Environmental Engineering Reference
In-Depth Information
Table 6
Risk quotients for maximum 95th centile measured concentrations of CPY in surface
waters of the U.S. before and after 2001
Taxon Crustacea Insects Fish
HC5 (
μ
g L
−1
) 0.034 0.091 0.820
RQ for greatest annual 95th centile pre-2001 (0.056
μ
g L
−1
)
a
1.65 0.64 0.07
RQ for greatest annual 95th centile post-2001 (0.008
μ
g L
−1
)
a
0.24
0.09 0.01
a
See Sect.
2.1
and Fig.
3
in Williams et al. (
2014
) for the derivation of the greatest annual 95th
centile concentrations
4.1
Risks from Measured Exposures
Risks for CPY in surface waters
. There is a relatively large database of measured
concentrations of CPY in surface waters (see detailed characterization in Sect.
3.1
in Williams et al.
2014
). In almost all of these data sets, frequency of sampling was
too small to allow exposures to be characterized as 96-h time-weighted-mean con-
centrations for direct comparison to 96-h toxicity values. However, comparisons in
relation to changes in the use of CPY were possible. The greatest annual 95th cen-
tiles of concentrations measured in surfaces waters by the US Geological Survey
before and after the introduction of new labels in 2001 clearly shows the reductions
in exposures and risks that resulted from the changed use pattern (Fig.
6
and
Table
6
). Based on 95th centiles and the HC5, risks for fi sh in either period were
small. An extensive review of the toxicity screening data from 2004 to 2009 in
samples of surface waters of the Central Valley of California (Hall and Anderson
2012
) confi rmed that the reductions in concentrations of CPY after 2001 (see Sect.
4
in Williams et al.
2014
) were refl ected in reductions in the frequency of detection
of toxicity mediated by CPY.
Risks for CPY in sediments
. The toxicity of CPY in sediments in areas of intensive
use, has infrequently been reported in studies conducted recently (Sect.
2.1
).
Comparison of the 10-d LC
50
toxicity values for
H. azteca
and
C. dilutus
(Table
3
)
to the greatest concentration (58.6
g kg
−1
) measured in sediments (Sect.
3.2
in
Williams et al.
2014
) gave RQs of 0.15 and 0.16 for the two species. These RQs are
only slightly above the Level of Concern for non-endangered species (USEPA
2004
) and are consistent with toxicity testing of sediments from areas of intensive
use since 2000 (Sect.
2.1
).
μ
Risks from CPYO
. As discussed in a companion paper (Solomon et al.
2014
), CPYO
is formed from CPY in the environment and
in vivo
but has seldom been detectable in
surface waters (see Sect.
4
in Williams et al.
2014
). The National Water Quality
Assessment (NAWQA) database included results of 7,098 analyses for CPYO in sur-
face water samples between 1999 and 2012 (NAWQA
2012
). CPYO was detected in
16 samples (detection rate of 0.23%), and the greatest estimated concentration (i.e.,
>LOD but <LOQ) was 0.0543
g CPYO L
−1
. Similar results were found in the National
Stream Quality Accounting Network (NASQAN) database (NASQAN
2012
),
μ
Search WWH ::
Custom Search