154 
chlorpyrifos) and (Barrett et al., 2000). An overview of the lowest values of prolonged 
acute toxicity of chlorpyrifos-ethyl for aquatic organisms is shown in Table 52. Up to 
now, no data is available on the chronic toxicity of chlorpyrifos to organisms in the 
marine environment which are exposed to low concentrations for several years. 
Table 52: Survey of lowest value of prolonged toxicity of chlorpyrifos-ethyl to aquatic organisms. 
Aquatic organism 
Species 
Value/period [d] 
Cone. [pg/L] 
Algae 
Scene demus subspicatus 
NOEC/4 
27.5 
Crustacean 
Mysidopsis bahia 
NOEC/35 
0.005 
Fish 
Pimephales promelas 
NOEC/30 
0.012 
Data from: (Data sheet on chlorpyrifos-ethyl) 
Environmental concentrations of chlorpyrifos-ethyl in different environmental samples 
are shown in Table 53. Concentrations on the order of of 0.4-0.9 ng/L have been found 
in rain water (TNO rapport, 2002). A detailed estimation of chlorpyrifos-ethyl 
deposition in surface and ground water is provided in a drinking water assessment by 
the environmental fate and effects division (Barrett, 1998). A study by the National 
Oceanic and Atmospheric Administration (Johnson et al., 1999) yields data on 
chlorpyrifos-ethyl concentrations in marine sediments and marine biota (Table 53). 
Table 53: Overview of chlorpyrifos-ethyl concentrations in water samples, sediments, and biota. 
Sample 
Sampling 
location 
Sampling date 
Concentration 
[ng/L]/[pg/kg dry 
wt] 
Limit of 
detection [pg/kg] 
Rain water 
Netherlands 
2000/2001 
0.9/0.4 a 
- 
Surface water 
US 
1995 
130 c 
4 
Ground water 
US 
1998 
36 c 
4 
Marine sediment 
US 
1994-1997 
0.84-5.68 d 
0.25 
Mussel tissue 
US 
1994-1997 
4.18-52.92 d 
0.25 
Data from: a (TNO rapport 2002), c (Barrett, 1998), d (Johnson et al., 1999) 
The major route of dissipation appears to be a slow aerobic and anaerobic degradation 
and photolytic degradation in soil to 3,5,6-trichloro-2-pyridinol (TCPy)(Figure 24) as