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Incident rates of chronic rhinosinusitis (CRS) in Fire Department of the City of New York (FDNY) cohort by exposure group throughout study period (11 September 2001 to 10 September 2011). High exposure: arrived morning of 11 September 2001. Moderate exposure: arrived afternoon of 11 September 2001 or anytime 12 September 2001. Low exposure: arrived any day between 13 September 2001 and 24 September 2001.
