98
N. W. MOORE
outside the area of application. Pesticides may be carried as vapour
and as dusts by wind currents, and in solution or suspension in water.
Persistence also allows time for substances to be ingested by one animal
and passed to another. The extent to which this occurs depends on the
power of the organism to metabolize the pesticide. If it is able to excrete
the pesticide quickly or to break it down to harmless metabolites which
remain within the body, there will be no possibility of a harmful food
chain effect. On the other hand, if the pesticide is not excreted quickly,
and particularly if it is stored in the fat, concentration in food chains
is inevitable (see p. 99). Of the pesticides used today only the persistent
organochlorine insecticides combine the characteristics of persistence
and fat solubility. As a result these substances become widely dispersed
and concentrated in food chains. From many points of view they pose
special problems; ecologically they are the most interesting group of
pesticides.
1. Dispersal
I n recent years gas-liquid chromatography techniques have been so
refined that very small quantities of organochlorine insecticides can
now be detected in living and non-living material. These substances
have been detected in air (Turner, 1965), rain water (Wheatley and
Hardman, 1965), fresh water (e.g. Cope, 1966), salt water (e.g. Butler,
1966), soils (e.g. Wheatley et al., 1962),'muds (e.g. J. 0. Keith, 1966),
plants (e.g. J. 0. Keith, 1966), invertebrates, fish, birds and mammals.
Nearly all the birds analysed in a survey in Britain from 1962-65 contained organochlorine insecticide residues. They came from 37 counties
and all major habitats. A high proportion contained both DDT and/or
its metabolites and dieldrin (Moore and Walker, 1964, and Moore, 1965a).
The finding of organochlorine insecticide residues mostly within the
range 0.4-3.4 ppm in all 90 eggs of 13 species of seabirds from English,
Scottish and Irish colonies, suggests that environmental contamination
by these substances is universal in the British Isles (Moore and Tatton,
1965). Organochlorine insecticide residues have been found in even more
remote districts, for example in plants in the Northwest Territories of
Canada (Sheldon et al., 1964) and in fish, penguins, skuas and seals in
the Antarctic (George and Frear, 1966).
The presence of organochlorine insecticides in aquatic animals is at
first sight surprising considering that organochlorine insecticides have
exceptionally low solubility in water. J. 0. Keith (1966) has shown that
these substances occur a t much higher levels in suspended material than
in the filtrate. Their dispersal is likely t.0 be through adsorption onto organic particles. Both natural and man-made surface oil filins are likely
to be important as carriers of orgnnochlorine insecticides. The immense
N. W. MOORE
outside the area of application. Pesticides may be carried as vapour
and as dusts by wind currents, and in solution or suspension in water.
Persistence also allows time for substances to be ingested by one animal
and passed to another. The extent to which this occurs depends on the
power of the organism to metabolize the pesticide. If it is able to excrete
the pesticide quickly or to break it down to harmless metabolites which
remain within the body, there will be no possibility of a harmful food
chain effect. On the other hand, if the pesticide is not excreted quickly,
and particularly if it is stored in the fat, concentration in food chains
is inevitable (see p. 99). Of the pesticides used today only the persistent
organochlorine insecticides combine the characteristics of persistence
and fat solubility. As a result these substances become widely dispersed
and concentrated in food chains. From many points of view they pose
special problems; ecologically they are the most interesting group of
pesticides.
1. Dispersal
I n recent years gas-liquid chromatography techniques have been so
refined that very small quantities of organochlorine insecticides can
now be detected in living and non-living material. These substances
have been detected in air (Turner, 1965), rain water (Wheatley and
Hardman, 1965), fresh water (e.g. Cope, 1966), salt water (e.g. Butler,
1966), soils (e.g. Wheatley et al., 1962),'muds (e.g. J. 0. Keith, 1966),
plants (e.g. J. 0. Keith, 1966), invertebrates, fish, birds and mammals.
Nearly all the birds analysed in a survey in Britain from 1962-65 contained organochlorine insecticide residues. They came from 37 counties
and all major habitats. A high proportion contained both DDT and/or
its metabolites and dieldrin (Moore and Walker, 1964, and Moore, 1965a).
The finding of organochlorine insecticide residues mostly within the
range 0.4-3.4 ppm in all 90 eggs of 13 species of seabirds from English,
Scottish and Irish colonies, suggests that environmental contamination
by these substances is universal in the British Isles (Moore and Tatton,
1965). Organochlorine insecticide residues have been found in even more
remote districts, for example in plants in the Northwest Territories of
Canada (Sheldon et al., 1964) and in fish, penguins, skuas and seals in
the Antarctic (George and Frear, 1966).
The presence of organochlorine insecticides in aquatic animals is at
first sight surprising considering that organochlorine insecticides have
exceptionally low solubility in water. J. 0. Keith (1966) has shown that
these substances occur a t much higher levels in suspended material than
in the filtrate. Their dispersal is likely t.0 be through adsorption onto organic particles. Both natural and man-made surface oil filins are likely
to be important as carriers of orgnnochlorine insecticides. The immense