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Studying the effectiveness of activated carbon R95 respirators in reducing the inhalation of combustion by-products in Hanoi, Vietnam: a demonstration study

Heiman FL Wertheim12*, Dang Minh Ngoc3, Marcel Wolbers12, Ta Thi Binh3, Nguyễn Thị Thanh Hải3, Nguyễn Quỳnh Loan3, Phạm Thanh Tú3, Andreas Sjodin4, Lovisa Romanoff4, Zheng Li4, Jochen F Mueller5, Karen Kennedy5, Jeremy Farrar12, Kasia Stepniewska6, Peter Horby12, Annette Fox12 and Nguyen Duy Bao3

Author Affiliations

1 Oxford University Clinical Research Unit and Wellcome Trust Major Overseas Programme, Hanoi, Vietnam

2 Nuffield Department of Clinical Medicine, Oxford, United Kingdom

3 National Institute of Occupational and Environmental Health, Hanoi, Vietnam

4 Centers for Disease Control and Prevention, Atlanta, USA

5 The University of Queensland, The National Research Center for Toxicology (Entox), Queensland, Australia

6 Mahidol-Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand

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Environmental Health 2012, 11:72  doi:10.1186/1476-069X-11-72

Published: 26 September 2012



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.


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).


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).


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.

Trial registration

ISRCTN74390617 (date of assignation: 04/08/2009).

Urine; Pollution; Urban; Polycyclic aromatic hydrocarbons; PAH; 1-hydroxypyrene; Respirator