Saturday, January 10, 2009

A No Effect Level for Particulate Air Pollution Exposure Well Below Established Air Quality Standards

Inhalation Toxicology, Volume 21, Issue 1 January 2009 , pages 38 - 47
Effects of Ambient Air Particulate Exposure on Blood-Gas Barrier Permeability and Lung Function
Authors: Elvira Vaclavik Bruner a; Jann Mortensen b; Peter Mller a; Alfred Bernard c; Peter Vinzents a; Peter Whlin d; Marianne Glasius d; Steffen Loft a
Affiliations:
a Institute of Public Health, Department of Environmental Health, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
b Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Faculty of Health Sciences, University hospital of Copenhagen, Copenhagen, Denmark
c School of Public Health. Faculty of Medicine, Catholic University of Louvain, Louvain, Belgium
d Department of Atmospheric Environment, National Environmental Research Institute, Roskilde, Denmark

Abstract
Particulate air pollution is associated with increased risk of pulmonary diseases and detrimental outcomes related to the cardiovascular system, including altered vessel functions. This study's objective was too evaluate the effects of ambient particle exposure on the blood-gas permeability, lung function and Clara cell 16 (CC16) protein release in healthy young subjects. Twenty-nine nonsmokers participated in a randomized, two-factor crossover study with or without biking exercise for 180 min and with 24-h exposure to particle-rich (6169-15,362 particles/cm3; 7.0-11.6 μg/m3 PM2.5; 7.5-15.8 μg/m3 PM10-2.5) or filtered (91-542 particles/cm3) air collected above a busy street. The clearance rate of aerosolized 99mTc-labeled diethylenetriamine pentaacetic acid (99mTc-DTPA) was measured as an index for the alveolar epithelial membrane integrity and permeability of the lung blood-gas barrier after rush-hour exposure. Lung function was assessed using body plethysmography, flow-volume curves, and measurements of the diffusion capacity of carbon monoxide. CC16 was measured in plasma and urine as another marker of alveolar integrity. Particulate matter exposure had no significant effect on the epithelial membrane integrity using the methods available in this study. Exercise increased the clearance rate of 99mTc-DTPA indicated by a 6.8% (95% CI: 0.4-12.8%) shorter half-life and this was more pronounced in men than women. Neither particulate matter exposure nor exercise had an effect on the concentration of CC16 in plasma and urine or on the static and dynamic volumes or ventilation distribution of the lungs. The study thus demonstrates increased permeability of the alveolar blood-gas barrier following moderate exercise, whereas exposure to ambient levels of urban air particles has no detectable effects on the alveolar blood-gas barrier or lung function.
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BrooklynDodger(s) comment: What do the Dodger(s) intend by posting a null study? Sometimes a No Observed Adverse Effect Level is useful in risk assessment. The Dodger(s) remind(s) the reader that a robust NOAEL below a LOAEL corresponds to a 10% attack rate. Null studies are attached to an exposure level and regimen.
Clara cells are all the rage these days. The Clara cell resident in the lung has phagocytic, secretory and P450 type activity. The Dodger(s) think of Clara cells as being like Kuppfer cells in the liver - a population not thought of 30 years ago which is now likely involved in chemical injury. Differences in Clara cell activity figure in the Houdini Risk Assessment of solvent vapors which are consistently carcinogenic in the mouse lung but not the rat.
The NOAEL for increased release of clara cell secretory in healthy, non smoking human volunteers is an exposure for 24 hours to ambient type particulate less than 12 ug/m^3 for PM2.5 and maybe 27 ug/m^3 for PM10. The current EPA NAAQS for 24-hour exposures are 35 ug/m^3 and 150 ug/m^3. This appears to have been some pretty clean days in Copenhagen. The Dodger(s) couldn't get the full text because full text Inhalation Toxicology is hard to find. So the Dodger(s) don't know the effect level for increased release of this protein, if it is known.

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