Report from the Sub-comittee on the environment and health

Studies of frequency of
cancer
Reproductive toxicity
98
<strong>the</strong>m, with regard for <strong>the</strong> frequency or duration of <strong>the</strong> exposure. The
exposure data in all <strong>the</strong> studies are indirect and based on <strong>the</strong> parents’ job
titles, occupation and use of pesticides in <strong>the</strong> home. In addition, it must
be presumed that <strong>the</strong>re is some degree of recall bias concerning details
about <strong>the</strong> frequency and time of <strong>the</strong> use of pesticides in relation to
conception, pregnancy and <strong>the</strong> child’s diagnosis – all things that can go
back many years. The studies in which an association was found between
pesticides and cancer seem to be those in which more detailed
information had been received about <strong>the</strong> exposure with respect to timing,
intensity or type of pesticide. Although several studies hint at an
association between pesticide exposure and certain types of cancer, <strong>the</strong>re
does not seem to be sufficient epidemiological evidence of an etiological
relationship between exposure to pesticides and cancer in children
(Daniels et al. 1997; Zahm, Ward 1998).
Studies of <strong>the</strong> risk of cancer in connection with <strong>the</strong> use of pesticides are
often complicated by <strong>the</strong> fact that <strong>the</strong> individual farmer uses many
different kinds of spray products and that <strong>the</strong> individual pesticides have
different toxicological profiles. Many studies have raised a suspicion of
pesticide exposure as <strong>the</strong> possible cause of increased frequency of certain
form of cancer in <strong>the</strong> blood and lymphatic tissue (Zahm et al.1997).
Genotoxic damage, as seen in non-Hodgkin’s lymphoma patients, has
also been found in lymphocytes <strong>from</strong> peripheral blood in persons
exposed to pesticides (Garry et al. 1996). In this connection, it must be
mentioned that farm workers have been exposed many times. Such
repeated exposure may also affect <strong>the</strong> individual farmer’s immune
system (Blair, Zahm 1995).
In Denmark <strong>the</strong>re have not been any real epidemiological studies
concerning pesticide exposure of farm workers, but several researchers
have studied pesticide exposure in horticultural workers. There have
been a few studies of “mortality and occupation”.
An analysis of cancer cases related to occupation in <strong>the</strong> years 1970-79
showed an over-frequency in agriculture of some forms of cancer in <strong>the</strong>
blood and lymphatic tissue. In <strong>the</strong> case of men employed in agriculture,
22 cases of acute leukaemia were found, against an expected 12 cases. In
addition, a significantly increased risk of chronic leukaemia was found
among men in agriculture, with 32 cases of non-acute leukaemia against
an expected 19.2 cases. In this study, <strong>the</strong>re were considerably fewer cases
of lung cancer among agricultural workers than expected (Olsen, Jensen
1987). There is no follow-up on this study <strong>from</strong> <strong>the</strong> period after 1979.
6.1.5 O<strong>the</strong>r effects
Studies in this section have been discussed by Skadhauge (1998).
However, <strong>the</strong> best-documented studies of pesticides were carried out
with substances that are no longer used or that have never been used in
Denmark.
It has been documented that occupational exposure to pesticides can have
a negative effect on fertility (Smith et al. 1997; Strohmer et al. 1993; de
Cock et al. 1994). A known example is <strong>the</strong> substance dibromidechloropropane
(DBCP), which caused azoospermia and oligospermia
among Californian workers working with <strong>the</strong> substance (Whorton, Foliart