Environmental Engineering Reference
In-Depth Information
target metals of interest extracted from ambient PM by instillation, or were exposed
to known concentrations of metals in CAPs by inhalation for a specifi ed length of
time. These studies are the human equivalent of the
in vivo
animal studies that will
be reviewed in subsequent sections. Exposure levels of the target metals used in the
human exposure studies below are summarized in Table
5
.
Ghio and Devlin (
2001
) conducted a study to correlate clinical evidence of air-
way infl ammation with epidemiologic fi ndings of a reduction in respiratory ail-
ments during a 1-year period in 1987 when an open hearth steel mill in the Utah
Valley was temporarily closed, as compared to the adjacent years, 1986 and 1988,
when the mill was operating. Aqueous extracts of PM collected from the Utah
Valley in 1986, 1987, and 1988 containing a 500
g equivalent mass of Fe, Zn, Cu,
Pb, Ni, and V were instilled into the left bronchi of three groups of 8 non-smokers.
An equal volume of saline was instilled into the right bronchi to serve as a control.
Twenty-four hours after instillation of the PM extract, the same bronchial segments
were lavaged for analysis of the following indicators of infl ammation: total cell
counts, protein, albumin, fi bronectin, neutrophils, alpha-1-antitrypsin, fi brinogen,
IL-8, and TNF-alpha. Exposure to aqueous extracts of PM collected during the
years that the steel mill was operating produced greater infl ammatory response than
extracts of PM collected during the year that the mill was shut down. Aqueous
extracts from 1986 and 1988, when the mill was in operation, had higher
concentrations of Fe, Cu, Zn, Pb, and Ni, and produced signifi cantly greater reactive
oxygen species (ROS)—as measured by the thiobarbituric acid reaction products of
deoxyribose—than extracts from the 1987 PM. Because the chelating agent defer-
oxamine inhibited oxidant generation by all three extracts, the authors inferred that
transition metals in the extracts were the cause of the ROS. In a follow-up paper,
Ghio (
2004
) expanded the discussion of fi ndings from the bronchoalveolar lavage
fl uid (BALF) study and added a summary of results from an
in vitro
study, in which
human respiratory epithelial BEAS-2 cells were incubated with PM extracts from
the 3 years of interest, and in which the oxidative activity was determined. The
results of the
in vitro
studies corroborate the fi ndings from the human exposure
studies, suggesting that soluble transition metals in ambient PM play a role in
infl ammatory damage.
In a study similar to those of Ghio (
2001
), Schaumann and co-workers (
2004
)
conducted a study on 12 human volunteers to determine whether metal constituents
of ambient PM
2.5
may be related to increased prevalence of allergic asthma amongst
children residing in a German copper mining and ore-processing town (Hettstedt)
vs. children from a rural area of Germany (Zerbst). Concentrations of Cu and Zn
were much higher in PM from the smelter town of Hettstedt than from the rural
town of Zerbst. Each volunteer was instilled with 10 mL saline (right upper lobe of
the lung), 100
ʼ
ʼ
g suspension of PM from Hettstedt in 10 mL saline (middle lobe)
and 100
g suspension of PM from Zerbst in 10 mL saline (lingula of the left lung).
After 24 h, bronchiolar lavage fl uid was obtained and levels of the following infl am-
matory indicators were compared for the control and the two PM extracts: total cell
count, macrophages, monocytes, lymphocytes, neutrophils, ROS generation, IL-1,
IL-6, IL-8, TNF-alpha, albumin, and lactate dehydrogenase (LDH). PM extracts
ʼ
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