Potential Health Effects of Respirable Particles
Worldwide, air pollution kills approximately 500,000 people each year. Based on epidemiological studies, most of these deaths are caused by the inhalation of fine particles (i.e., those with diameters below approximately 2.5 micrometers). Despite this, the types of particles that are toxic, and the reasons for this toxicity, are still largely unknown.

In our lab we have two projects related to particle toxicity. The first involves quantifying the amounts of •OH generated when PM deposits in the lung (using a simulated lung fluid as a surrogate). Because of its high reactivity, •OH can damage DNA and other cellular components and is thought to be an important contributor to oxidative stress. We have found that soot particles form •OH, but that ambient particles are more efficient at generating •OH, primarily because of chemistry involving transition metals. Because of the importance of metals in generating •OH, we are examining the efficiency of •OH formation from dissolved and particulate metals as well as ambient particles in a simulated lung fluids. The second project that we are working on related to particle toxicity involves examining how atmospheric reactions alter the oxidation states (and, therefore, the toxicity) of particulate metals. Much of this work has focused on chromium (Cr), which is interesting because it has two major oxidation states: III, which is a trace nutrient, and VI, which is toxic and carcinogenic. Our results show that that atmospheric aging converts particle-bound Cr(VI) to Cr(III) with a timescale of approximately a week, which is good news for those of us who breathe.