• Deadly smog events in the 20th century led to important insights and research into
the toxicity of outdoor air pollutants.
• Early studies of air pollution, such as the Harvard Six Cities Study, used data from a
single air monitoring station to assign a pollution exposure value for all people
living in a city, whereas newer studies used data from more diverse sources
to assign specific exposure values for people living in different parts of a city.
• New ways to estimate air pollution, such as land use regression, have enhanced
estimates of ambient air pollution concentrations to within a few city blocks.
• Traffic-related air pollutants vary in kind and quantity over time and from one
neighbourhood to another, but usually include nitrogen dioxide (NO2), sulfur dioxide
(SO2), and particulate matter (PM).
• Particulate matter less than 2.5 microns in diameter (PM2.5) is small enough to
reach the lungs and is strongly associated with adverse health effects.
• Exposure to all traffic-related pollutants is most commonly, although not exclusively,
associated with respiratory disease and cardiovascular disease.
• Paying more attention to socioeconomic status has led to advancements in our
understanding of the impact of air pollution on health.