title: A systematic review of the physical health impacts from non-occupational exposure to wildfire smoke.
abstract: BACKGROUND
  Climate change is likely to increase the threat of wildfires, and little is known about how wildfires affect health in exposed communities. A better understanding of the impacts of the resulting air pollution has important public health implications for the present day and the future.
  
  
  METHODS
  We performed a systematic search to identify peer-reviewed scientific studies published since 1986 regarding impacts of wildfire smoke on health in exposed communities. We reviewed and synthesized the state of science of this issue including methods to estimate exposure, and identified limitations in current research.
  
  
  RESULTS
  We identified 61 epidemiological studies linking wildfire and human health in communities. The U.S. and Australia were the most frequently studied countries (18 studies on the U.S., 15 on Australia). Geographic scales ranged from a single small city (population about 55,000) to the entire globe. Most studies focused on areas close to fire events. Exposure was most commonly assessed with stationary air pollutant monitors (35 of 61 studies). Other methods included using satellite remote sensing and measurements from air samples collected during fires. Most studies compared risk of health outcomes between 1) periods with no fire events and periods during or after fire events, or 2) regions affected by wildfire smoke and unaffected regions. Daily pollution levels during or after wildfire in most studies exceeded U.S. EPA regulations. Levels of PM10, the most frequently studied pollutant, were 1.2 to 10 times higher due to wildfire smoke compared to non-fire periods and/or locations. Respiratory disease was the most frequently studied health condition, and had the most consistent results. Over 90% of these 45 studies reported that wildfire smoke was significantly associated with risk of respiratory morbidity.
  
  
  CONCLUSIONS
  Exposure measurement is a key challenge in current literature on wildfire and human health. A limitation is the difficulty of estimating pollution specific to wildfires. New methods are needed to separate air pollution levels of wildfires from those from ambient sources, such as transportation. The majority of studies found that wildfire smoke was associated with increased risk of respiratory and cardiovascular diseases. Children, the elderly and those with underlying chronic diseases appear to be susceptible. More studies on mortality and cardiovascular morbidity are needed. Further exploration with new methods could help ascertain the public health impacts of wildfires under climate change and guide mitigation policies.
authors.affiliation: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511, USA. Electronic address: coco.liu@yale.edu.
authors.forename: Jia C
authors.initials: JC
authors.lastname: Liu
authors.affiliation: Center for Perinatal Pediatric and Environmental Epidemiology, School of Medicine, Yale University, New Haven, CT 06511, USA. Electronic address: gavin.pereira@yale.edu.
authors.forename: Gavin
authors.initials: G
authors.lastname: Pereira
authors.affiliation: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511, USA. Electronic address: sarah.uhl@gmail.com.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Uhl
authors.affiliation: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511, USA. Electronic address: mbravo@med.umich.edu.
authors.forename: Mercedes A
authors.initials: MA
authors.lastname: Bravo
authors.affiliation: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511, USA. Electronic address: michelle.bell@yale.edu.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Bell
mesh_terms: D001315:Australia; D004781:Environmental Exposure; D005390:Fires; D006801:Humans; D012906:Smoke / Q000009:adverse effects*; D014481:United States
chemical_list: D012906:Smoke
keywords: Air pollution; Forest Fire; Health; Smoke; Wildfire