Report from the Sub-comittee on the environment and health

Hormone-mimicking
effects
Indirect effects of pesticides
on arthropods
64
poisoning and determine whe<strong>the</strong>r <strong>the</strong> death was due to poisoning, one
must be cautious about rejecting such a risk because of lack of records.
On <strong>the</strong> o<strong>the</strong>r hand, numerous field studies and laboratory tests indicate
that <strong>the</strong> vast majority of pesticides used legally in Denmark do not have
direct toxic effects in <strong>the</strong> concentrations in which <strong>the</strong>y occur in <strong>the</strong> field.
That also applies to most of <strong>the</strong> products used for seed dressing or as
granulate, since products that constitute a serious threat to fauna are no
longer sold on <strong>the</strong> Danish market.
Growing evidence has been found in <strong>the</strong> last few decades that man-made
substances can mimic hormones or <strong>the</strong> regulation of hormones in animals
and humans (Colborn et al. 1993). Such substances are often described as
hormone-like substances. They can have a big effect on reproduction and
<strong>the</strong> growth of organisms. Particular attention has been paid to substances
that mimic or affect <strong>the</strong> sex hormones, <strong>the</strong> so-called oestrogenous and
androgenous substances (Toppari et al. 1995). Manmade substances that
affect <strong>the</strong> hormone systems have been known for more than 40 years and
include previously and currently used pesticides and industrial chemicals.
Most of <strong>the</strong> knowledge in this area concerns humans and fish, whereas
little is known concerning terrestrial animals (Janssen et al. 1998). In <strong>the</strong>
case of pesticides, hormone-like substances have been found among <strong>the</strong>
now banned organochlorinated pesticides and organotin compounds.
Alkylphenols and alkylphenolethoxylates, which have been used as
coformulants in pesticide formulations, are examples of industrial
chemicals that can affect <strong>the</strong> hormone systems in animal tissue (Györkös
1996; Janssen et al. 1998). Tests with <strong>the</strong>se substances have been carried
out primarily on rats, mice and a few bird species. However, <strong>the</strong>
observed effects must be assumed also to apply to a large group of
mammals and birds. According to Janssen et al. (1998), corresponding
information is not available for o<strong>the</strong>r groups of animals. The pesticides
authorised for use today are not deemed to constitute a risk to terrestrial
fauna with respect to hormone-like effects. The amount of alkylphenols
and alkylphenolethoxylates used as coformulants in pesticides represents
less than 10% of <strong>the</strong> total use of this group of substances in Denmark.
Pesticides are <strong>the</strong> only group of products for which a phase-out of <strong>the</strong>se
substances has been prescribed before <strong>the</strong> year 2000. The phase-out has
largely been completed.
The purpose of treating crops with herbicides, fungicides and insecticides
is to remove <strong>the</strong> respective pests. Since <strong>the</strong> products generally have toxic
effects beyond what is intended, plants, fungi and insects must be
expected to be affected to a varying extent by spraying. This affects
organisms that prey on <strong>the</strong> affected species. It has also been proven that
herbivorous insects occur with much lower densities in areas treated with
herbicides (Potts, Vickerman 1974; Hald et al. 1988; Hald et al. 1994;
Reddersen et al. 1998) and that fungivorous insects are found in smaller
numbers in plots treated with fungicides (Hald et al. 1994; Reddersen et
al. 1998). In <strong>the</strong> case of predatory and parasitic insects, it can be difficult
to distinguish <strong>the</strong> direct effect <strong>from</strong> <strong>the</strong> indirect effect of insecticides on
<strong>the</strong>ir food. However, it has been found, for example, that <strong>the</strong> frequency
of ground beetles with empty stomachs is higher in fields treated with
insecticides than in untreated fields (Chiverton 1984).