(K ow ) between 4 and 7, and show low very low solubility in water of a few μg L
À1 .
Pyrethroids are photosensitive and get easily hydrolysed; therefore their degradation
time for 50% of the substance (DT 50 ) – indicating persistence – is very low, below
60 days [21].
Organic contaminants include a wide variety of families. Some of them have been
considered persistent organic pollutants (POPs). The Stockholm Convention on
Persistent Organic Pollutants defined four factors that make a compound dangerous
and that qualify it as a POP [22]. These are the requirements a compound needs to
meet to be included in the list of the Stockholm Convention:
O
O
CH 3
CH 3
Cl
CH 3
F
F
F
O
O
CH 3
CH 3
CH 3
C
H 3
CH 3
CH 2
O
O
O
CH 3
CH 3
CH 3
C
H 3
N
N
O
O
CH
O
O
CH 3
CH 3
O
S
O
n
i
r
h
t
n
e
f
i
b
n
i
r
h
t
e
l
l
a
n
i
r
h
t
e
d
a
k
n
i
r
h
t
o
r
p
i
m
i
O
O
O
CH 3
C
H 3
Cl
Cl
O
O
O
CH 3
C
H 3
CH 3
CH 3
n
i
r
h
t
o
n
e
h
p
n
i
r
h
t
e
m
r
e
p
O
O
CH 3
CH 3
CH 3
C
H 3
CH 3
CH
O
O
O
CH 3
C
H 3
Cl
Cl
O
n
i
r
h
t
e
m
s
e
r
n
i
r
h
t
e
l
l
a
r
p
O
O
CH 3
C
H 3
C
H 3
C
H 3
N
O
O
O
O
CH 3
C
H 3
Cl
Cl
F
F
F
F
n
i
r
h
t
u
l
f
s
n
a
r
t
n
i
r
h
t
e
m
a
r
t
e
t
Fig. 2 Type I pyrethroids
Introduction to Pyrethroid Insecticides: Chemical Structures, Properties, Mode. . .
5