Environmental Engineering Reference
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Table 4 Toxicity values for chlorpyrifos oxon in aquatic organisms
Test
item
Expos.
type
Species
Resp. a
Test sub.
Expos. (d)
Endpoint
μ
g L −1
Inc.
Medium
Coral
Acropora
millepora
Fert
Embryo
0.125
EC50
>30
A
S
Q
SW
Acropora
millepora
Meta.
Larva
0.75
EC50
0.39
A
S
Q
SW
Crustacea
Daphnia magna
Mort.
<24-h old
2
LC50
1.9
A
F
Y
FW
Fish
Lepomis
macrochirus
Mort.
46 mm
4
LC50
1.1
A
F
Y
FW
Amphibians
Rana boylii
Mort.
G32-44
4
LC50
>5
A
S
N
FW
(0.82
μ
g L −1 , Table 2 ), while that for L. macrochirus was less than that for CPY
(4.2
g L −1 , Table 2 ). Although CPYO is much more potent than CPY at the target
(AChE), the molecule is very labile in aqueous solution (discussed below).
μ
3.4
Evidence from Microcosms and Mesocosms
Chlorpyrifos has been the subject of a large number of studies in microcosms and
mesocosms (Table 5 ). Because the distinction between microcosms and mesocosms
is primarily semantic, they are referred to jointly as “cosms” in the following dis-
cussion. Data from cosms add several types of realism to assessment of the potential
effects of chemicals on aquatic organisms (Graney et al. 1995 ). They allow for more
realistic exposure scenarios because factors such as photolysis, microbial degrada-
tion and adsorption to aquatic plants and sediments (Giesy and Odum 1980 ; Graney
et al. 1989 ) are included. Cosms also include dynamic interactions between and
among species so that potential “ecosystem-level” effects can be evaluated, includ-
ing predator-prey interactions in the larger systems (Giesy and Geiger 1980 ). Early
cosm studies of CPY were reviewed by Leeuwangh ( 1994 ), Barron and Woodburn
( 1995 ), and Giesy et al. ( 1999 ). Since the publication of the Giesy et al. review,
results of several cosm studies of CPY have featured prominently in comparisons of
cosm studies, single-species laboratory toxicity tests, and regulatory benchmarks
across classes of insecticides (Brock et al. 2000 , 2006 ; Maltby et al. 2005 ; van
Wijngaarden et al. 2005b ). Several newer cosm studies have broadened the scope of
conclusions about chlorpyrifos effects on aquatic communities to a wider range of
locations and environmental conditions (Daam et al. 2008a , b ; López-Mancisidor
et al. 2008a , b ; van Wijngaarden et al. 2005a ; Zafar et al. 2011 ). The body of evi-
dence from cosm studies is consistent in supporting the conclusion that concentra-
tions of 0.1
g CPY L −1 or less cause no ecologically signifi cant effects on aquatic
communities.
μ
 
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