Report from the Sub-comittee on the environment and health

Pesticides and cancer
96
<strong>the</strong> so-called re-entry time. During <strong>the</strong> work, <strong>the</strong> amount of pesticides
and <strong>the</strong> area of leaves touched by <strong>the</strong> nurseryman during a working day
are of critical importance. Important factors include <strong>the</strong> length of <strong>the</strong>
working day and <strong>the</strong> substance’s degradation, evaporation and
transferability <strong>from</strong> <strong>the</strong> treated plant surfaces to <strong>the</strong> nurseryman.
There are very few studies of greenhouse workers’ exposure to pesticides
that can be used as models for exposure. Kirknel et al. (1997) mention a
few German and some Dutch studies in this area. The result of <strong>the</strong>
Danish studies accords with those of <strong>the</strong> German and Dutch studies. The
Danish studies must be regarded as representative of a broad section of
work functions in pot-plant nurseries in that <strong>the</strong>y include not only work
directly with plants but also moving of work-benches and packing of
plants. Dutch studies in tall crops in greenhouses, such as tomatoes and
cucumbers, fall within <strong>the</strong> result of <strong>the</strong> Danish model. The result of <strong>the</strong>
Danish model is expressed as <strong>the</strong> 90-percentile, i.e. <strong>the</strong> highest exposure
that 90% of a group of nurserymen can be exposed to. This cut-off point
is generally regarded as high, with good safety. The Danish studies do
not include <strong>the</strong> spraying of pesticides. Most spraying of pesticides in
greenhouses is done automatically, with little risk of exposure. However,
<strong>the</strong>re is some limited spraying in Danish greenhouses with a hand-held
spray gun, where <strong>the</strong> exposure is considered to be relatively high.
Measurements of this work function are being studied in <strong>the</strong> UK
(personal information, Erik Kirknel).
Kirknel et al. (1997) have developed a model for <strong>the</strong> exposure to and
absorption of pesticides on re-entry into greenhouses. The daily potential
exposure can here reach approx. 100 milligrammes of pesticide per
working day, but typically lies in <strong>the</strong> interval 1-60 milligrammes in a
working day of 6 hours with contact with <strong>the</strong> treated plants one day after
<strong>the</strong> pesticide treatment. The most critical variable is <strong>the</strong> rate at which <strong>the</strong>
pesticide disappears <strong>from</strong> <strong>the</strong> plant’s surface. In <strong>the</strong> exposure model,
account is also taken of <strong>the</strong> amount of pesticide that can penetrate <strong>the</strong>
skin. It is only <strong>the</strong> amount that penetrates <strong>the</strong> skin that causes possible
health effects. The amount is normally less than <strong>the</strong> amount that lands on
<strong>the</strong> skin.
6.1.4 Risk of cancer
Human data on exposure to pesticides and cancer are mainly based on
occupational exposure in farming, forestry and horticulture and among
workers employed in <strong>the</strong> production of pesticides. Reviews of <strong>the</strong>se
studies have not revealed a significant rise in <strong>the</strong> total mortality <strong>from</strong>
cancer among persons occupationally exposed to pesticides (Dich et al.
1997; Maroni, Fait 1993; Blair, Zahm 1991). Fur<strong>the</strong>rmore, <strong>the</strong> total
mortality was found to be lower among <strong>the</strong>se groups of persons exposed
to pesticides than among <strong>the</strong> general population. This has usually been
ascribed to a “healthy worker effect” and, in <strong>the</strong> case of people employed
in farming, to a healthier lifestyle among farming families. However,
farmers, in particular, seem to have a higher occurrence of some types of
cancer, including non-Hodgkin’s lymphoma, Hodgkin’s disease, multiple
myeloma, leukaemia, soft-tissue sarcoma and cerebral cancer, skin
cancer, lip cancer, stomach cancer and prostate cancer (Dich et al. 1997;
Blair, Zahm 1995: Blair et al. 1992). Most epidemiological studies of
cancer and pesticides have dealt with pesticides as a whole and are short