samples, destructive sampling and analyzing compounds in an
analytically complex biological matrix.
Temporal disparities in exposure and estimated risk were ob-
served in the Superfund area. Several studies have observed higher
PAH concentrations with increasing precipitation, ﬂows, and urban
runoff (Ko and Baker, 2004; Gasperi et al., 2005; Brown and Peake,
2006) and Stout et al. (2004) note that storm water is the greatest
contributor to sediment PAHs over time. However, our data dem-
onstrate an opposite tendency, where the dry season is associated
with higher water concentrations, higher exposure, and conse-
quently higher risk, in the Superfund area. Dilution does not ex-
plain the concentration and risk disparities between wet and dry
seasons in the Superfund area either. Unlike the Superfund sites,
upriver and downriver areas do not demonstrate seasonal varia-
tions. If the observed differences in the Superfund were due to
dilution, this should be a uniform effect in the river. One potential
explanation for the seasonal differences observed only within the
Superfund site, and especially at 7W, 6.5W and 3.5W, is that con-
taminant diffusion from sediments into overlying water is respon-
sible for high concentrations. The contamination may be from
riverbank sediments and higher wet season ﬂows could inhibit
groundwater movement into the river due to hydraulic pressure
and bank storage (Winter et al., 1998; Sower and Anderson,
2008). Another possible explanation is that higher summer tem-
peratures cause greater contaminant diffusion from the sediment
to the water column. Further investigation is required to elucidate
sources of seasonal disparities in PAH contamination in the Super-
A sediment cap over creosote contaminated sediments at RM
7E, installed prior to this study, was found to be effective in pre-
venting PAH contamination into the overlying water column
(Sower and Anderson, 2008) but did not diminish RM 7W high con-
centrations. The cause of the signiﬁcant difference observed be-
tween sites located in close proximity to one another, such as
RMs 7E, 7W and 8E, merits further study. It also highlights the
importance of considering spatial differences in risk on a small
scale, which can be achieved by taking PSD data into account in
While remediation of contaminated sites is desirable, few stud-
ies have assessed the potential impacts of dredging on exposure
and risk during and after remediation (Committee on Sediment
Dredging at Superfund Megasites, 2007). This study provided an
opportunity to evaluate the effects of dredging on PAH bioavail-
ability and potential human health risks from exposure. Prior to
capping, dredging at RM 6.3W removed signiﬁcant quantities
(>11 500 m
) of coal tar; however the area remains a higher risk
with higher freely-dissolved PAH concentrations than surrounding
areas, particularly in the dry season.
This study demonstrates an association between variable ﬂows,
sediment disturbance and freely-dissolved and, thus, bioavailable
contamination in the water column. Although the dredging pro-
duced a spike in exposure to PAHs, and a corresponding increase
in risk values, the duration of the effect was limited to the time
that it took to complete the operation. The short duration of the
disturbance would only be expected to have an immediate and
more substantial effect on aquatic organisms. Though ﬁsh kills
were observed within the containment area, none were observed
outside the barriers (Parametrix, 2006).
The site downriver from the Superfund megasite, RM 1E, is not
signiﬁcantly different in concentration from the Superfund sites.
While the Portland Harbor Public Health Assessment only sampled
within the Portland Harbor Superfund sites, our data demonstrate
that the downriver site has similar concentrations and could pose
similar health risks. Seasonal and spatial information like this
could be useful to public health ofﬁcials when constructing a
health assessment or determining where to post warning signs.
PSDs provide spatially and temporally resolved contaminant
exposure information that, as demonstrated here, can be incorpo-
rated into risk assessment models. This study revealed signiﬁcant
spatial and temporal differences in risk that would not have been
elucidated in a traditional risk assessment, such as the Portland
Harbor Public Health Assessment. Although it is clear that humans
do not consume PSDs, their application as a biological surrogate in
risk assessment models has the potential to provide speciﬁc spatial
and temporal contaminant exposure information that can assist
public health professionals in accurately evaluating human health
risks. Furthermore, using PSDs for risk assessment has the advan-
tages of larger sample size, non-destructive sampling and compa-
rability across studies. PSDs provide biologically relevant
exposure data for risk assessment that could be used when organ-
ism data is not available or to complement, and further reﬁne,
other measures of exposure.
This project was supported in part by award numbers P42
ES01645 and P42 ES00210 from the National Institute of Environ-
mental Health Sciences. Further funding was provided by the
SETAC Chemistry Early Career for Applied Ecological Research
Award sponsored by the American Chemistry Council to K.A.A
and MFGSC Grant E3003850. The content is solely the responsibil-
ity of the authors and does not necessarily represent the ofﬁcial
views of the funding agencies. We appreciate assistance from R.
Grove of USGS, Corvallis, OR, and D. Sethajintanin, E. Johnson, W.
Hillwalker, L. Quarles, K. Hobbie and A. Perez from OSU.
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Please cite this article in press as: Allan, S.E., et al. Estimating risk at a Superfund site using passive sampling devices as biological surrogates in human
health risk models. Chemosphere (2011), doi:10.1016/j.chemosphere.2011.06.051