Report from the Sub-comittee on the environment and health

Results of <strong>the</strong> model
calculation, impacts on
algae and crustaceans
Probability of effects
206
environment is assumed to be low. They are <strong>the</strong>refore not included in <strong>the</strong>
model. The model takes into account <strong>the</strong> temperature-dependent
degradation of <strong>the</strong> pesticides. Spray drift constitutes not more than 1% of
<strong>the</strong> area dose at a distance of 2 metres in March-April, when <strong>the</strong> pond
reaches its maximum size. In practice, <strong>the</strong> transport via spray drift is
lower in <strong>the</strong> model owing to adjustment for <strong>the</strong> area and cross section of
<strong>the</strong> pond, and <strong>the</strong> wind is assumed to blow in one direction. The model
does not include transport of pesticides via rainwater or long-distance
atmospheric transport. It can be assumed that <strong>the</strong> surface run-off of
pesticides constitutes 0.2% of <strong>the</strong> pesticide pool <strong>from</strong> <strong>the</strong> nearest 2
hectares in <strong>the</strong> field during precipitation events of more than 10 mm per
day, as described in section 4.6.1.
The simulations show that, all else being equal, <strong>the</strong> use of pesticides in
winter cereals, potatoes, root crops and peas constitutes a major risk to
<strong>the</strong> flora and fauna in ponds. Less burdensome crops are spring cereal,
spring rape, maize and, to some extent, winter rape. The model predicts
that <strong>the</strong> critical pesticides for algae and aquatic plants (macrophytes) in
ponds are isoproturon, glyphosate, fenpropimorph, ethofumesate,
metamitron, pendimethalin, metribuzin, prosulfocarb, mancozeb, maneb
and clopyralid. Crustaceans and insects are largely equally sensitive, and
<strong>the</strong> simulated effects on crustaceans can in principle be considered to
apply to insects as well. The critical pesticides with respect to effects on
crustaceans and insects are esfenvalerate, propiconazol, pendimethalin,
metribuzin, prosulfocarb, mancozeb and maneb. If <strong>the</strong>re are no run-off
events within a growth season, <strong>the</strong> only source of load on <strong>the</strong> pond is
spray drift. The analyses show that this supply is only of importance in
<strong>the</strong> case of esfenvalerate, with a 6-9% reduction in daphnia biomass.
Assuming that <strong>the</strong> ponds in Denmark are distributed at random in <strong>the</strong>
land under cultivation, <strong>the</strong> average pesticide load on ponds is calculated
on <strong>the</strong> basis of <strong>the</strong> model's predictions concerning effects on individual
crops and <strong>the</strong> area covered by individual crops. The 0-scenario is not
included in <strong>the</strong> calculations because <strong>the</strong> probability of effects would be
close to 0% assuming that <strong>the</strong> precipitation's content of long-distancetransported
pesticides would not have any effect in ponds. The
calculation shows quite a considerable probability of effects in both <strong>the</strong>
2.34 and <strong>the</strong> 1.17 scenarios, see figure 10.10. The probability of more
than 10% inhibition of algae is about 85% in <strong>the</strong> 2.34 scenario and about
45% in <strong>the</strong> 1.17 scenario, about 20% in <strong>the</strong> 0.59 scenario and about 10%
in <strong>the</strong> 0.26 scenario.