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| Titel |
Generation of hydrogen peroxide from San Joaquin Valley particles in a cell-free solution |
| VerfasserIn |
H. Shen, A. I. Barakat, C. Anastasio |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 2 ; Nr. 11, no. 2 (2011-01-26), S.753-765 |
| Datensatznummer |
250009197
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| Publikation (Nr.) |
 copernicus.org/acp-11-753-2011.pdf |
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| Zusammenfassung |
| Epidemiological studies have shown a correlation between exposure to ambient
particulate matter (PM) and adverse health effects. One proposed mechanism
of PM-mediated health effects is the generation of reactive oxygen species
(ROS) – e.g., superoxide (•O2−), hydrogen peroxide (HOOH), and
hydroxyl radical (•OH) – followed by oxidative stress. There are very few
quantitative, specific measures of individual ROS generated from PM, but
this information would help to more quantitatively address the link between
ROS and the health effects of PM. To address this gap, we quantified the
generation of HOOH by PM collected at an urban (Fresno) and rural (Westside)
site in the San Joaquin Valley (SJV) of California during summer and winter
from 2006 to 2009. HOOH was quantified by HPLC after extracting the PM in a
cell-free, phosphate-buffered saline (PBS) solution with or without 50 μM
ascorbate (Asc). Our results show that the urban PM generally generates
much more HOOH than the rural PM but that there is no apparent seasonal
difference in HOOH generation. In nearly all of the samples the addition of
a physiologically relevant concentration of Asc greatly enhances HOOH
formation, but a few of the coarse PM samples were able to generate a
considerable amount of HOOH in the absence of added Asc, indicating the
presence of unknown reductants. Normalized by air volume, the fine PM
(PM2.5) generally makes more HOOH than the corresponding coarse PM
(PMcf, i.e., 2.5 to 10 μm), primarily because the mass
concentration of PM2.5 is much higher than that of PMcf. However,
normalized by PM mass, the coarse PM typically generates more HOOH than the
fine PM. The amount of HOOH produced by SJV PM is reduced on average by (78 ± 15)%
when the transition metal chelator desferoxamine (DSF) is
added to the extraction solution, indicating that transition metals play a
dominant role in HOOH generation. By measuring calibration curves of HOOH
generation from copper, and quantifying copper concentrations in our
particle extracts, we find that PBS-soluble copper is primarily responsible
for HOOH production by the Fresno PM. Extrapolating our results to expected
concentrations of PM-derived HOOH in human lung lining fluid suggests that typical daily
PM exposures in the San Joaquin Valley are unlikely to cause HOOH-mediated
acute health effects, but that very high PM events might lead to cytotoxic
levels of pulmonary HOOH. |
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