Abstract for presentation at 14th IUAPPA World Congress

There has been increasing interest over recent years into the effect of ultrafine particles (UFP) on human cardiovascular and respiratory health. The adverse health impacts resultant of particle exposure are currently attributed to the mass concentration or the chemical composition of particles smaller than 10 mm (PM10) or 2.5 mm (PM2.5) in diameter. However, it has been hypothesised that it is UFP (< 0.1 mm) measured in terms of number concentration that might be the most responsible for the observed health effects. This presentation will discuss the results of a study aimed at analysing the state of health science in terms of epidemiological evidence for the health impacts of UFP. In summary, the array of epidemiological studies conducted so far, suggests that UFP exposure is associated with human mortality and respiratory and cardiovascular morbidity, despite considerable gaps of knowledge and some inconsistencies that were found between the studies, based on certain deficiencies in the studies design. This limited number of epidemiological studies indicates that there are comparable health effects between fine and ultrafine particles, despite appearing to be independent of each other. The main distinguishing feature between the two is that fine particles tend to show more immediate effects, whilst ultrafine particles show delayed effects on mortality. However, at present, the database is too geographically restricted and too limited (in terms of both the number of studies and the number of subjects), to allow clear conclusions on the mode of action or generalisation to other settings. Consequently, it is recommended that further better designed studies be initiated to improve our understanding of the health impacts of UFP.