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Children attending schools located in high-traffic zones have a 45 percent increased risk of developing asthma, even though time

admin2011-03-11  46
问题     Children attending schools located in high-traffic zones have a 45 percent increased risk of developing asthma, even though time spent at school only accounts for about one-third of a child’s waking hours, according to new research.
    Asthma is the most common chronic childhood illness in developed countries and has been linked to environmental factors such as traffic-related air pollution. "While residential traffic-related pollution has been associated with asthma, there has been little study of the effects of traffic exposure at school on new onset asthma," says Rob McConnell, professor of preventive medicine at USC’s Keck School of Medicine. "Exposure to pollution at locations other than home, especially where children spend a large portion of their day and may engage in physical activity, appears to influence asthma risk as well."
    The study appears online in the journal Environmental Health Perspectives. The study drew upon data from the Children’s Health Study (CHS), a longitudinal study of children in Southern California communities that was designed to investigate the chronic effects of air pollution on respiratory health. Using a cohort of 2 497 kindergarten and first grade children who were asthma-free when they entered the study, researchers examined the relationship of local traffic around schools and homes to diagnosis new onset asthma that occurred during three years of follow-up. Traffic-related pollution exposure was assessed based on a model that took into account traffic volume, distance to major roadways from home and school and local weather conditions.
    Regional ambient ozone, nitrogen dioxide (二氧化氮) and particulate matter were measured continuously at one central site in each of the 13 study communities. The design allowed investigators to examine the joint effects of local traffic-related pollution exposure at school and at home and of regional pollution exposure affecting the entire community. Researchers found 120 cases of new asthma. The risk associated with traffic-related pollution exposure at schools was almost as high as for residential exposure, and combined exposure accounting for time spent at home and at school had a slightly larger effect. Although children spend less time at school than at home, physical education, and other activities that take place at school may increase ventilation rates and the dose of pollutants getting into the lungs, McConnell notes. Traffic-related pollutant levels may also be higher during the morning hours when children are arriving at school.
    Despite a state law that prohibits school districts from building campuses within 500 feet of a freeway, many Southern California schools are located near high-traffic areas, including busy surface streets.
    "It’s important to understand how these micro-environments where children spent a lot of their time outside of the home are impacting their health," McConnell says. "Policies that reduce exposure to high-traffic environments may help to prevent this disease. " The study was funded by grants from the National Institute of Environmental Health Sciences, the US Environmental Protection Agency, the South Coast Air Quality Management District, and the Hastings Foundation.
Which one is NOT the reason that children increase risk of developing asthma?
选项 A、There exists traffic-related pollution.
B、Schools are located in heavy-traffic areas.
C、Children are frequently exposed to pollution.
D、The vehicles increase rapidly.
答案D
解析 [D]不是一个必然的原因，车辆不断增加，但可以让孩子少接触交通密集的地方，或减少交通相关的污染都可以降低哮喘病的发病风险。第二段中提到Asthma…has been linked to environmental factors such as traffic-related air pollution，所以交通污染也是原因，即[A]。文章首段提到了患哮喘病的风险不断增加，原因是孩子们的学校位于交通密集的地区，这是原因之一，也就是[B]。第二段末句提到经常暴露于污染的环境中也会影响哮喘病的发病风险，[C]也是原因。故不是增加孩子们患哮喘病风险的原因只有[D]，所以[D]为正确答案。  
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