Report from the Sub-comittee on the environment and health

Setting up a gross list with
a view to reviewing
pesticide leaching
150
included in <strong>the</strong> AF index. Major international studies indicate that
pesticide consumption, in particular, and to some extent also KOC, are of
significance for <strong>the</strong> occurrence in newly formed groundwater, whereas
DT50 does not seem to have any significant correlation with field data.
The fact that <strong>the</strong> Hasse diagram includes <strong>the</strong> dosage (consumption at
field level) and adsorption to soil (measured as KOC) is an attempt to base
<strong>the</strong> rankings on <strong>the</strong> results of <strong>the</strong>se studies.
There is thus considerable uncertainty about <strong>the</strong> rankings set up. This is
due particularly to <strong>the</strong> fact that leaching of pesticides to <strong>the</strong> groundwater
depends on factors that cannot be described by simple indices – for
example, extreme climatic conditions and seepage through cracks in <strong>the</strong>
soil (preferential flow). However, <strong>the</strong> results of <strong>the</strong> different ranking
methods can be used to draw up a gross list of <strong>the</strong> pesticides singled out
as problematical using <strong>the</strong> different methods. The gross list, which
comprises 35 pesticides, is shown in table 8.2. It is important to note that
<strong>the</strong> list is relative, i.e., it primarily compares substances with each o<strong>the</strong>r
and does not directly indicate substances as problematical in relation to
<strong>the</strong> groundwater.
Table 8.2
Gross list of pesticides singled out in three ranking methods as
potentially leachable in classes given as high (h) or low (l). Active
substances with potentially high leachability in all three methods are
denoted hhh, in two methods, lhh, hlh or hhl, and in one method, llh, lhl
or hll. Active ingredients with low leachability are denoted lll.
AF index a GUS index b
Hasse
diagram c
Class log(AF) d,Koc
l/kg p factor
2,4D hhh -1 S 0.97
clopyralid hhh -2 S 1
metaldehyde hhh -1 S 0.99
dicamba hhh -3 S 1
metabenzthiazuron hhh -3 S 1
fluroxypyr hhh -3 S 1
isoproturon hhh -3 S 1
bentazone hhh -4 S 0.96
carbofuran hhh -5 S 1
difenzoquat hhh -5 S 1
mechlorprop-P hhh -5 S 1
MCPA hhh -6 S 1
metsulfuron-methyl hhl -1 S 0.39
flamprop-M-isopropyl hhl -2 S 0.87
metribuzin hhl -4 S 0.88
triasulfuron hhl -1 S 0.81
ethofumesate hhl -6 S 0.76
haloxyfop-ethoxyethyl hhl -2 S 0.79
imidacloprid hhl -1 S 0.58
fenitrothion hlh -9 M 0.99
terbuthylazine hlh -9 M 0.94
pirimicarb hhl -7 S 0.64
azoxystrobin hll -8 M 0.76
isoxaben hll -8 M 0.27
tebuconazole hll -3 M 0.56
dimethoate llh -22 I 0.97
metamitron llh -19 M 0.95
chlormequat-chloride (CCC) llh -45 I 1