title: pH increase observed in exhaled breath condensate from welding fume exposure.
abstract: OBJECTIVE
  We sought to investigate changes in exhaled breath condensate (EBC) pH in healthy workers exposed to welding fumes.
  
  
  METHODS
  Fourteen exposed participants (median age 39 years, 5 smokers) and 8 nonexposed controls (median age 44 years, 1 smoker) were monitored at an apprentice welding school. Exposure to fine particulate matter less than 2.5 microm (PM2.5) was assessed using cyclone samplers. EBC samples were collected at baseline and at the end of the work shift. EBC samples were deaerated using argon and pH values were measured using standard pH microelectrodes.
  
  
  RESULTS
  Mean +/- SEM PM2.5 levels were 1.17 +/- 0.18 mg/m for exposed subjects and 0.03 +/- 0.01 mg/m for controls. Baseline median (range) EBC pH values for the control and exposed group were similar (P = 0.86), 7.21 (4.91 to 8.26), and 7.39 (4.85 to 7.79), respectively. The exposed subjects had a small-but-marginally significant (P = 0.07) pre- to post-work shift increase in pH of 0.28, whereas the control group showed a minimal increase of only 0.03 (P = 0.56). Compared with the control group, the exposed group had a median cross-shift pH increase of 0.25 (P = 0.49).
  
  
  CONCLUSIONS
  The aerosolized fine particulate matter contained in metal fumes may be associated with an acute increase in EBC pH values. Further study is necessary to investigate the acute rise in EBC pH after acute exposure to welding fume.
authors.affiliation: Department of Environmental Health, Occupational Health Program, Harvard School of Public Health, Boston, Massachusetts 02115, USA. paulboyce@post.harvard.edu
authors.forename: Paul D
authors.initials: PD
authors.lastname: Boyce
authors.forename: Jee Young
authors.initials: JY
authors.lastname: Kim
authors.forename: David N
authors.initials: DN
authors.lastname: Weissman
authors.forename: John
authors.initials: J
authors.lastname: Hunt
authors.forename: David C
authors.initials: DC
authors.lastname: Christiani
mesh_terms: D000328:Adult; D001944:Breath Tests; D004784:Environmental Monitoring / Q000379:methods*; D005740:Gases; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019570:Inhalation Exposure / Q000032:analysis*; D008875:Middle Aged; D016273:Occupational Exposure / Q000032:analysis*; D011014:Pneumonia / Q000139:chemically induced* / Q000378:metabolism*; D014896:Welding
chemical_list: D005740:Gases