Environmental Engineering Reference
In-Depth Information
metal composition of the samples made it diffi cult to defi ne the role of the individ-
ual metals in the infl ammatory response. On the other hand, the endotoxin content
of the PM samples was associated with the differences in response. Unlike the metal
doses, the endotoxin levels measured in this study were the same order of magni-
tude as the median for ambient air, 1.085 endotoxin/EU m
3
(95% CI 0.915-1.251),
reported by Carty et al. (
2003
) for Munich, Germany. This study (Schins et al.
2004b
) is unusual in that it accounted for the presence of endotoxin as a potential
contributor to the infl ammatory response.
Gerlofs-Nijland et al. (
2009
) investigated the potential contributions of transition
metals and polycyclic aromatic hydrocarbons (PAHs) to infl ammation and pulmo-
nary toxicity in spontaneously hypertensive rats instilled with extracts of PM from
the cities of Prague, Duisburg and Barcelona at a dose of 7 mg extract/kg body
weight of the animals. In some experiments, a chelating agent was added to the
extract prior to administration. Extracts of both fi ne and coarse PM from Duisburg
(highest metal content) signifi cantly increased in infl ammatory markers in
BALF. Chelated extracts still produced a signifi cantly greater infl ammatory response
than controls. When interpreting the results from these studies, it should be consid-
ered that these researchers also found positive correlations between PAHs and some
indicators of infl ammatory damage.
Happo et al. (
2008
) evaluated the toxicity of water-soluble and water-insoluble
coarse (PM
2.5-10
) and fi ne (PM
0.2-2.5
) particulate from six European cities having dif-
ferent airshed characteristics. C57BL/6J mice were instilled with 10 mg PM extract/
kg body wt, sacrifi ced at 4 or 12 h post-treatment and infl ammatory markers in
BALF were measured. Results were analyzed using Spearman's rank correlation.
The authors reported that dicarboxylic acids and transition metals (Ni and V) in
PM
2.5
had a positive correlation with infl ammatory indicators; secondary inorganic
ions (nitrate and ammonium) were negatively correlated with infl ammatory mark-
ers. None of the correlations were statistically signifi cant and the actual concentra-
tions of the individual metals in the PM mass were not given.
Comments on In Vivo Studies with Ambient PM
As a group, the seven studies reviewed in this section provide some limited evidence
for the role of metals in the infl ammatory response to ambient PM. Although the
general epidemiology literature suggests that fi ne particulate (PM
2.5
) is more
strongly associated with increases in morbidity and mortality from respiratory and
cardiovascular causes than coarse particulate, the ambient PM source samples avail-
able to the authors of these studies did not always allow evaluation of toxicity by
size fraction. In fact, the fi ndings of Schins et al. (
2004b
) are not consistent with the
hypothesis that fi ne PM is more active with regard to metals. It must also be empha-
sized that the doses of total PM and associated transition metals administered to the
animals in some of the studies reviewed above in this section were as much as four
orders of magnitude greater than humans are exposed to by breathing ambient air in
most areas of the U.S.
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