Report from the Sub-comittee on the environment and health

O<strong>the</strong>r risk groups
104
of <strong>the</strong> differences in pesticide-related health risks between children and
adults. Differences in exposure were generally a more important cause of
differences in risk than age-related differences in <strong>the</strong> way <strong>the</strong> substances
act in <strong>the</strong> organism. However, <strong>the</strong> council found that, among o<strong>the</strong>r
things, effects on neurological and immunological development
processes were insufficiently clarified.
With respect to an increased effect with <strong>the</strong> same exposure to pesticides,
<strong>the</strong>re is agreement that foetuses and children are a special risk group
(Goldman 1995; Reigart 1995). As stated in <strong>the</strong> above-mentioned report
<strong>from</strong> NRC, <strong>the</strong>re are both qualitative and quantitative differences
between children and adults with respect to <strong>the</strong> toxicity of chemical
substances, including pesticides (National Research Council 1993). The
report gives examples, mostly concerning medical drugs, where children
are more or less sensitive to <strong>the</strong> individual substances. These differences
result <strong>from</strong> <strong>the</strong> fact that <strong>the</strong> substances are degraded at a different rate in
<strong>the</strong> body in children than in adults and <strong>from</strong> <strong>the</strong> greater or lesser toxicity
of <strong>the</strong> degradation products compared with <strong>the</strong> parent substance. The
qualitative differences in toxicity are due to exposure in particularly
sensitive periods in early development, when exposure to a toxic
substance can permanently change <strong>the</strong> structure or function of an organ
system. The quantitative differences in toxicity between children and
adults are due partly to age-related differences in absorption, metabolism,
detoxification and excretion of <strong>the</strong> environmentally foreign substances
and partly to differences in size, not fully developed biochemical and
physiological functions and variations in <strong>the</strong> composition of <strong>the</strong> body
(water, fat, protein and mineral content), all of which can affect <strong>the</strong>
degree of toxicity. Since new-born infants are <strong>the</strong> group that differ most
<strong>from</strong> adults, anatomically and physiologically, <strong>the</strong>y must be regarded as
having <strong>the</strong> most pronounced quantitative differences in sensitivity to
pesticides. The report found that quantitative differences in toxicity
between children and adults were normally lower than a factor of 10.
With reference to <strong>the</strong> foregoing, <strong>the</strong> US Environmental Protection
Agency (US-EPA) estimates that children constitute a special risk group.
Accordingly, in individual cases in <strong>the</strong> USA, an extra uncertainty factor
of 100 is used when setting maximum limit values in connection with
risk analyses that are based on animal tests and that are not deemed to
throw sufficient light on <strong>the</strong> special situation of children. Examples of
such substances and <strong>the</strong> related uncertainty factors (in brackets with <strong>the</strong>
year) are: heptachlor (200 in 1990), triazophos (500 in 1990), fentin (200
in 1970; 500 in 1991), abamectin (500 in 1992), amitrol (provisional
uncertainty factor of 1000 in 1993), phosalon (200 in 1993) and
propylene thiourea (metabolite of probineb, 1000 in 1993).
Pregnant women, <strong>the</strong> elderly and persons with a poorly functioning
immune system are o<strong>the</strong>r groups that must be presumed to be particularly
at risk with respect to health effects <strong>from</strong> exposure to pesticides.
6.2.3 Exposure of <strong>the</strong> population
The general population can be exposed to pesticides through <strong>the</strong>ir intake
of pesticide residues in food and via drinking water or through use of
pesticides in and around <strong>the</strong> home, schools, offices, public parks and
farms (drift and evaporation). Exposure can also occur through accidents,