Environmental tobacco smoke exposure among non-smoking waiters: measurement of expired carbon monoxide levels

Sao Paulo Med J. 2000 Jul 6;118(4):89-92. doi: 10.1590/s1516-31802000000400003.


Context: Exposure to environmental tobacco smoke is a health risk that is of concern to patrons and of particular concern to employees of restaurants and bars.

Objective: To assess environmental tobacco smoke exposure (using expired carbon monoxide levels) in non-smoking waiters before and after a normal day's shift and to compare pre-exposure levels with non-smoking medical students.

Design: An observational study.

Setting: Restaurants with more than 50 tables or 100 places in São Paulo.

Subjects: 100 non-smoking restaurant waiters and 100 non-smoking medical students in São Paulo, Brazil.

Main measurements: Levels of expired carbon monoxide, measured with a Smokerlyser (Bedfont EC 50 Scientific), before and after a normal day's work.

Results: Waiters' pre-exposure expired carbon monoxide levels were similar to those of medical students, but after a mean of 9 hours exposure in the workplace, median levels more than doubled (2.0 ppm vs. 5.0 ppm, P <0.001). Post-exposure carbon monoxide levels were correlated with the number of tables available for smokers (Kendall's tau = 0.2, P <0.0001).

Conclusions: Exposure to environmental tobacco smoke is the most likely explanation for the increase in carbon monoxide levels among these non-smoking waiters. These findings can be used to inform the ongoing public health debate on passive smoking.

MeSH terms

  • Adolescent
  • Adult
  • Breath Tests
  • Carbon Monoxide / analysis*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Occupational Exposure / analysis*
  • Restaurants*
  • Statistics, Nonparametric
  • Students, Medical
  • Tobacco Smoke Pollution / analysis*
  • Workplace


  • Tobacco Smoke Pollution
  • Carbon Monoxide