title: Airborne particulate matter (PM2.5) and the prevalence of allergic conjunctivitis in Japan.
abstract: OBJECTIVE
  Exposure to particulate matter less than 2.5 μm in diameter (PM2.5) is associated with asthma and respiratory symptoms, but little is known about the influence of PM2.5 on allergic conjunctivitis. The purpose of this study was to examine the association of PM2.5 with outpatient attendance for allergic conjunctivitis.
  
  
  METHODS
  We conducted a time-series analysis of the association between outpatient attendance for allergic conjunctivitis and PM2.5 levels from May to July (non-pollen season) and from August to October (the autumnal pollen season) in 2012. Air pollution data (including the levels of PM2.5, oxidants, nitric oxide, nitrogen dioxide, nitrogen oxide, carbon monoxide, methane, non-methane hydrocarbons, and total hydrocarbons) and data on the daily weather conditions (temperature, wind speed, and humidity) were collected at a centrally located monitoring station in Tokyo. We calculated weekly average values for the daily number of outpatient visits, as well as the air pollution and weather data, and used the weekly average values for analysis.
  
  
  RESULTS
  There was a significant association between the number of outpatient visits for allergic conjunctivitis and the PM2.5 level (r=0.62, p=0.0177) from May to July, while no correlation was found between the number of outpatient visits and any variable assessed from August to November. Multivariate analysis also showed that PM2.5 was a significant predictor of the number of outpatient visits from May to July (odds ratio=9.05, p=0.0463), while there were no significant predictors of the number of outpatient visits from August to October. From May to July, PM2.5 showed a negative correlation with humidity (r=-0.53, p=0.0499).
  
  
  CONCLUSIONS
  These findings suggest a possible role of PM2.5 in the development of allergic conjunctivitis during the non-pollen season. This association between PM2.5 and allergic conjunctivitis may have broad public health implications in relation to allergic diseases.
authors.affiliation: Department of Ophthalmology, Tokyo Women's Medical University Medical Center East, Tokyo, Japan; Department of Ophthalmology, University of Tokyo Graduate School of Medicine, Tokyo, Japan; Nerima West Eye Clinic, Tokyo, Japan. Electronic address: mimurat-tky@umin.ac.jp.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Mimura
authors.affiliation: Department of Health Science, Oita University of Nursing and Health Science, Oita, Japan.
authors.forename: Takamichi
authors.initials: T
authors.lastname: Ichinose
authors.affiliation: Department of Ophthalmology, Tokyo Women's Medical University Medical Center East, Tokyo, Japan; Department of Ophthalmology, University of Tokyo Graduate School of Medicine, Tokyo, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Yamagami
authors.affiliation: Department of Ophthalmology, Tsurumi University School of Dental Medicine, Kanagawa, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujishima
authors.affiliation: Department of Ophthalmology, Tokyo Women's Medical University Medical Center East, Tokyo, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kamei
authors.affiliation: Department of Ophthalmology, Tokyo Women's Medical University Medical Center East, Tokyo, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Goto
authors.affiliation: Department of Ophthalmology, Tokyo Women's Medical University Medical Center East, Tokyo, Japan; Department of Ophthalmology, University of Tokyo Graduate School of Medicine, Tokyo, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Takada
authors.affiliation: Department of Ophthalmology, Tokyo Women's Medical University Medical Center East, Tokyo, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Matsubara
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data; D003233:Conjunctivitis, Allergic / Q000453:epidemiology*; D004784:Environmental Monitoring; D006801:Humans; D019570:Inhalation Exposure / Q000706:statistics & numerical data*; D007564:Japan / Q000453:epidemiology; D052638:Particulate Matter / Q000032:analysis*; D015995:Prevalence; D014887:Weather
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
keywords: Air pollution; Allergic conjunctivitis; Outpatient attendance; PM2.5