Report from the Sub-comittee on the environment and health

Ranking with respect to
groundwater pollution
The sub-committee’s
recommendations
concerning ranking with
respect to groundwater
pollution
224
1. scientific experts to set <strong>the</strong> limit for what can be predicated and
pinpoint what cannot be elucidated
2. an administrative instance to decide what can be operationalised
3. political decision-makers, i.e. non-experts, to make <strong>the</strong> final decision
on behalf of <strong>the</strong> public on <strong>the</strong> basis of trust in <strong>the</strong> scientific knowledge
and ethical and political considerations.
The sub-committee also wishes to draw attention to <strong>the</strong> fact that <strong>the</strong> limit
values used in <strong>the</strong> above-mentioned examples are based on <strong>the</strong> currently
achievable analytical detection limits. This means that <strong>the</strong> limit values
will be continuously adjusted downwards towards zero in step with <strong>the</strong>
technological development. The sub-committee wishes to point out that
this could ultimately lead to a total ban on <strong>the</strong> use of pesticides in
Denmark.
11.7 The sub-committee’s conclusions and recommendations
concerning ranking
The sub-committee concludes that it is not possible, with <strong>the</strong> existing
simple methods, to rank pesticides clearly with respect to <strong>the</strong>ir ability to
leach to <strong>the</strong> groundwater. However, it is possible, using four different
methods, to set up a gross list covering 35 of <strong>the</strong> authorised substances.
The substances on this gross list should be assessed more closely, using
ma<strong>the</strong>matical models, <strong>the</strong> latest knowledge and <strong>the</strong> results of
measurements.
In <strong>the</strong> years ahead, current research programmes will provide more
knowledge about <strong>the</strong> basic problems, and steps already in progress to
improve groundwater monitoring and early warning of <strong>the</strong> risk of
leaching pesticides to <strong>the</strong> groundwater will increase safety.
The sub-committee wishes to point out that, for improved risk
assessment, more work is needed to clarify <strong>the</strong> processes governing <strong>the</strong>
transport of pesticides to <strong>the</strong> groundwater and in aquifers, and greater
understanding must be developed of <strong>the</strong> spatial variation in <strong>the</strong>
parameters governing this transport. As results come in <strong>from</strong> <strong>the</strong>
constantly growing number of both national and international studies,
decision-making tools should be developed on <strong>the</strong> basis of statistically
documented relations for potential leaching of pesticides with a view to
generalising <strong>the</strong> studies to uninvestigated areas and pesticides. In this
connection, <strong>the</strong> sub-committee recommends greater use of ma<strong>the</strong>matical
models (e.g. MACRO) in <strong>the</strong> assessment of <strong>the</strong> risk of leaching of
pesticides and fur<strong>the</strong>r work on evaluating <strong>the</strong>ir validity. In this
connection, <strong>the</strong>re is a particular need to procure <strong>the</strong> necessary geological
and substance-specific data. The possibility of developing simple
stochastic (probabilistic) models should be looked into.
The sub-committee recommends that <strong>the</strong> gross list set up with a view to
reassessment of pesticide leaching be included in recommendations on
substitution with less dangerous substances in <strong>the</strong> use situation. It also
recommends that new products be assessed in relation to <strong>the</strong> gross list
and in relation to any non-chemical, alternative methods.