Secondhand tobacco smoke exposure in open and semi-open settings: a systematic review

Environ Health Perspect. 2013 Jul;121(7):766-73. doi: 10.1289/ehp.1205806. Epub 2013 May 7.


Background: Some countries have recently extended smoke-free policies to particular outdoor settings; however, there is controversy regarding whether this is scientifically and ethically justifiable.

Objectives: The objective of the present study was to review research on secondhand smoke (SHS) exposure in outdoor settings.

Data sources: We conducted different searches in PubMed for the period prior to September 2012. We checked the references of the identified papers, and conducted a similar search in Google Scholar.

Study selection: Our search terms included combinations of "secondhand smoke," "environmental tobacco smoke," "passive smoking" OR "tobacco smoke pollution" AND "outdoors" AND "PM" (particulate matter), "PM(2.5)" (PM with diameter ≤ 2.5 µm), "respirable suspended particles," "particulate matter," "nicotine," "CO" (carbon monoxide), "cotinine," "marker," "biomarker" OR "airborne marker." In total, 18 articles and reports met the inclusion criteria.

Results: Almost all studies used PM(2.5) concentration as an SHS marker. Mean PM(2.5) concentrations reported for outdoor smoking areas when smokers were present ranged from 8.32 to 124 µg/m(3) at hospitality venues, and 4.60 to 17.80 µg/m(3) at other locations. Mean PM(2.5) concentrations in smoke-free indoor settings near outdoor smoking areas ranged from 4 to 120.51 µg/m(3). SHS levels increased when smokers were present, and outdoor and indoor SHS levels were related. Most studies reported a positive association between SHS measures and smoker density, enclosure of outdoor locations, wind conditions, and proximity to smokers.

Conclusions: The available evidence indicates high SHS levels at some outdoor smoking areas and at adjacent smoke-free indoor areas. Further research and standardization of methodology is needed to determine whether smoke-free legislation should be extended to outdoor settings.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review
  • Systematic Review

MeSH terms

  • Air Pollutants / analysis*
  • Air Pollutants / metabolism
  • Air Pollution, Indoor / analysis
  • Biomarkers / metabolism
  • Environmental Exposure*
  • Environmental Monitoring
  • Particulate Matter / analysis*
  • Smoking Prevention
  • Tobacco Smoke Pollution / analysis*
  • Tobacco Smoke Pollution / prevention & control


  • Air Pollutants
  • Biomarkers
  • Particulate Matter
  • Tobacco Smoke Pollution