In recent years there have been numerous reports of an association between daily increases in particle air pollution (PM10) and daily increases in mortality and morbidity. Despite these reports, there continue to be unresolved issues with thesestudies, including the issue of a plausible biological mechanism by which small increases in daily particle levels could cause adverse human health effects. Chemical characterization of particles is a critical step in testing any biological mechanism. Wehave characterized gas-phase material associated with particles from various sources and found that measurable amounts of nitric oxide (NO) can be thermally released from these particles. NO is well-known to be an effective vasodilating agent at very lowconcentrations. In this work, release of NO from four NIST reference materials, two ambient air particulate samples, and two diesel particulate samples was quantified after heating the samples for 1 h. The amount of NO originating from particles dependson the temperature used to evolve this gas. NO levels ranged from 0.005 ng of NO/mg of sample at 37℃ to 1900 ng of NO/mg of sample at 140℃. These experiments demonstrate that nitric oxide can be released from some particles at physiological temperatures (37℃).
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