title: Correlation between signs and symptoms of ocular surface dysfunction and tear osmolarity with ambient levels of air pollution in a large metropolitan area.
abstract: OBJECTIVE
  To evaluate the effect of high levels of environmental air pollution on tear osmolarity and its possible correlation with clinical signs and symptoms.
  
  
  METHODS
  This was a panel study involving 71 taxi drivers and traffic controllers from São Paulo, Brazil. Mean individual levels of 24-hour exposure to nitrogen dioxide (NO2) and particulate matter smaller than 2.5 μm (PM2.5) were assessed on 4 different occasions. On the first and third visits, subjects were submitted to clinical evaluations including the administration of the Ocular Surface Disease Index questionnaire, slit-lamp examination, estimation of tear breakup time (BUT), the Schirmer test, and vital staining of the cornea and conjunctiva. On the second and fourth visits, tear samples were collected for osmolarity assays. Statistical analysis was performed using generalized estimating equations.
  
  
  RESULTS
  Although the taxi drivers and traffic controllers in our sample were exposed to high levels of NO2 and PM2.5, few symptoms were reported on the Ocular Surface Disease Index questionnaire. BUT values were reduced, whereas vital staining and Schirmer test mean results were within normal limits, despite considerable variability. A significant and negative correlation was found between PM2.5 levels and tear film osmolarity levels (P < 0.05). An increase of 10 μg/m(3) in PM2.5 was associated with a 10.9 mOsm/kg decrease in tear osmolarity. There also was a negative correlation, although not statistically significant, between NO2 and tear osmolarity.
  
  
  CONCLUSIONS
  Exposure to air pollution reduces tear film stability and influences tear film osmolarity. Combining clinical examination with the assessment of tear osmolarity may help understand ocular surface response to high levels of air pollution.
authors.affiliation: Department of Ophthalmology, Laboratory for Investigation in Ophthalmology (LIM-33), University of São Paulo Medical School, São Paulo, Brazil. andre_torri39@yahoo.com.br
authors.forename: André A M
authors.initials: AA
authors.lastname: Torricelli
authors.forename: Priscila
authors.initials: P
authors.lastname: Novaes
authors.forename: Monique
authors.initials: M
authors.lastname: Matsuda
authors.forename: Alfésio
authors.initials: A
authors.lastname: Braga
authors.forename: Paulo H N
authors.initials: PH
authors.lastname: Saldiva
authors.forename: Milton R
authors.initials: MR
authors.lastname: Alves
authors.forename: Mário L R
authors.initials: ML
authors.lastname: Monteiro
mesh_terms: D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000633:toxicity*; D001938:Brazil; D003229:Conjunctival Diseases / Q000209:etiology / Q000503:physiopathology*; D003316:Corneal Diseases / Q000209:etiology / Q000503:physiopathology*; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity; D009994:Osmolar Concentration; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity; D011446:Prospective Studies; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013666:Tears / Q000737:chemistry*; D014505:Urban Population
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D009585:Nitrogen Dioxide