INDOOR AIR POLLUTION AND CHILD ARI: A RANDOMIZED TRIAL

室内空气污染与儿童急性呼吸道感染：随机试验

• 批准号: 6754538
• 负责人: KIRK R SMITH
• 金额: $ 36.41万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-01 至 2005-09-14
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6754538
• 关键词: Guatemala; air pollution; child (0-11); clinical research; disease /disorder proneness /risk; energy source; environmental exposure; environmental health; food processing /preparation; human subject; particle; pollution related respiratory disorder; respiratory infections

DESCRIPTION (Taken from the Investigator's Abstract) The aims are to: 1) conduct the first randomized intervention trial in air pollution history, thus increasing confidence in air pollution risk estimates, which are currently based on observational studies; 2) estimate personal particulate (PM) exposures for children across a wide range of exposures associated with an improved stove (intervention) and the traditional open fire (control) thus potentially assisting efforts to understand the shape of the exposure-response curve of PM impact in young children. After a 7-year search and 14 pilot studies, an excellent site has been characterized in highland Guatemala where PM exposures are dominated by open wood-burning cookstoves producing daily 24-hours PM 2.5 exposure levels of 1000 ug/m3 and higher, i.e., some 60 times more than current United States standards. Such conditions are common in less-developed countries (LDCs), where some two-thirds of households rely on biomass fuels (wood, dung, crop residues). Pilot work has identified a socially and economically acceptable intervention, a chimney stove that is capable of reducing mean exposures by 6- 10x. The primary health outcome to be measured, acute lower respiratory infection (ALRI), is the chief cause of morbidity in children under 5 worldwide and the chief cause of death among LDC children. It thus accounts for nearly 10% of the entire burden of global disease, making it the single largest category of ill-health. The need to examine this relationship in more detail is highlighted by some dozen case-control or cohort studies in the United States and LDCs that have found significant odds ratios for ALRI in young children living in households using wood or other biomass fuels, suggesting that reducing this exposure to pollution may be a powerful preventive intervention. 500 children, allocated randomly to control and intervention groups, will be visited weekly from birth to 18 months to detect a 25% difference in ALRI incidence (power=0.8; alpha=5%). Diagnosis will be done using international protocols and physician verification. Child personal exposures and household microenvironments will be monitored twice each season (four times per year), and more intensely in a subsample. Because pilot studies consistently show passive CO diffusion tubes to be reliable indicators of PM arising from use of wood fuel, they will be used as the primary exposure monitors for the children. Total individual PM exposure will be modeled for each child using the information from the personal CO monitors, from microenvironmental PM and CO measurements in a subsample of households, and activity pattern information for each child. Previous pilot studies at the site have shown that exposures in the intervention and control groups will extend from PM levels similar to those found outdoors in United States cities, where most previous epidemiology has focused, to levels more than an order of magnitude higher. Active smoking risks provide evidence that the curve must become less steep at exposures much higher than ambient air pollution, but it is not known how the curve is shaped in the wide gap between, within which lie the exposures experienced by this study population. An important secondary objective therefore is to describe the relationship between exposure and ALRI incidence across this range. Neither the primary nor secondary aim is likely to be achieved in the United States or other developed country today, because the needed conditions have ceased to exist, i.e., exposures are not dominated by household sources suited to randomized intervention and also lie in a relatively limited range because they are heavily influenced by widespread outdoor sources. Thus, in addition to being directed toward a serious health problem in a large vulnerable population worldwide, this research can assist the worldwide inquiry into PM health effects by moving air pollution epidemiology closer to the strongest stage of the (Bradford) Hill criteria for establishing causality, the "gold standard" of randomized intervention.

描述（摘自研究者摘要） 目的是：1）进行第一次空气中的随机干预试验 污染历史，从而增加对空气污染风险估计的信心， 目前基于观察研究; 2）估计个人 在广泛的暴露范围内，儿童的颗粒物（PM）暴露 与改进的炉子（干预）和传统的明火相关联 （控制），从而可能有助于努力了解的形状， 幼儿PM冲击的响应曲线。 经过7年的搜索和14个试点研究， 在危地马拉高原，PM暴露主要是开放式的， 每天24小时产生的PM2.5暴露水平 1000微克/立方米及以上，即，比现在的美国大约多60倍 标准 这种情况在欠发达国家很常见， 大约三分之二的家庭依赖生物质燃料（木材、粪便、农作物）， 残基）。 试点工作已经确定了一个社会和经济上可以接受的 干预，一个烟囱炉，能够减少平均暴露6- 十倍 待测量的主要健康结局，急性下呼吸道疾病 ALRI感染是5岁以下儿童发病的主要原因 这是全世界最不发达国家儿童死亡的主要原因。 因此， 占全球疾病总负担的近10%， 最大的健康问题。 需要在更多的领域研究这种关系， 细节是由几十个病例对照或队列研究中强调， 美国和最不发达国家发现ALRI的显著优势比， 生活在使用木材或其他生物质燃料的家庭中的幼儿， 这表明，减少对污染的暴露可能是一个强大的， 预防性干预。 将500名儿童随机分配到对照组和干预组， 从出生到18个月每周进行一次访视，以检测ALRI的25%差异 发生率（把握度=0.8; α =5%）。 诊断将使用国际 方案和医生验证。 儿童个人接触和家庭接触 每个季节将监测两次微环境（每年四次）， 并且在子样本中更强烈。 因为试点研究一致表明 被动式CO扩散管是使用 木材燃料，它们将被用作主要的暴露监测器， 孩子 将使用以下公式对每个儿童的个人PM暴露总量进行建模： 来自个人CO监测器的信息，来自微环境PM和 次级抽样家庭的CO测量和活动模式信息 为每个孩子。 以前在该地点进行的试点研究表明， 干预组和对照组的PM水平将从类似于 在美国城市的户外发现，大多数以前的流行病学 集中到一个更高的数量级。 主动吸烟 风险提供的证据表明，曲线必须变得不那么陡峭， 高于环境空气污染，但不知道曲线是如何形成的 在这两者之间的巨大差距中， 研究人群。 因此，一个重要的次要目标是描述 在此范围内暴露与ALRI发病率之间的关系。 无论是首要目标还是次要目标，在美国都不可能实现。 国家或其他发达国家，因为所需的条件 已不复存在，即，暴露不是由适合的家庭来源主导的 随机干预，也在相对有限的范围内， 它们受到广泛的户外来源的严重影响。 因此，此外， 在一个大的弱势群体中被引导到一个严重的健康问题， 这项研究可以帮助全球范围内对PM的调查 通过将空气污染流行病学更接近最强的 阶段的（布拉德福德）希尔标准建立因果关系，“黄金” 标准”的随机干预。