Département santé-environnement, programme de surveillance air et santé, Institut de veille sanitaire, 12, rue du Val-d’Osne, 94415 Saint-Maurice cedex, France
Particles are considered to be ultrafine (UFP) when their diameter is less than 0.1 μm. After emission into the ambient air during combustion processes or secondary formation by reactions between other ambient air pollutants, they can be inhaled and then deposited in the respiratory tract where, experimental studies show, they can induce harmful effects. Several epidemiological studies have sought to analyse the short-term relations between UFP exposure and health. A review of these studies allows us to identify the methodological issues that they encounter, due mainly to the scarcity of UFP measurements in the ambient air and to the problems related to using these measurements for exposure assessment. It also shows that the results of these studies, despite their differences, tend to indicate that inhalation of UFP has some short-term effects on respiratory and cardiovascular health. The development of nanotechnologies, which intentionally produce such particles, underlines the need for more epidemiological studies on a broader range of health effects after both short-term and chronic exposure.