Report from the Sub-comittee on the environment and health

concerning relationships between dosage and concentration of pesticides
in <strong>the</strong> water samples analysed.
The following specific conclusions can be drawn:
• The pesticides detected in soil and drain water are often <strong>the</strong> same as
are detected in <strong>the</strong> aquifers, see section 4.1.
• The concentrations of pesticides detected in soil and drain water
exceed <strong>the</strong> limit value for drinking water more frequently than in <strong>the</strong>
groundwater analyses. Many of <strong>the</strong> pesticides detected are now
banned in Denmark, but were permitted at <strong>the</strong> time of <strong>the</strong> analyses.
• Owing to limited data, it is not deemed warranted to draw conclusions
concerning relationships between dosage in <strong>the</strong> field and
concentration of pesticides in drain and soil water.
• Assuming that <strong>the</strong> extent of <strong>the</strong> catchment area is known and that <strong>the</strong>
pesticides used in <strong>the</strong> area are known, a drain water analysis gives an
idea of whe<strong>the</strong>r used pesticides or <strong>the</strong>ir degradation products can
reach <strong>the</strong> groundwater. However, <strong>the</strong> results depend on <strong>the</strong> local
conditions and <strong>the</strong> wea<strong>the</strong>r, and it is not possible to carry out a mass
flow analysis that describes <strong>the</strong> fate of <strong>the</strong> pesticides in time and
space.
• Lysimeter studies and laboratory analyses of radioactively labelled
pesticides and degradation products in undisturbed columns of soil
can be suitable tools for judging <strong>the</strong> risk of leaching in connection
with <strong>the</strong> use of pesticides in different soils.
• Both <strong>the</strong> level of concentration and <strong>the</strong> frequency of detections are
highest in clayey soils. However, <strong>the</strong> data are limited and can be
improved with supplementary studies.
4.5 Pesticides in rainwater
As found by Felding (1998a), <strong>the</strong>re have been relatively few studies in
Denmark. In a cooperative project under <strong>the</strong> auspices of <strong>the</strong> Nordic
Council of Ministers, rainwater samples were collected <strong>from</strong> 2 localities
in Denmark – Ulfborg Plantation 10 km <strong>from</strong> <strong>the</strong> west coast of Jutland,
and Gadevang near Gribskov, a forest in North Zealand – <strong>from</strong> 1992 to
1994. The analyses covered 10 pesticides: propiconazole, prochloraz,
lambda-cyhalothrin, cypermethrin, esfenvalerate, deltamethrin, atrazine,
mechlorprop, dichlorprop and MCPA. Only <strong>the</strong> phenoxy acids were
detected, and <strong>the</strong> highest concentrations found were just under 0.4
microgramme per litre (Kirknel et al. 1997). The concentrations found
were very small in relation to <strong>the</strong> dosage in field spraying. The effects of
pesticides in rainwater are assessed in section 5.2.
In a current project, samples of precipitation are being collected <strong>from</strong>
three Zealand localities: Gadevang, Gisselfeld and Lorup. The samples
are analysed for <strong>the</strong> phenoxy acids: MCPA, mechlorprop and
dichlorprop, and for <strong>the</strong> herbicide isoproturon. The highest
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