Short-term mechanisms of toxic action of airborne particulates underlie dose-rate dependent health risks and support control of one-hour airborne particle levels
Twenty-four-hour airborne particle mass levels permissible under the NAAQS have been associated with mortality and morbidity in communities, motivating reconsideration of the standard. Reports of shorter-term mechanisms of toxic action exerted by airborne PM and PM constituents are emerging. The mechanisms are diverse, but have in common a short time frame of toxic action, from minutes to hours. In view of documented PM excursions also lasting minutes to hours, this study inquires whether such short-term mechanisms might contribute to explaining daily morbidity and mortality. Toxicology experiments have demonstrated the harmfulness of brief exposure to PM levels in the range of observed excursions. This suggests that toxicological processes initiated by short-term inhalation of PM may exert clinically important effects, and that weak associations of 24-hour-average particle mass with mortality and morbidity may represent artifacts of stronger, shorter-term associations whose full magnitude remains to be quantified. In one study, the area of lung surface developing lesions was elevated in rats breathing the same four-hour dose of aerosols, when the four-hour average rate of aerosol delivery included a short-term (five-minute) burst fifty percent above the average dose rate. Elevations were observed with each of two aerosols tested. The magnitude of the effect was higher with one of the two aerosols, whose dose rate included four excursions rather than just one excursion. Particulate matter inhaled or instilled intratracheally has produced morbidity in animals, including apnea and electrophysiological effects in dogs. Other studies reveal that PM can kill rats via electrophysiological and possibly other mechanisms. PM has also adversely affected asthmatic people in controlled clinical settings during exercise or, in one study, at rest.
- Research Organization:
- RAM TRAC Corp., Schenectady, NY (US)
- OSTI ID:
- 20002251
- Report Number(s):
- CONF-990608-; TRN: IM200002%%251
- Resource Relation:
- Conference: Air and Waste 92nd Annual Meeting and Exhibition, St. Louis, MO (US), 06/20/1999--06/24/1999; Other Information: 1 CD-ROM. Operating Systems: Windows 3.1, '95, '98 and NT; Macintosh; and UNIX; PBD: 1999; Related Information: In: Air and Waste 92nd annual meeting and exhibition proceedings, [9500] pages.
- Country of Publication:
- United States
- Language:
- English
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