Travelling to Polluted Cities: A Systematic Review on the Harm of Air Pollution on International Travellers' Health.

Rationale for Review: In 2019, approximately 1.4 billion people traveled internationally. Many individuals travel to megacities where air pollution concentrations can vary significantly. Short-term exposure to air pollutants, can cause morbidity and mortality related to cardiovascular and respiratory disease, with the literature clearly reporting a strong association between short-term exposure to particulate matter ≤ 2.5 micrometers and ozone with adverse health outcomes in resident populations. However, limited research has been conducted on the health impacts of short-term exposure to air pollution in individuals who travel internationally. The objective of this systematic review was to review the evidence for the respiratory and cardiovascular health impacts from exposure to air pollution during international travel to polluted cities, in adults aged ≥18 years old. Key Findings: We searched PubMed, Scopus, and EMBASE for studies related to air pollution and the health impacts on international travelers. Of the initially identified 115 articles that fit the search criteria, 6 articles were selected for the final review. All 6 studies found indications of adverse health impacts of air pollution exposure on international travelers, with most of the changes being reversible upon return to their home country/city. However, none of these studies contained large populations nor investigated vulnerable populations, such as children, elderly, or those with pre-existing conditions. Conclusions: More research is warranted to clearly understand the impacts of air pollution related changes on travelers' health, especially on vulnerable groups who may be at higher risk of adverse impacts during travel to polluted cities.