Report from the Sub-comittee on the environment and health

Kartofler = Potatoes
Andre grøntsager = O<strong>the</strong>r vegetables
fra xx pesticider = <strong>from</strong> xx pesticides
Uncertainties and
reservations
Absorption and excretion
of pesticides
Metabolism
Bioaccumulation
Authorisation and risk
assessment of pesticides
with a view to public
health
It must be remembered that <strong>the</strong> calculations are encumbered with
relatively great uncertainty. That applies to <strong>the</strong> determination of <strong>the</strong>
residues of <strong>the</strong> individual pesticides and to <strong>the</strong> dietary data used. At <strong>the</strong>
same time, <strong>the</strong> residues used are based on a cautious evaluation, which
means that <strong>the</strong> values must be assumed to lie above <strong>the</strong> real content. The
result is thus an over-estimation of <strong>the</strong> intake of both Danish and
imported products. There is also a big variation in <strong>the</strong> data used for
intake of diet. This variation is due partly to uncertainty in <strong>the</strong>
determination of <strong>the</strong> mean intake of <strong>the</strong> individual food products and
partly to a variation as a consequence of different eating habits in <strong>the</strong>
population. Taken overall, <strong>the</strong> intake of <strong>the</strong> individual food products
shown in table 6.5 can vary by several hundred per cent <strong>from</strong> one person
to ano<strong>the</strong>r.
However, it must be stressed that a person with a relatively large
consumption of one type of food will often have a smaller consumption
of o<strong>the</strong>r types, so variations in <strong>the</strong> total pesticide intake will not
necessarily vary to <strong>the</strong> same extent as <strong>the</strong> food consumption.
6.2.5 Determination of <strong>the</strong> effects of pesticides on <strong>the</strong> population
Uptake of pesticides takes place after oral intake and, to a lesser extent,
through inhalation or via <strong>the</strong> skin. Absorption via <strong>the</strong> lungs is normally
fast compared with <strong>the</strong> o<strong>the</strong>r exposure routes because of <strong>the</strong> thin alveolar
membrane and <strong>the</strong> ample blood flow. Absorption via <strong>the</strong> skin is often
slow, but for pesticides that are metabolised quickly in <strong>the</strong> liver, skin
exposure can be <strong>the</strong> main exposure pathway. With respect to exposure of
<strong>the</strong> foetus, it has been found in animal studies that certain pesticides –
particularly organophosphates and carbamats – can pass <strong>the</strong> placenta
(Salama et al. 1993).
Metabolism or biotransformation of <strong>the</strong> absorbed, biologically available
dose (<strong>the</strong> internal dose) determines how large a part reaches <strong>the</strong> target
organ. Almost all <strong>the</strong> chemical changes that pesticides undergo in <strong>the</strong>
body are due to special enzymes (Hayes, Laws 1991). The first stage in
<strong>the</strong> biotransformation normally takes place via microsomal enzymes,
which catalyse an oxidation or reduction reaction. These enzymes
include all <strong>the</strong> cytochromal P450-enzyme systems in <strong>the</strong> liver, which is
<strong>the</strong> main organ for biotransformation of chemicals. The degradation
products are normally less toxic and more easily eliminated than <strong>the</strong>
pesticide itself. However, for some pesticides, an activation takes place,
which can lead to <strong>the</strong> formation of more toxic metabolites.
Some pesticides that accumulate in <strong>the</strong> body’s fatty tissue have very long
half-lives. These so-called persistent substances are now banned. They
include <strong>the</strong> chlorinated pesticides, such as DDT and dieldrin.
According to an EU directive (91/414/EEC) on marketing of plant
protection products, a risk assessment of health and environmental
properties of <strong>the</strong> product must be carried out in connection with <strong>the</strong>
authorisation procedure. The magnitude of <strong>the</strong> real and <strong>the</strong> potential
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