Report from the Sub-comittee on the environment and health

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help in <strong>the</strong> assessment of new substances or in actual reviews. It may also
be necessary to obtain EU agreement to such requirements. It will at any
rate take time before <strong>the</strong> desired data are available. Before <strong>the</strong>
requirements can be tightened, agreement must be reached on which data
are necessary and sufficient, and a procedure must be laid down for
procuring <strong>the</strong>m.
3) New decision-making tools based on statistical methods
Although ranking methods are based on a very simple understanding of
<strong>the</strong> process and <strong>the</strong>refore cannot stand alone in an assessment, major
studies indicate that <strong>the</strong>re is, in spite of everything, some relationship
between relatively simple parameters and <strong>the</strong> occurrence of pesticides
that is observed. Much of <strong>the</strong> observed variation in occurrence can in fact
be explained on <strong>the</strong> basis of relatively simple relationships (Koplin et al.
1998; Kreuger, Tornqvist 1998). As results come in <strong>from</strong> still more
studies (national and international), it is recommended that decisionmaking
tools be developed (simple ranking index) on <strong>the</strong> basis of
statistically documented relationships with a view to generalising <strong>the</strong>
studies to uninvestigated areas and pesticides. The possibility of
developing simple, stochastic (probabilistic) models should also be
looked into.
4) Better data for <strong>the</strong> deterministic models
The question has been raised of whe<strong>the</strong>r one could use model
calculations to rank authorised pesticides on <strong>the</strong> basis of <strong>the</strong>ir leaching
risk. The calculation of leaching by means of MACRO covers a range of
factors that are not taken into account in <strong>the</strong> simple indices – <strong>the</strong> relevant
dosage for a specific crop, plant cover, dosing time, Danish climatic
conditions (precipitation and temperature) and preferential flow for
structured soils. However, some factors have to be clarified before
MACRO can be used to rank <strong>the</strong> authorised pesticides:
• Quality-assured data have to be obtained for each pesticide’s
degradation and adsorption in different types and strata of soil,
toge<strong>the</strong>r with <strong>the</strong> dosage.
• It must be clarified how <strong>the</strong> uncertainty on <strong>the</strong> variables describing <strong>the</strong>
degradation and adsorption is to be assessed.
• Limit values must be defined.
• It must be clarified how representative <strong>the</strong> scenarios used by DEPA
are.
Ranking by means of MACRO does not directly include an assessment of
<strong>the</strong> extent to which metabolites are formed, which must be considered a
serious constraint.
Even if satisfactory data are obtained and o<strong>the</strong>r factors can be
satisfactorily clarified, ranking by means of MACRO cannot stand alone.
An integrated expert assessment will also be needed.