To date, most epidemiological studies of paediatric pulmonary disease and air pollution have focused on the impacts of air pollutants that are both regulated and monitored on a daily basis by governments. This includes particle mass concentrations and gaseous air pollutants such as ozone and sulfur dioxide. In most studies this has led to the use of available regional air monitoring data. Generally, these approaches have resulted in important new information about ongoing health impacts in many nations or have confirmed previous findings of adverse associations with respiratory morbidity. This has justified calls for greater involvement by citizens, local community organisations, industry, and governments to curb air pollutant exposures.¹ However, there is increasing evidence that concentrations of air pollutants—especially particle components and size distributions not routinely monitored—have spatial distributions that can vary by neighbourhood. In urban areas the most prevalent determinant of sub-regional air pollutant concentrations is local traffic. Roadway traffic will continue to increase worldwide, as evidenced by projections that transportation energy consumption in emerging economies such as China will increase at an annual rate from 2002 to 2015 of 4.4 quadrillion Btu (1055.1 Joule/Btu).²

WHAT IS IMPORTANT ABOUT PROXIMITY TO TRAFFIC?

Concentrations of ultrafine particles <100 nm in diameter are influenced strongly and positively by distance from roadways.³ There is also growing evidence that photochemically generated ultrafine particles are a potentially important regional exposure.³ Ultrafine particles have low mass concentrations in air compared with regulated particulate matter <10 μm in diameter (PM₁₀). However, the large surface area per unit mass of ultrafine particles can carry to the lungs large quantities of toxic air pollutants including oxidant gases, organic compounds, and transition metals.⁴ This toxicity of ultrafine particles is combined with their high pulmonary deposition …