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Endosulfan is an organochlorine pesticide that is used in
agriculture. Adverse effects of endosulfan on humans as well as on
mammals are well documented. Fish, in particular salmonids, seem to
be very sensitive to waterborne endosulfan exposure. Information
regarding the effects of oral exposure to fish is very limited.
Studies on farmed fish are needed in order to give appropriate
safety recommendations for endosulfan in fish feeds The current EU
maximum level (ML) for endosulfan in fish feed is considerably
lower than in feed for terrestrial farm animals (5 vs. 100
microgram per kilo feed), possibly limiting the choice of plant
products by the feed industry.
Feeding experiment with endosulfan
In an initial range finding study, Atlantic salmon pre-smolt
(weighing about 50 gram) received diets that contained increasing
concentrations of endosulfan (4, 50 or 710 microgram endosulfan per
kilo feed) or a control diet for 49 days. General, haematology and
clinical chemistry in plasma as well as tissue histology and
biochemistry were used to detect adverse effects on fish
health.
Results
The feed concentrations of endosulfan did not result in clear
clinical symptoms or clear adverse effects on the plasma and blood
parameters. Only minor and transient responses were noted in the
highest dose group. Certain haematological parameters (Hemoglobin,
Hematocrit) were significantly increased in the highest exposure
group on day 35, but had returned to levels similar to controls by
day 49. Elevated concentrations of a liver enzyme (ASAT) were
detected in two fish in the highest dose group, but there was no
significant difference among treatments. Similarly, the proportion
of different white blood cells (leucogram) was not affected by
treatment, while lymphocytes of two fish in the highest group
showed irregularities in the cell nuclei. The liver showed an
increased detoxification (as EROD activity) and intestinal
Na+, K+-ATPase activity was inhibited in the
highest exposure group (710 μg kg-1), Other hepatic
indicators of stress impacts and responses remained unchanged. In
contrast to the biochemical results, hepatic and intestinal
histology revealed changes of exposure even at the lowest dose
tested.
How much endosulfan is tolerated?
No acute toxicity occurs when salmon is exposed to feeds levels
up to 710 μg kg-1. The organismal relevance of the
histological changes must be considered in the absence of effects
in other biomarkers at exposure levels under 710 μg
kg-1. Ongoing research is investigating the impact of
dietary endosulfan exposure over longer, chronic, exposure
periods.
Contact person: Marc Berntssen at the Seafood Safety
Research Program, NIFES.
E-mail: marc.berntssen@nifes.no
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Welcome to NIFES` stand, D340, at the NorFishing exhibiton
in Trondheim, Norway, to collect scientific results.
The article presented on this page represent just some of
the scientific results you may collect at NIFES` stand, D340, at
the AquaNor exhibition in Trondheim, Norway, 14th-17th of August,
2007. Please feel free to visit us at our stand.
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