Thermal release of nitric oxide from ambient air and diesel particles

In recent years there have been numerous reports of an association between daily increases in particle air pollution (PM10) and daily increases in mor tality and morbidity. Despite these reports, there continue to be unresolve d issues with these studies, including the issue of a plausible biological mechanism by which small increases in daily particle levels could cause adv erse human health effects. Chemical characterization of particles is a crit ical step in testing any biological mechanism. We have characterized gas-ph ase material associated with particles from various sources and found that measurable amounts of nitric oxide (NO) can be thermally released from thes e particles. NO is well-known to be an effective vasodilating agent at very low concentrations. In this work, release of NO from four NIST reference m aterials, two ambient air particulate samples, and two diesel particulate s amples was quantified after heating the samples for 1 h. The amount of NO o riginating from particles depends on the temperature used to evolve this ga s. NO levels ranged from 0.005 ng of NO/mg of sample at 37 degrees C to 190 0 ng of NO/mg of sample at 140 degrees C. These experiments demonstrate tha t nitric oxide can be released from some particles at physiological tempera tures (37 degrees C).