Environmental Engineering Reference
In-Depth Information
industrialized and non-industrialized cities with levels of ambient PM and metals by
source (e.g., industrial, agricultural, etc.). Lagorio et al. ( 2006 ) attempted to correlate
levels of metals associated with particulate air pollution on changes in pulmonary
function parameters in adults with compromised lung and/or cardiovascular function.
Although all four of these studies employed changes in PEF or PEV (Peak
Expiratory Volume) as indicators of effect correlated to daily changes in levels of
ambient PM, the study designs and individual metals that were quantifi ed were suf-
fi ciently different as to make direct comparisons amongst studies challenging.
The two studies with Korean school children were of similar design, but yielded
seemingly confl icting conclusions. The fi rst study (Hong et al. 2007 ) with 43 chil-
dren (not specifi ed as asthmatic) reported a signifi cant reduction in the morning and
mean PEFs lagged 1 day after increases in PM 2.5 , with an estimated mean decrement
in PEF of −0.54 L/min per 1
g/m 3 PM 2.5 increase on the preceding day.
Concentrations of Mn and Pb in the PM 10 were signifi cantly associated with changes
in morning and mean PEF. Hong et al. ( 2010 ) conducted the second study with 110
children during the 2007 Asian Dust Storm, when concentrations of particulate were
very high (>130,000
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g/m 3 in Seoul); results were that PM 2.5 and PM 10 concentra-
tions were not associated with signifi cant decreases in PEF rates except in asthmatic
children, where the effect was strongest with PM 10 . The concentrations of many of
the PM 10 bound metals, including Cd, Mn, Pb and Zn (Table 5 ), were reportedly
associated with signifi cant decreases in PEF rates in the children (Hong et al. 2010 ).
In both studies, the daily measurements of PEF were self-reported and the
number of subjects was fairly small, which may limit statistical power. The second
study (Hong et al. 2010 ) seemed incongruous, because, whereas the authors indi-
cated signifi cant associations between decreases in PEF and several individual met-
als of anthropogenic origin, they found no difference in the effect for metals from
anthropogenic (As, Cd, Mo, Pb, Zn) vs. natural sources (Al, Ca, Fe, Mn, Si).
Because the 2010 study was conducted during the Asian Dust Storm of 2007, which
originated in desert regions to the west of Korea, it would have been more logical to
fi nd associations between metals in natural as opposed to anthropogenic sources, if
the metals were actually contributing to the reported changes in PEF.
The Korean studies identifi ed signifi cant associations between changes in con-
centrations of Mn and Pb and changes in PEF. Roemer et al. ( 2000 ) studied 1,208
asthmatic children divided among 17 panels based on city of residence in the coun-
tries of Sweden, Finland, the Netherlands, Germany, Poland, Hungary and Greece.
Changes in PEF and symptom prevalence were signifi cantly correlated with changes
in Si and Fe concentrations. As for the two studies by Hong et al. ( 2007 , 2010 ), the
study by Roemer ( 2000 ) had several limitations. Although the total number of sub-
jects was larger, it did not appear that individual-level characteristics potentially
related both to metal exposure and to respiratory conditions were collected or used
in the analysis. Symptoms were self-reported and thus potentially biased. Moreover,
other possible exposures to respiratory irritants and causes of the effects being mea-
sured were not well characterized. In particular, none of the four transition metals
identifi ed in the original hypothesis (Ni, Zn, V, and Fe) was found to be signifi cantly
associated with respiratory symptoms, and the range of Si and Fe concentrations in
urban and suburban locations had signifi cant overlap.
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