title: Studying the effectiveness of activated carbon R95 respirators in reducing the inhalation of combustion by-products in Hanoi, Vietnam: a demonstration study.
abstract: BACKGROUND
  Urban air pollution is an increasing health problem, particularly in Asia, where the combustion of fossil fuels has increased rapidly as a result of industrialization and socio-economic development. The adverse health impacts of urban air pollution are well established, but less is known about effective intervention strategies. In this demonstration study we set out to establish methods to assess whether wearing an R95 activated carbon respirator could reduce intake of polycyclic aromatic hydrocarbons (PAH) in street workers in Hanoi, Vietnam.
  
  
  METHODS
  In this demonstration study we performed a cross-over study in which non-smoking participants that worked at least 4 hours per day on the street in Hanoi were randomly allocated to specific respirator wearing sequences for a duration of 2 weeks. Urines were collected after each period, i.e., twice per week, at the end of the working day to measure hydroxy PAHs (OH-PAH) using gas chromatography/high resolution mass spectrometry. The primary endpoint was the urinary concentration of 1-hydroxypyrene (1-OHP).
  
  
  RESULTS
  Forty-four participants (54.5% male, median age 40 years) were enrolled with the majority being motorbike taxi drivers (38.6%) or street vendors (34.1%). The baseline creatinine corrected urinary level for 1-OHP was much higher than other international comparisons: 1020 ng/g creatinine (IQR: 604-1551). Wearing a R95 mask had no significant effect on 1-OHP levels: estimated multiplicative effect 1.0 (95% CI: 0.92-1.09) or other OH-PAHs, except 1-hydroxynaphthalene (1-OHN): 0.86 (95% CI: 0.11-0.96).
  
  
  CONCLUSIONS
  High levels of urine OH-PAHs were found in Hanoi street workers. No effect was seen on urine OH-PAH levels by wearing R95 particulate respirators in an area of high urban air pollution, except for 1-OHN. A lack of effect may be de to gaseous phase PAHs that were not filtered efficiently by the respirator. The high levels of urinary OH-PAHs found, urges for effective interventions.
  
  
  BACKGROUND
  ISRCTN74390617 (date of assignation: 04/08/2009).
authors.affiliation: Oxford University Clinical Research Unit and Wellcome Trust Major Overseas Programme, Hanoi, Vietnam. heiman.wertheim@gmail.com
authors.forename: Heiman F L
authors.initials: HF
authors.lastname: Wertheim
authors.forename: Dang Minh
authors.initials: DM
authors.lastname: Ngoc
authors.forename: Marcel
authors.initials: M
authors.lastname: Wolbers
authors.forename: Ta Thi
authors.initials: TT
authors.lastname: Binh
authors.forename: Nguyễn Thị Thanh
authors.initials: NT
authors.lastname: Hải
authors.forename: Nguyễn Quỳnh
authors.initials: NQ
authors.lastname: Loan
authors.forename: Phạm Thanh
authors.initials: PT
authors.lastname: Tú
authors.forename: Andreas
authors.initials: A
authors.lastname: Sjodin
authors.forename: Lovisa
authors.initials: L
authors.lastname: Romanoff
authors.forename: Zheng
authors.initials: Z
authors.lastname: Li
authors.forename: Jochen F
authors.initials: JF
authors.lastname: Mueller
authors.forename: Karen
authors.initials: K
authors.lastname: Kennedy
authors.forename: Jeremy
authors.initials: J
authors.lastname: Farrar
authors.forename: Kasia
authors.initials: K
authors.lastname: Stepniewska
authors.forename: Peter
authors.initials: P
authors.lastname: Horby
authors.forename: Annette
authors.initials: A
authors.lastname: Fox
authors.forename: Nguyen Duy
authors.initials: ND
authors.lastname: Bao
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000378:metabolism; D002244:Carbon / Q000737:chemistry; D004781:Environmental Exposure / Q000517:prevention & control*; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D019570:Inhalation Exposure / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D018986:Motor Vehicles; D009284:Naphthols / Q000652:urine; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism; D011721:Pyrenes / Q000652:urine; D012134:Respiratory Protective Devices; D014744:Vietnam
chemical_list: D000393:Air Pollutants; D009284:Naphthols; D011084:Polycyclic Aromatic Hydrocarbons; D011721:Pyrenes; D002244:Carbon; C033146:1-hydroxypyrene