 |
| Titel |
Gaseous VOCs rapidly modify particulate matter and its biological effects – Part 2: Complex urban VOCs and model PM |
| VerfasserIn |
S. Ebersviller, K. Lichtveld, K. G. Sexton, J. Zavala, Y.-H. Lin, I. Jaspers, H. E. Jeffries |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 24 ; Nr. 12, no. 24 (2012-12-21), S.12293-12312 |
| Datensatznummer |
250011693
|
| Publikation (Nr.) |
 copernicus.org/acp-12-12293-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
This is the second study in a three-part study designed to demonstrate dynamic
entanglements among gaseous organic compounds (VOCs), particulate matter (PM),
and their subsequent potential biological effects. We study these entanglements
in increasingly complex VOC and PM mixtures in urban-like conditions in a large
outdoor chamber, both in the dark and in sunlight. To the traditional chemical
and physical characterizations of gas and PM, we added new measurements of
gas-only- and PM-only-biological effects, using cultured human lung cells as
model living receptors. These biological effects are assessed here as increases
in cellular damage or expressed irritation (i.e., cellular toxic effects) from
cells exposed to chamber air relative to cells exposed to clean air. Our
exposure systems permit side-by-side, gas-only- and PM-only-exposures from the
same air stream containing both gases and PM in equilibria, i.e., there are no
extractive operations prior to cell exposure for either gases or PM.
In Part 1 (Ebersviller et al., 2012a), we demonstrated the existence of PM "effect
modification" (NAS, 2004) for the case of a single gas-phase toxicant
and an inherently non-toxic PM (mineral oil aerosol, MOA). That is, in the
presence of the single gas-phase toxicant in the dark, the initially non-toxic
PM became toxic to lung cells in the PM-only-biological exposure
system. In this Part 2 study, we used sunlit-reactive systems to create a large
variety of gas-phase toxicants from a complex mixture of oxides of nitrogen and
54 VOCs representative of those measured in US city air. In these mostly day-long
experiments, we have designated the period in the dark just after injection (but
before sunrise) as the "Fresh" condition and the period in the dark after sunset
as the "Aged" condition. These two conditions were used to expose cells and to
collect chemical characterization samples. We used the same
inherently non-toxic PM from the Part 1 study as the target PM for "effect
modification". Fortunately, in the absence of "seed particles", the complex
highly-reactive VOC system used does not create any secondary aerosol in
situ. All PM present in these tests were, therefore, introduced by injection of MOA to
serve as PM-to-be-modified by the gaseous environment. PM addition was only done
during dark periods, either before or after the daylight period. The
purpose of this design is to test if a non-toxic PM becomes toxic in initially
unreacted ("Fresh"), or in reacted ("Aged") complex VOC conditions. To have a
complete design, we also tested the effects of clean air and the same VOC
conditions, but without introducing any PM. Thus, there were six exposure
treatment conditions that were evaluated with the side-by-side, gas-only- and
PM-only-effects exposure systems; five separate chamber experiments were
performed: two with clean air and three with the complex VOC/NOx
mixture.
For all of these experiments and exposures, chemical composition data and
matching biological effects results for two end-points were compared. Chemical
measurements demonstrate the temporal evolution of oxidized species, with a
corresponding increase in toxicity observed from exposed cells. The largest
increase in gas-phase toxicity was observed in the two "Aged" VOC exposures. The
largest increase in particle-phase toxicity was observed in the "Aged" VOC
exposure with the addition of PM after sunset. These results are a clear
demonstration that the findings from Part 1 can be extended to the complex urban
oxidized environment. This further demonstrates that the atmosphere itself
cannot be ignored as a source of toxic species when establishing the risks
associated with exposure to PM. Because gases and PM are transported and
deposited differently within the atmosphere and lungs, these results have
significant consequences. In the next (and final) part of the study, testing is
further applied to systems with real diesel exhaust, including primary PM from a
vehicle operated with different types of diesel fuel. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|