Effects of Ultrafine Particles in the Lung and Potential Relevance to Environmental Particles

A number of epidemiological studies has been published over the past 5 years which reported an association between low ambient particle concentration (< 100 μg/m3) and acute morbidity and even mortality in the elderly. Since larger particles above ~ 0.3 μm cannot explain such dramatic effects we hypothesize that ultrafine particles (< 50 nm) present in the urban atmosphere at high number concentrations may be causally involved. We have evaluated this hypothesis by using model ultrafine particles of Teflon® fume with diameters of 10–26 nm. These particles when inhaled by rats proved to be extremely toxic, leading to severe hemorrhagic pulmonary edema and even death at short-exposure durations (10–30 minutes) and particle number concentration of l–5×l05 particles/cm3. The respective calculated mass concentrations are in the range of 30–60 μg/m3. We conclude that certain ultrafine particles when inhaled as singlet particles can be highly toxic and that there is a need to study more closely environmentally occurring ultrafine particles.