Entry into the aquatic environment
Fenitrothion is a contact-acting organophosphorus
pesticide which inhibits acetylcholinesterase (AChE)
activity, thus disrupting the nervous system. In
view of its broad-spectrum action, it is widely
used against insect pests. Most fenitrothion applied
in Europe is used in agriculture, but is also used
in conjunction with pyrethroids to protect stored
grain against insect damage, and in a number of
domestic ant and fly killers.
Most input of fenitrothion into estuarine and marine
waters is likely to be associated with river outflows.
Recorded levels in the marine
Hedgecott (1996) reported limited information on
the concentration of fenitrothion in marine waters.
In a survey of 80 UK rivers and estuaries conducted
in the winter of 1988-89, fenitrothion was below
the detection limit of 10 ng l-1
in all samples (SAC Scientific 1989).
The few data reported for aquatic (freshwater)
sediments indicate low levels of adsorbed fenitrothion.
Monitoring data from the National Rivers Authority
and the National Monitoring Programme Survey of
the Quality of UK Coastal Waters are presented in
Appendix D. No water column concentration was found
to exceed the EQS value (see Appendix D). Monitoring
data were not available for sediments or biota.
The available data suggest that concentrations
of fenitrothion in UK coastal and estuarine water
do not exceed relevant quality standards derived
for the protection of saltwater life.
Fate and behaviour in the marine
Hedgecott (1996) reviewed the fate and behaviour
of fenitrothion. It is not particularly soluble,
and combined with a log octanol-water partition
coefficient (Kow) of 3.38, suggests a moderate tendency
to associate with solids and organic matter. The
low vapour pressure indicates a low tendency to
Fenitrothion is readily degraded by micro-organisms
found in sludge, soil and water via dealkylation,
hydrolysis, oxidation and reduction. The main abiotic
removal process acting on dissolved fenitrothion
is photolysis, with carboxy fenitrothion as the
main product. Weinberger et al (1982b) noted
that fenitrothion dissolved in either fresh or estuarine
water was reduced by 80% (from 2.5 to 0.5 mg l-1)
within six hours when exposed to natural sunlight
in static laboratory systems. Degradation was more
efficient in the estuarine water. In flowing systems,
degradation was slower, possibly as a result of
Caunter and Weinberger (1988) determined a half-life
of about 31 hours for fenitrothion in the light
in the laboratory, with photodegradation apparently
being the major removal process. In the presence
of algae, under similar conditions, the half-life
was only about 16 hours. Sorption to the algae,
and possibly also enhanced photodegradation following
sorption, were responsible for this higher rate
Sorption to aquatic sediments (and soils) is directly
related to their organic content and so varies between
sites. Weinberger et al (1982a) considered
sediments to be a major sink for fenitrothion in
lake microcosms in both the laboratory and the field.
Effects on the marine environment
Toxicity to marine organisms
An exhaustive literature review on the toxicity
of fenitrothion to marine organisms has not been
carried out for the purposes of this profile. The
information provided in this section is taken from
existing review documents (Hedgecott 1996). The
most sensitive groups of organisms have been identified.
Persoone et al (1985) concluded that saltwater
and freshwater crustaceans had similar sensitivities
to fenitrothion, although this conclusion was based
on limited data. Data suggesting similar sensitivities
of fish were somewhat more extensive. There are
too few recent data to assess the validity of these
conclusions. However, Hedgecott (1996) concluded
that data from laboratory studies indicated that
certain species of arthropods were more sensitive
to fenitrothion than any other tested freshwater
For the tiger shrimp Pennies japonicus Kobayashi
et al (1985) obtained 50% survival times
of approximately 24 hours at 1 µg l-1
and 10 hours at 2 µg l-1.
Mayer (1987) reported an EC50 of 1.5 µg l-1
for mobility of brown shrimps Pennies aztecus.
For molluscs, Mayer (1987) reported a 96 hour EC50
of 450 µg l-1 for shell
deposition in juvenile oysters Crassostrea virginica.
Takimoto et al (1987) estimated 96 hour
LC50s of 2.1 mg l-1 and 2.6 mg l-1
for adult killifish Oryzias latipes and mullet
Mugil cephalus respectively when acclimated
to and exposed in water of 23 ppt salinity. Equivalent
LC50s in freshwater were similar, at 3.5 and 2.6
mg l-1 respectively.
Hedgecott et al (196) observed low to moderate
bioaccumulation in marine organisms.
The data on bioaccumulation of fenitrothion by
marine organisms suggest similar levels as those
in freshwater organisms, with BCFs of 179 and 303
for fish and 139 for the tiger shrimp (Takimoto
et al 1987, Kobayashi et al 1985).
Although the shrimp BCF is higher than the figures
for similar freshwater invertebrates, the difference
is not large. McLeese et al (1979) noted
that uptake rates by soft-shelled clams Mya arenaria
and mussels Mytilus edulis were quite low
and excretion rates quite high. The authors suggested
that water concentrations below 0.01 mg l-1
were unlikely to result in significant contamination
of tissues of these organisms.
Potential effects on interest
features of European marine sites
Potential effects include:
- acute toxicity to invertebrates and fish at
concentrations above the EQS of 0.01 mg l-1
(annual average) and 0.25 mg l-1
(maximum allowable concentration) in the water