Environmental Engineering Reference
In-Depth Information
In Vivo Exposures to Metals in CAPs
The particulate fraction of ambient air can be concentrated while maintaining the
same proportions of constituents. Inhalation studies performed with the resulting
concentrated ambient particulates (CAPs) are representative of exposures to the
source air, only at higher concentrations of particulates. Since there are relatively
few particle concentrators in existence, the majority of studies with CAPs have been
conducted by researchers affi liated with institutions that have this technology, such
as the Harvard School of Public Health, University of North Carolina, or New York
University School of Medicine. We discuss six studies in this section that are of
similar design and were conducted to examine the cardio-pulmonary responses of
dogs (Clarke et al.
2000
and Wellenius et al.
2003
), rats (Batalha et al.
2002
;
Kodavanti et al.
2005
; and Saldiva et al.
2002
), or mice (Lippmann et al.
2006
).
Clarke et al. (
2000
) exposed healthy dogs to CAPs or fi ltered air for 6 h/day for
3 days using a paired experimental design. CAPs concentration factors ranged from
17 to 28, with considerable variability in the relative concentrations of metals over
the days of exposure. Samples of blood and BALF were analyzed for fi brinogen,
cell counts and protein levels. Responses were highly variable and there were no
signifi cant differences in BALF or blood parameters in controls or CAPs exposed
dogs compared to pre-exposure baseline levels. The authors suggested that pulmo-
nary infl ammatory responses, after ambient PM inhalation may not be a major
contributor to the morbidity and mortality reported in epidemiologic studies.
In a subsequent study, Wellenius et al. (
2003
) investigated the effect of CAPs
(concentration factor approximately 30 times ambient levels) on myocardial isch-
emia in a canine model of coronary artery occlusion. Six pairs of dogs were ran-
domly assigned to breathe CAPs or fi ltered air, followed by coronary artery
occlusion and electrocardiographic examination, for a total of 21 exposure cycles.
Exposure to CAPs as compared to fi ltered air was signifi cantly (mixed effects and
multivariate analysis) associated with indicators of myocardial ischemia during
occlusion. Although not a target metal for this review, the Pb concentration in CAPs
was signifi cantly associated with ischemic changes, but this fi nding may be an arti-
fact of multiple comparisons.
In companion studies, Batalha et al. (
2002
) and Saldiva et al. (
2002
) evaluated an
18-day exposure to CAPs at particulate concentrations ranging from 73.5 to 733.0
g/
m
3
(approximately 30 times ambient). The authors measured vasoconstriction of
small pulmonary arteries in normal rats and in rats with chronic bronchitis (Batalha
et al.
2002
) exposed to CAPs. Pulmonary infl ammation (Saldiva et al.
2002
) was
measured in healthy Sprague Dawley rats and in rats with chronic bronchitis exposed
to CAPs. Chronic bronchitis was induced by exposing the rats to SO
2
for 5 weeks
prior to conducting studies with CAPs. In the study by Batalha et al. (
2002
), normal
and bronchitic rats were exposed to CAPs or fi ltered air for 5 h/day for three con-
secutive days, and were then sacrifi ced 24 h after the fi nal exposure, after which the
lungs and blood vessels were examined for histological changes. Silicon was signifi -
cantly associated with vasoconstriction in both normal and bronchitic rats, but no
signifi cant associations were found for Ni (10-160 ng/m
3
) and V (ND to 260 ng/m
3
).
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