Air pollution triggers more heart attacks than using cocaine and poses as high a risk of sparking a heart attack as alcohol, cof

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问题     Air pollution triggers more heart attacks than using cocaine and poses as high a risk of sparking a heart attack as alcohol, coffee and physical exertion, scientists said on Thursday. Anger, marijuana(大麻)use and chest or respiratory(与呼吸有关的)infections can also trigger heart attacks to different extents, the researchers said, but air pollution, particularly in heavy traffic, is the major culprit(问题的起因).
    The findings, published in The Lancet journal, suggest population-wide factors like polluted air should be taken more seriously when looking at heart risks, and should be put into context beside higher but relatively rarer risks like drug use. Tim Nawrot of Hasselt University in Belgium, who led the study, said he hoped his findings would also encourage doctors to think more often about population level risks. "Physicians are always looking at individual patients—and low risk factors might not look important at an individual level, but if they are prevalent in the population then they have a greater public health relevance," he said in a telephone interview.
    Nawrot’s team combined data from 36 separate studies and calculated the relative risk posed by a series of heart attack triggers and their population-attributable fraction(PAF)—in other words the proportion of total heart attacks estimated to have been caused by each trigger. "Of the triggers for heart attack studied, cocaine is the most likely to trigger an event in an individual, but traffic has the greatest population effect as more people are exposed to(it)," the researchers wrote. "PAFs give a measure of how much disease would be avoided if the risk was no longer present."
    A report published late last year found that air pollution in many major cities in Asia exceeds the WHO’s air quality guidelines and that toxic cocktails of pollutants results in more than 530 000 premature deaths a year. While passive smoking was not included in this study, Nawrot said the effects of second-hand smoke were likely to be similar to that of outdoor air pollution, and noted previous research found that bans on smoking in public places have significantly reduced heart attack rates.
    Tim Chico, a heart specialist at the University of Sheffield who was not involved in this research, said it would help health authorities focus on the most important triggers. "However, what triggers the heart attack should be considered the ’ last straw.’ The foundations of heart disease that lead to a heart attack are laid down over many years," he said in an e-mailed comment. "If someone wants to avoid a heart attack they should focus on not smoking, exercising, eating a healthy diet and maintaining their ideal weight. "
What do we know about PAFs?

选项 A、They’re the proportion of the death related to heart attacks.
B、They reveal that cocaine has the greatest population effect.
C、They measure the amount of disease we could avoid without the trigger.
D、They’re based on data collected from more than 36 doctors.

答案C

解析 事实细节题。本段主要讲述研究的内容,引出了人群归因危险度百分率。这一概念可以衡量如果没有致病因素,我们可以避免的疾病数量,因此答案为C)。
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