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for children <19 years old. Children <5 years old were particularly sensitive to the
Fe component of PM
2.5
for respiratory admissions, with signifi cant associations at
both 1- and 3-day lags.
Hirshon et al. (
2008
) correlated Zn levels reported from the STN network sam-
pler located at the Baltimore “Supersite” in Greater Baltimore, and urgent health
care visits for children 0-17 years old. The authors reported that “medium” levels
of Zn (8.63-20.76 ng/m
3
) on the previous day were associated with greater than 1.2
times the risk of pediatric asthma problems that day than if “low” levels of Zn
(<8.63 ng/m
3
) occurred on the previous day; but, “high” levels of Zn (>20.76 ng/m
3
)
on the previous day were associated with only a 1.16 times higher risk of asthma
emergency department (ED) visits and hospitalization. There were no signifi cant
associations between levels of Zn and same day emergency department admissions,
and no consistent “dose-response” relationships in this study.
3.2.3
General Population
Ostro et al. (
2008
) evaluated differences in cardiovascular mortality for whites and
Hispanics associated with PM
2.5
metals. Changes in concentrations of Cu, Fe, K and
Ti (but not Mn, Ni, V and Zn) were associated with increased risk for the categories
of non-high school graduates and being Hispanic. A 2-3% increase in risk of car-
diovascular mortality was associated with an IQR increase for Cu for Hispanics, and
a 1-2% increase in risk of cardiovascular mortality associated with an IQR increase
of Zn for whites. Increased risks of 3% and 5% for cardiovascular mortality were
associated with IQR increases in Fe and Zn in people who did not graduate from
high school. IQR values for these metal components ranged from 7 ng/m
3
for Cu to
99 ng/m
3
for Fe (see Table
4
).
In a study conducted by Burnett et al. (
2000
) regression models and principal
components analysis were used to evaluate daily mortality rates and particulate- and
gas-phase air pollutants in eight Canadian cities. A positive and statistically signifi -
cant relationship was found for PM
2.5
Zn, Ni, and Fe and mortality from lag 1 day
data. Both single and multi-pollutant models showed similar percent increases for
Zn, Fe, and Ni in daily non-accidental deaths. Statistically signifi cant relationships
were not found for As, Cr, Cu, Mn, Se, Ti, and V.
Laden et al. (
2000
) correlated daily all-causes mortality in six U.S. cities with
PM
2.5
metal concentrations from crustal (soil), mobile sources, and coal combustion
sources using Poisson regressions in a generalized additive model. The authors
reported that a 10
g/m
3
increase in PM
2.5
from mobile sources and the same incre-
mental increase in PM
2.5
from coal combustion accounted for a 3.4% and 1.1%
increase in daily mortality, respectively. In models with all individual elements
included simultaneously, sulfur, Pb and Ni were found to be signifi cantly associated
with total mortality across all cities. The authors state that V and Fe were statisti-
cally associated with increases in daily mortality when evaluated separately, but
were no longer signifi cant if modeled simultaneously with sulfur, Ni and Pb.
Lippmann et al. (
2006
) investigated associations between PM metals and cardiovas-
cular outcomes across 60 cities in the National Mortality and Morbidity Air Pollution
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