Dynamic increases in the number of vehicles, particularly in large urban areas, cause a visible decline in the average speed of cars. Street networks are not able to efficiently handle generated traffic, which could result in increasing levels of air pollutant emissions and consequently in a greater incidence of people suffering from respiratory diseases. This study presents the effects of investigations on the influence of traffic-related air pollutants on inhabitants of two Polish cities living in the proximity of busy roads. As a control group rural area residents were taken. In 2005-2006 and 2008-2009 respiratory function tests were conducted on a group of 3,506 people (including residents of non-urban areas). The investigation has shown that people living near busy urban roads had a significant increase in the risk of bronchi obstruction.