Report from the Sub-comittee on the environment and health

42
mononitrophenols and o<strong>the</strong>r nitrophenols, which contribute to <strong>the</strong>
atmosphere’s content of <strong>the</strong>se substances. However, <strong>the</strong> use of DNOC as
a pesticide outside Denmark may also contribute to <strong>the</strong> content of
nitrophenol in <strong>the</strong> atmosphere.
The following specific conclusions can be drawn:
• The insecticide lindane has been detected as an example of a
presumed transboundary atmospheric transport of pesticides.
• The existing national monitoring of <strong>the</strong> content of pesticide chemicals
in precipitation is limited and <strong>the</strong>re is a lack of data that can be
combined with <strong>the</strong> meteorological data.
• There are no Danish in situ measurements of <strong>the</strong> content of pesticide
chemicals in <strong>the</strong> air in connection with spraying.
4.6 Exposure pathways
Exposure of both people and <strong>the</strong> environment can occur during handling
of pesticides, during and immediately after treatment and as a
consequence of dispersal in <strong>the</strong> environment. The extent to which
pesticides are dispersed depends on <strong>the</strong>ir physical and chemical
properties, environmental conditions, and <strong>the</strong> way <strong>the</strong>y are used. A
pesticide’s persistence should be understood to mean its durability in <strong>the</strong>
environment: substances with a long degradation time are said to have
high persistence. The environmental effects of pesticides are discussed in
chapter 5. Human exposure <strong>from</strong> intake of pesticide residues is described
in section 6.2. Exposure of <strong>the</strong> users of pesticides is dealt with in section
6.1. In <strong>the</strong> following we discuss <strong>the</strong> dispersal in <strong>the</strong> environment, which
is of fundamental importance both for <strong>the</strong> environment and for <strong>the</strong>
exposure of people. The following processes and dispersal pathways are
described:
• surface run-off
• spray drift
• volatilisation
• degradation and leaching of pesticides
• filling and washing sites
4.6.1 Surface run-off
Pesticides can be transported with water running on <strong>the</strong> surface of <strong>the</strong>
ground. Surface run-off <strong>from</strong> sloping fields can carry both water-soluble
substances and substances that are adsorbed to particles of soil out into
watercourses and lakes. Particle-borne transport occurs during heavy runoff
of rainwater or melt water and soil erosion.
In a project in <strong>the</strong> Danish Environmental Protection Agency’s Pesticide
Research Programme (Felding et al. 1997), <strong>the</strong> surface run-off of two
relatively water-soluble herbicides (mechlorprop and dichlorprop) and a
sparingly water-soluble insecticide (alfacypermethrin) was studied during
two growth seasons (1992-1993). The field had an average gradient of
12% and was used for winter wheat in both years.