health Epidemiology Reference Group in order to inform global burden of disease estimates. The review highlighted the low number of community-based longitudinal studies of ALRI incidence in young children which met minimum quality criteria. It underscored the need to give attention to issues of study design and the reporting of a basic minimum dataset which describes circumstances under which the studies were being conducted and the key design features of the study which may influence the ALRI estimate. This paper aims to provide methodological guidelines for the design, conduct, and reporting of epidemiological studies of ALRI in under-5s in developing countries. It discusses determinants of study quality related to both study design and statistical analysis and also issues requiring further research. It is hoped that these guidelines will stimulate further work in this field and encourage the publication of reports which contain sufficient data to permit a meaningful meta-analysis of the data, thus forming the basis of more reliable future estimates of global burden of ALRI.     

Indoor air pollution exposure and lower respiratory infections in young Gambian children

In a rural population-based cohort study of approximately 500 Gambian children under five years old followed for one year, incidence of acute lower respiratory infections (ALR) was related to various risk factors including parental smoking and regular carriage on the mother's back while cooking, a proxy measure for exposure to smoke from cooking fires. Two statistical analyses using a 'child-weeks at risk' approach were carried out, including and excluding multiple disease episodes in the same child. Weekly surveillance for ALRI found 75 episodes in 62 children. Stratified analyses using both approaches suggested father's smoking, and, for girls only, carriage on the mother's back while cooking and being part of a polygamous family were the main risk factors associated with infection: when multiple episodes occurring in the same child were excluded, not having a health card was an additional risk factor in children over a year old. Multiple logistic regression modelling of data from both approaches, including each of these risk factors and sex, age, village and season, suggested father's smoking, carriage on the mother's back while cooking and being part of a polygamous family increase risk of ALRI, the latter two for girls only. The analysis excluding multiple episodes in the same child also suggested that not having a health card is a risk factor for children aged 1-5 years. The difficulties in interpreting these findings are discussed.     

The magnitude of mortality from acute respiratory infections in children under 5 years in developing countries.

This article reviews the available evidence of mortality from acute respiratory infections (ARI) among children aged under 5 years in contemporary developing countries and compares the findings with European populations before 1965. In European populations before 1965, the level of mortality was found to be a determinant of the proportion of deaths due to ARI. There were marked differences according to regional patterns of mortality. Deaths from ARI played a smaller role after 1950, when the use of antibiotics became generalized. In developing countries, the role of ARI mortality seems to be similar to the European experience. The age pattern is very marked. In absolute values, ARI mortality is highest in the neonatal period and decreases with age. In relative values, ARI mortality is highest in the postneonatal period. ARI, mainly pneumonia, accounts for about 18% of underlying causes of death in developing countries. Pneumonia and other ARI are frequent complications of measles and pertussis; ARI is also commonly found after other infections and in association with severe malnutrition. Virtually no data are available in developing countries to provide final estimates of the role of ARI in mortality of children aged under 5 years. However, the WHO figure of 1 out of 3 deaths due to--or associated with--ARI may be close to the real range of the ARI-proportional mortality in children of developing countries. Results are discussed in light of the definitions of ARI used in various studies, the difficulties in ascertaining and coding multiple causes of death and the quality of data from some sources.     

The impact of environmental air pollution and incidence of acute respiratory viral infections

The paper characterizes diffuse ambient air pollution (P index) in accordance with the data of Kazan stationary stations in 1996-2000. The incidence of childhood respiratory diseases is studied for the same period. A correlation between morbidity and ambient air pollution is analyzed. There is a direct significance correlation between Kazan's ambient air pollution and morbidity rates in children aged 0-14 years, which is as follows rxy +/- m = 0.626 +/- 0.104. The regression coefficient has been established, which is Ry/x = 0.183 when the atmospheric contamination is changed by one unit.     

Indoor air pollution from unprocessed solid fuels in developing countries

Approximately half of the world's population relies on biomass (primarily wood and agricultural residues) or coal fuels (collectively termed solid fuels) for heating, lighting, and cooking. The incomplete combustion of such materials releases byproducts with well-known adverse health effects, hence increasing the risk of many diseases and death. Among these conditions are acute respiratory infections, chronic obstructive pulmonary disease, heart disease, stroke, lung cancer, cataracts and blindness, tuberculosis, asthma, and adverse pregnancy outcomes. The International Agency for Research on Cancer has classified the indoor combustion of coal emissions as Group 1, a known carcinogen to humans. Indoor air pollution exposure is greatest in individuals who live in rural developing countries. Interventions have been limited and show only mixed results. To reduce the morbidity and mortality from indoor air pollution, countermeasures have to be developed that are practical, efficient, sustainable, and economical with involvement from the government, the commercial sector, and individuals. This review focuses on the contribution of solid fuels to indoor air pollution.     

Indoor air pollution and acute lower respiratory infections in the first two years of life

The relationship between outdoor air pollution and acute respiratory infections (ARI) was previously documented. There are recent indications for connection between indoor air pollution and ARI in infants and young children. The aim of this study was to identify the relationship of indoor air pollutants to acute lower respiratory infection (ALRI) in children (< 2 years). The indoor air pollutants concentrations were measured in the homes of the sample. The sample consisted of 115 children (< 2 years) representing the control group (24), ALRI but no pneumonia (24), pneumonia (30), severe pneumonia or very severe disease (37). Air sampling was performed to measure the concentration of total suspended particulates (TSP), SO2 and CO. These pollutants were found in higher concentrations in cases' homes (52.46 +/- 19.68 microg/m3, 298.15 +/- 669.37 microg/m3, and 1.92 +/- 3.60 ppm) than in controls' homes (31.92 +/- 8.76 microg/m3, not detected, and 0.33 +/- 1.63 ppm respectively). Whereas SO2 was detected only in houses using kerosene, TSP and CO were detected with the different types of cooking fuels. Their mean concentrations were highest for biomass (88.86 +/- 13.30 microg/m3 and 9.29 +/- 2.50 ppm) and lowest for gas (40.78 +/- 15.25 microg/m3 and 0.76 +/- 2.19 ppm). Measures to improve indoor air quality are highly required.     

室外空气污染对儿童呼吸系统健康的影响

目的 探讨空气污染对儿童呼吸系统健康的危害，根据本溪市历年空气质量监测结果，对不同污染区的儿童健康状况进行调查。方法 采取整群抽样方法，在本溪市轻、中、重污染区随机抽取小学和幼儿园各一所，全部幼童为调查对象。结果 本溪市儿童持续咳嗽、咯痰、哮喘、哮喘现患、喘鸣及喘鸣样症状的发生率分别为11．89％，5．44％，1．15％，0．62％，6．98％，5．83％。幼儿呼吸系统各病症发生率均高于学龄儿童的发生率；除幼儿男性持续咳嗽发生率低于女性的发生率外(OR=0．69，95％CI=0．49～0．98)，性别间差异无统计学意义。重、中污染区儿童的发生率高于轻污染区儿童的发生率，其中重污染区儿童喘鸣样症状的发生率高于轻污染区儿童的发生率(OR=1．50，95％CI=1．01～2．25)。沿街居住可使儿童呼吸系统疾病及症状的发生率增高，随着住房与交通干线距离的接近，儿童呼吸系统疾病的发生率也呈现增高趋势。易感因素与室外空气污染的联合作用较强，呼吸系统各种疾病的发生率均以受其他因素影响的易感儿童为高，无其他因素影响的非易感儿童发生率为低。结论 室外空气污染是儿童呼吸系统健康的影响因素。     

Outdoor air pollution and lung cancer

In the 1950s evidence of an ongoing epidemic of lung cancer in the United States and Western Europe led researchers to examine the role of outdoor air pollution, which was considered by some to be a likely cause. Although epidemiologic research quickly identified the central role of cigarette smoking in this epidemic, and despite progress in reducing outdoor air pollution in Western industrialized countries, concerns that ambient air pollution is causing lung cancer have persisted to the present day. This concern is based on the fact that known carcinogens continue to be released into outdoor air from industrial sources, power plants, and motor vehicles, and on a body of epidemiologic research that provides some evidence for an association between outdoor air pollution and lung cancer. This article reviews the epidemiologic evidence for this association and discusses the limitations of current studies for estimating the lung cancer risk in the general population. It also identifies research needs and suggests possible approaches to addressing outstanding questions.     

Understanding household demand for indoor air pollution control in developing countries

More than 2 billion people rely on solid fuels and traditional stoves or open fires for cooking, lighting, and/or heating. Exposure to emissions caused by burning these fuels is believed to be responsible for a significant share of the global burden of disease. To achieve widespread health improvements, interventions that reduce exposures to indoor air pollution will need to be adopted and consistently used by large numbers of households in the developing world. Given that such interventions remain to be adopted by large numbers of these households, much remains to be learned about household demand for interventions designed (in part at least) to reduce indoor air pollution. A general household framework is developed that identifies in detail the determinants of household demand for indoor air pollution interventions, where demand for an intervention is expressed in terms of willingness to pay. Household demand is shown to be a combination of three terms: (1) the direct consumption effect; (2) the child health effect; and (3) the adult health effect. While micro-level data are not available to estimate directly this model, existing data and information are used to estimate just the health effects component of household demand. Based on such existing information, it might be concluded that household demand should seemingly be strong given that willingness to pay, based on existing information, is seemingly large compared to costs for common interventions like improved stoves. Given that household demand is not strong for existing interventions, this analysis shows that more clearly focused research on household demand for interventions is needed if such interventions are going to be demanded (i.e. adopted and used) by large numbers of households throughout the developing world. Four priority areas for future research are: (1) improving information on dose-response relationships between indoor air pollution and various health effects (e.g. increased mortality and morbidity risks); (2) improving information on impacts from interventions in terms of air pollution reductions and also cooking times, fuel use, and heat intensities; (3) improving information on household shadow values for improved health, with separate information for adult and child health; and (4) considering more directly household information, and its adequacy, for their ability to evaluate the relationships between fuel use and health.     

Viral diagnoses using the rapid immunofluorescence technique and epidemiological implications of acute respiratory infections among children in different European countries

From November 1978 to October 1981, a total of 7716 specimens of nasopharyngeal secretions were examined by the rapid immunofluorescence technique to determine the frequency of infections caused by the respiratory syncytial virus (RSV), influenza virus A, and parainfluenza viruses 1 and 3. The tests were carried out in six different virus laboratories located in Newcastle upon Tyne (England), Copenhagen, Oslo, Stockholm, Turku (Finland), and Vienna; laboratories in Lisbon and Paris participated in the study for shorter periods. The specimens were collected from infants and children less than 6 years of age who had been admitted to hospital with an acute respiratory infection. Standardized techniques and quality controlled reagents were used. At least one of the above viruses was detected in 1927 (25%) of the specimens: RSV in 1475, influenza virus A in 123, parainfluenza virus 1 in 110, and parainfluenza virus 3 in 237 specimens. Respiratory syncytial virus dominated in all centres, but in some Scandinavian centres distinct outbreaks due to this virus occurred only once or twice during the 3 years'' study period. Three outbreaks of RSV were observed in Newcastle, but here an unprecedented delay of the first winter''s epidemic occurred. The delay was associated with prolonged school closures in the area, and with a very early outbreak of influenza. Parainfluenza virus 3, which was predominantly a summer virus in Newcastle, was most frequently encountered during the colder months of the year in the other centres.     

广州地区空气污染对儿童呼吸系统疾病就诊人次的影响研究

目的探讨广州地区主要的大气污染物(NO2、PM10和SO2)与儿童呼吸系统疾病门诊人次的关系。方法通过广州市环境保护局和广州某医院分别获得2005年1月1日—2011年12月31日大气污染物(NO2、PM10、SO2)的日均浓度资料和儿科呼吸系统疾病日门诊人次资料,采用分布滞后线性模型分析大气NO2、PM10、SO2对儿科呼吸系统疾病门诊人次的影响。结果大气NO2、PM10和SO2浓度对儿科呼吸系统疾病门诊人次的滞后效应可持续至15 d。大气NO2、PM10、SO2浓度每升高10μg/m3对儿科呼吸系统疾病门诊人次影响的累积效应在0~30 d时均有统计学意义(P0.05),且均于15 d达到最大值(NO2:RR=1.029 2,95%CI:1.024 6~1.033 8;PM10:RR=1.020 4,95%CI:1.016 4~1.024 5;SO2:RR=1.040 8,95%CI:1.032 5~1.049 1)。结论广州大气NO2、PM10、SO2浓度的升高可能会造成15 d内儿童呼吸系统疾病门诊就诊人次的增加。     

Etiology of acute diarrhoea among children in developing countries: a multicentre study in five countries.

A 2-year etiological survey of acute diarrhoea in children aged 0-35 months who were attending treatment facilities was carried out using a standardized protocol in five hospitals in China, India, Mexico, Myanmar, and Pakistan. A total of 3640 cases of diarrhoea and 3279 age- and sex-matched controls were studied; about 60% of the patients were aged less than 1 year and 60% were male. An enteric pathogen was detected in 68% of the cases and in 30% of the controls. In all the study centres, the pathogens most strongly associated with disease were rotavirus (16% of cases, 2% of controls), Shigella spp. (11% of cases, 1% of controls) and enterotoxigenic Escherichia coli (16% of cases, 5% of controls). Rotavirus was commonest among 6-11-month-olds, accounting for 20% of all cases in this age group; 71% of all rotavirus episodes occurred during the first year of life. Shigella spp. were commonest among those aged 12-23 months and 24-35 months, accounting for 22% and 27% of the cases, respectively. The proportion of cases that yielded no pathogen was inversely related to age, being highest (41%) among infants below 6 months of age and lowest (19%) among those aged 24-35 months. These results suggest that microbe-specific intervention strategies for the control of childhood diarrhoeal diseases in developing countries should focus on rotavirus, Shigella spp. and enterotoxigenic E. coli.     

大气污染及对人体健康的影响

大气污染是由来已久的环境问题 ,国内外大量流行病学研究证明大气污染与许多健康效应直接或间接相关 ,可以对人体呼吸系统、心血管系统、免疫功能产生一定的危害 ,造成肺功能下降、心肺疾病门诊量的增加和死亡率的升高。本文综述了近年来国内外有关大气污染对人体健康影响的流行病学研究 ,并提出今后开展此类研究的建议