The ULTRA project was conducted by a consortium of researchers and public health professionals in Finland, the Netherlands, Germany, and Belgium who sought an answer to the question of exactly what type of air pollution causes health problems, and what are the characteristics of these airborne particles. Air pollution, also called ambient air particulate pollution, is measured as PM10 or PM2.5 and is widely held responsible for cardiopulmonary problems. Such health problems include declines in lung function, as well as cardiopulmonary symptoms, and can lead to serious health implications such as hospital admissions and even mortality. The objective of the ULTRA project is to expand the scope of knowledge that has been obtained thus far of how people in Europe respond upon exposure to particulate matter of diverse size and chemical composition, and to determine the subsequent health risks. In order to compile and integrate all this information, a specific methodology was constructed as part of the ULTRA project. Firstly, three aerosol spectrometers in three different European cities measured continuous concentrations and size distributions of air particles in the ambient city atmosphere. These particle counters were the German Mobile Aerosol Spectrometer (MAS), and the Electric Aerosol Spectrometer (EAS). The MAS comprised two different sensors that monitored different size ranges. The EAS used the electrical measurement principal as a quantitative basis. These measurements were subsequently compared to each other and to other particle measurement techniques. The second phase of the project consisted of both human health supervision and particle number and size monitoring. Health monitoring was achieved via three panel studies in three cities. One hundred and thirty one people between the ages of 40 and 84 were observed in Amsterdam, the Netherlands, Erfurt, Germany, and Helsinki, Finland in order to determine the state of their cardiopulmonary health. These people had to undergo biweekly examinations over a period of six months, where blood pressure, and biomarkers for lung damage from urine samples were measured. Also, cardiopulmonary functions were recorded via spirometry, and ECGs. Simultaneously, air particle number concentrations and size distributions, as well as levels of gaseous pollutants in the ambient air were quantified. Levels of PM2.5 were recorded on a 24-hour basis. This intense multifaceted monitoring was conducted so as to link daily fluctuations in air pollution to respiratory and heart symptoms. In fact, symptoms could be traced back to specific dates and times because the subjects kept daily symptom diaries. Ultimately, ultrafine particles and PM2.5 were linked to symptoms and heart rate variability. Also, a biomarker of lung damage (CC16) was also connected to high levels of PM2.5. On the other hand, other symptoms (such as blood pressure and heart rate) experienced by subjects in the three panel studies were not constantly linked to air pollution. In essence, the results of the ULTRA project could assist in the improvement of air quality standards in Europe, and in alleviating air pollution-related health problems.