Environmental Engineering Reference
In-Depth Information
3.3
Toxicology
3.3.1
Human Exposure Studies
Epidemiology study results have suggested that the metals content of ambient PM
may be associated with increases in the incidence of adverse cardio-respiratory out-
comes in the general population. Source factor analyses have correlated concentra-
tions and groupings of specifi c metals (particularly transition metals) in ambient air
masses with particulate sources such as coal or oil combustion, motor vehicle traf-
fi c, industrial complexes and agricultural soil. In particular, studies conducted in the
Utah Valley during the late 1980s (Pope
1989
,
1991
,
1992
) suggested a decrease in
respiratory illness during a 1 year period in 1987, when a local open-hearth steel
mill was temporarily shut down. During the shutdown period, the levels of PM in
the Utah Valley declined dramatically compared to the years preceding and follow-
ing the shutdown. Samples of ambient PM collected on fi lters during those years
were archived and have subsequently been used for human, animal and
in vitro
stud-
ies. The results reported from this natural experiment suggest that metals may be a
contributory factor in the toxicity of PM.
A logical progression from the epidemiology studies is to test the hypothesis that
the metal constituents in ambient PM play a role in the health effects. Dose-response
has been evaluated by correlating changes in response parameters with variations in
the levels and content of metals in ambient PM over time in the same or different
geographic locations, or by administering known levels of metals to human subjects.
The human studies reviewed in this section fall into three major categories that
are based on the source of exposure to PM metals and the effects measured: 1) indi-
cators of pulmonary function correlated with changes in the levels of metals in ambi-
ent PM or in CAPs; 2) indicators of cardiovascular function correlated with metals
in inhaled CAPs; and 3) changes in infl ammatory markers from inhalation of CAPs
or from PM extracts instilled directly into the lungs of volunteers. Where suffi cient
data were available, we compared the concentrations reported in the studies to the
mean ambient concentrations in US urban areas reported by STN 2008 concentra-
tions (Table
1
). The relevant fi ndings from studies in each of these categories are
summarized below. The average concentrations of metals in ambient PM are pre-
sented in Table
5
for those studies, in which this information was readily available.
Effects of PM Metals on Indicators of Pulmonary Function
The studies by Hong et al. (
2007
and 2010) and Roemer et al. (
2000
) correlated the
daily changes in peak expiratory fl ow (PEF) rates in grade school age children with
changes in levels of ambient PM
10
and/or PM
2.5
and associated metals. The two studies
by Hong and co-workers were conducted in Seoul, Korea; the latter study (Hong et al.
2010
) was conducted during the Asian Dust Storm of May-June 2007. The study
by Roemer et al. (
2000
) was part of a larger European initiative to evaluate
Pollution Effects on Asthmatic Children in Europe (PEACE), and correlated PEF
(Peak Expiratory Flow) and respiratory symptoms reported by children living in
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