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and the air on planes may be getting dirtier , with so many people flying these days a recent review of cabin air studies called for by the centers of disease control and prevention , found the research scientifically limited and recommended it be considered tentative .
 the centers of disease control and prevention, so many people, planes, cabin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: geographical social political, organization, person, location, facility, vehicle, weapon 
Text: {0} 
Answer:
 the centers of disease control and prevention, so many people, planes, cabin