Environmental Engineering Reference
In-Depth Information
significant persistence in the environments of use. The geometric mean of half-life
values in water tested in the laboratory was 21 d. Half-lives in water in the presence
of sediments in the field were even smaller (geometric mean of 5 d). These are less
than the trigger values of 60 d for POPs. Geometric mean half-lives in soil tested
under laboratory and field conditions had geometric means of 32 and 22 d, respec-
tively, both of which are less than the 180 d trigger. The geometric mean DT
50dis
s for
CPY in sediments tested in the laboratory and microcosms was 39 d, which is less
than the trigger value of 180 d.
Geometric means of values for BCF, BAF, and BSAF measured in the laboratory
(assumed to be equivalent, Sect.
5
, and Table
11
) and the field were 848 and 935,
respectively, all of which were less than the trigger value of 5,000. Studies of tro-
phic magnification of CPY in the field were not found in the literature but, based on
food-chain magnification measured in model ecosystems with
14-
C-labelled material
(Metcalf and Sanborn
1975
), CPY does not magnify to the same extent as any of the
currently identified POPs that were also tested.
The criterion for toxicity, “significant adverse effects”, used to classify chemi-
cals a POP, is somewhat vague (Solomon et al.
2009
) in that specific numerical
criteria are not provided. All pesticides are toxic to some organisms; otherwise they
would not be used. However, in the context of POPs and LRT, adverse effects are
more properly interpreted as ecologically significant outcomes on survival, growth,
development, and reproduction in organisms well outside the boundaries of the site
of application. Based on the conclusions of several of the companion papers, CPY
does not exceed the trigger for “significant adverse effects” in or outside the regions
of use (Cutler et al.
2014
; Giddings et al.
2014
; Moore et al.
2014
).
The half-life of CPY in the atmosphere of 1.4 d does not exceed the trigger value
of 2 d for LRT. CPY is found at distances from areas of application, and even in
remote locations (Sect.
2.1
); but the concentrations in air (Table
1
), rain and snow
(Table
2
), aquatic and terrestrial media (Table
3
), and biota (Table
4
) are small and less
than the threshold of toxicity for aquatic organisms and birds (Giddings et al.
2014
;
Moore et al.
2014
). Even assuming a longer half life of 3 d as was done earlier, the
concentrations at remote locations are low and do not approach toxicity thresholds.
Assessment of CPYO as a POP is complicated by the fact that it is a degradation
product of CPY and is usually present with the parent material in the environment
as well as during tests of effects of CPY. By itself, CPYO also does not exceed the
triggers for POPs (Table
12
) with respect to persistence in water, soil, and sediment
(Table
7
). No data were available for BCF of CPYO, but studies with ring-labelled
CPY provide equivalency for CPYO and it does not trigger the criterion for B.
Toxicity for CPYO is subsumed in that of CPY and it does not trigger “significant
adverse effects”. The half-life in air of approximately 11 h (Table
7
) is less than
25% of the LRT trigger of 2 d. In addition, replacement of the =S with =O in CPYO
increases polarity; CPYO is about 25-fold more water soluble, and has a K
OW
that is
100-fold smaller than that of CPY (Table
7
). Thus, CPYO will partition more into
water in the atmosphere (precipitation) and will be more likely to rain-out into sur-
face water or snow. Because of the greater electronegativity of the P-atom, CPYO
is more reactive than CPY and will undergo hydrolysis more rapidly than CPY; the
half-life in water (Table
7
) is approximately half that of CPY (Table
6
). Thus, CPYO
Search WWH ::
Custom Search