Report from the Sub-comittee on the environment and health

32
It will be seen <strong>from</strong> table 4.10 that <strong>the</strong> frequency of pesticide finds and
<strong>the</strong> concentration of <strong>the</strong> pesticides are generally highest in agricultural
catchment areas with clayey soils. That is presumably due to <strong>the</strong> fact that
farmers on rich soil often farm more intensively and thus spray more
often and to <strong>the</strong> fact that pesticides are quickly transported to
watercourses via drains through cracks in <strong>the</strong> clayey soil. The fact that
pesticides have been detected in springs indicates specifically that
pesticides can be led to watercourses via groundwater. Fewer different
pesticides have been found in forest watercourses, but <strong>the</strong> herbicides that
are used in forests frequently occur in <strong>the</strong> watercourses. That applies
particularly to hexazinone. Many different pesticides have been detected
in urban watercourses, which cover both “urban watercourses” and
“mixed catchment areas”. Agricultural pesticides <strong>the</strong>refore also occur.
Dichlobenil, which is used as a universal herbicide and particularly its
metabolite, BAM (2,6-dichlorobenzamide), occur very frequently, both
in urban areas, agricultural areas and forest watercourses, see table 4.11.
Concerning BAM, readers are referred to section 4.1, where a similar
frequency in groundwater is described.
In most of <strong>the</strong> watercourses, many different pesticides are found at <strong>the</strong>
same time, which is of significance in <strong>the</strong> assessment of <strong>the</strong> effects on
flora and fauna in <strong>the</strong> aquatic environment, see section 5.3.
Table 4.11
Occurrence of metabolites (of a dichlobenil, b glyphosate, c atrazine) of
pesticides in watercourses, with a breakdown by type of catchment area.
The table shows <strong>the</strong> number of finds out of <strong>the</strong> total number of samples
and <strong>the</strong> concentration range in microgramme per litre. Dichlobenil and
atrazine may no longer be used in Denmark. The first studies were carried
out by DMU in 1989-1991. In 1994-1996, a major study was carried out in Funen
County. In 1996, <strong>the</strong> table includes data <strong>from</strong> several counties (Mogensen 1998).
Type of
catchment
area/Metabolite
2,6-dichlorobenzamide
(BAM) a
AMPA*, b
desethylatrazine
c
desisopropylatrazine
c
Urban area 5/5; 0.03-0.4 n.a. 3/5; 0.01-0.03 4/5; 0.01-0.1
Mixed
catchment area,
clay
46/54; 0.05-0.2 5/5; 0.1-0.5 n.d./57 n.d./57
Mixed
catchment area
5/5; 0.04-0.07 n.a. n.d./5 n.d./5
Clayey agric.
catchment area
63/72; 0.03-0.4 1/1; 0.5 6/72; 0.01-0.1 8/72; 0.01-0.2
Sandy agric.
catchment area
12/25; 0.01-0.01 n.a. n.d./25 n.d./25
Sandy/clayey
catchment area
8/10; 0.01-0.009 n.a. n.d./10 1/10; 0.02
Forest
watercourse
4/25; 0.08-0.5 n.a. n.d./25 n.d./25
Uncultivated
catchment area
n.d./5 n.a. n.d./5 n.d./5
Springs 3/12; 0.1-0.5 n.a. n.d./12 n.d./12
* = AMPA has been detected in <strong>the</strong> same samples as <strong>the</strong> parent compound
glyphosate. It is <strong>the</strong>refore likely that <strong>the</strong> metabolite comes <strong>from</strong> glyphosate, but o<strong>the</strong>r
sources cannot be excluded.
n.a. = not analysed
n.d. = not detected