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Study (NMMAPS). These authors reported that daily cardiovascular mortality rates
were signifi cantly associated with Ni and V and that mortality risk coeffi cients were
high in areas where Ni and V concentrations were in the 95th percentile, versus those
areas where the Ni and V component concentrations were in the 5th percentile. No
signifi cant associations were reported for As, Cr, Cu, Fe, Mn, Se, or Zn.
Using Bayesian hierarchical regression models, Dominici et al. (
2007
) re-
analyzed the relationships between Ni and V and daily mortality from the NMMAPS
data previously evaluated by Lippmann et al. (
2006
). Dominici found that when
specifi c areas from New York City were excluded from the analysis, the effect of Ni
and V on mortality was no longer statistically signifi cant, indicating that the results
found by Lippmann et al. (
2006
) were affected by inclusion of these New York
Communities where the PM
2.5
Ni and V were 8.9 and 3.4 times higher than the aver-
age values found in the other study areas. Both Lippmann et al. (
2006
) and Dominici
et al. (
2007
) used NMMAPS mortality data (1987-1994 for Lippmann and 1987-
2000 for Dominici) that signifi cantly pre-dated the PM
2.5
speciation data for metals
(2000-2003 for Lippmann and 2000-2005 for Dominici). It is not clear how Ni and
V concentrations measured in the air 1-13 years
after
the time period of the mortal-
ity data can be effectively used to represent exposures during the previous time
period, and no evidence was presented to indicate that Ni and V concentrations
remained consistent across time. Lippmann et al. (
2006
) acknowledged that changes
in Clean Air Act Regulations between 1990 and 1995 might have led to a reduced
Ni concentrations. No accommodations were made in either the Lippmann et al.
(
2006
) or Dominici et al. (
2007
) studies to account for the possible reduced Ni and
V concentrations or the impact this might have on the results.
Franklin et al. (
2008
) evaluated associations between STN data for PM
2.5
metals
(see Table
4
) and mortality in 25 U.S. cities, adjusting for time spent indoors, socio-
economic factors, and the locations of the PM
2.5
monitors used in their analysis of
the data. The authors reported that higher proportions of Al, As, sulfate, Si and Ni
existed as individual components in the PM
2.5
; moreover, combinations of Al, sul-
fate and Ni averaged over 2 days were associated with an increase in non-accidental
deaths. No signifi cant associations were found for Cr, Fe, Mn, V, or Zn.
Using the same California PM metal data as in related studies, Ostro et al. (
2007
)
reported associations in general population mortality that were consistent across sea-
sons between Cu, Fe, Ti, V, and Zn, but not Mn or Ni (see Table
4
for concentrations).
All-cause mortality was associated most strongly with Cu at a 1-day lag. Cardiovascular
mortality was associated most strongly with Fe (2-day lag), Ti (1- and 2-day lag), and
Zn (3-day lag). An excess risk of 2.2% per IQR of Zn was found for cardiovascular
mortality at the 3-day lag. Respiratory mortality was most strongly associated with
Cu and Ti (3-day lag) and to a lesser extent with V and Zn (1-day lag).
3.2.4
Critical Comments on the Epidemiology Studies
A relatively small number of epidemiological studies were identifi ed, in which the
study design allowed for the correlation of morbidity and mortality with levels of
individual transition metals in ambient PM. The studies included in this review are
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