Kunzli's research builds upon two decades of studies which show that air pollution contributes to death and illness, with some effects related to short term exposure and some effects to long term exposure. Recent research guiding air quality standards in the United States suggests fine airborne particulate matter could lead to cardiac problems, not just respiratory effects, in some segments of the population. The smallest of the fine particulates penetrate deep into the tissues of the lung, where they can cause a variety of health problems. Kunzli's study found that pollution from motorized traffic also accounted for more than 25,000 new cases of chronic bronchitis, more than 500,000 asthma attacks, and more than 16 million person days of restricted activities.
Traffic related air pollution remains a key target for public health action in Europe.
Kunzli's team quantified the effects of air pollution by measuring specific increases in the concentration of inhalable particles less than 10 micrometers, or 10 millionths of a meter, across, designated as PM10 particles. Cases of illness and death in different areas were matched against PM10 levels. The results showed that although the risk to the individual remained small, the effect on the population as a whole was significant. The study found that the cost of treating illness associated with traffic pollution across the three countries amounted to 1.7 percent of their gross domestic products, more than the costs arising from traffic accidents. Such costs cause economic problems, because they are not included in the market price, which leads to a wasting of scarce and important resources, eg, clean air, silence, and clean water.