A SYNOPSIS O F THE PESTICIDE PROBLEM
101
systems than in terrestrial ones. This is to be expected since aquatic
animals like molluscs and fish have to pass large amounts of water
through their bodies to obtain oxygen and so are particularly likely to
concentrate pesticides. The pattern of concentration in aquatic systems
depends on two types of factor. The first, which has nothing to do with
food chains, is the extent to which animals take up pesticides from contaminated water. Molluscs and fish can concentrate pesticides when they
occur at very low levels (of the order of 0.005 ppm). The second is the
food chain effect; fresh water organisms may eat contaminated terrestrial
insects which fall into the water as a result of forest spraying etc., and
they may also eat aquatic plants and animals which themselves have
concentrated pesticides in their bodies. It should be noted that most
food chains in an ecosystem are relatively short. They rarely comprise
more than five stages, i.e. plant/herbivore/arthropod predatorlvertebrate insectivore/bird or mammal of prey. The linear concept of food
chains is, of course, a concept of convenience; in reality the chains, whatever their lengths, form a, web. Information about the concentration
of pesticides other than the organochlorine insecticides is fragmentary.
Mulla (1966) reports on the ability of the fish Gambusia uflinis to concentrate the organophosphorus insecticide parathion. Extensive surveys of
mercury residues in Swedish birds show that high level residues were significantlymore frequent in predatorybirds than others (Borg et al., 1966).
3. Other Eflects of Fat Solubility
The extent to which the concentration of pesticides in fat affects the
organism depends on the extent to which fat is mobilized, and that
depends on the activity of the animal in relation to its food uptake. In
particular fat is mobilized in starvation, reproduction and on migration.
When pesticides are stored in fat they appear to have no effects, but
when fat is mobilized they are returned to the blood. The work of
Bernard (1963) has demonstrated that house sparrows which were fed
Residue categories of 10 ppm or more in all groups are shaded black.
B/P
Birds feeding mainly on terrestrial plants
B P I ,
,,
,,
,, terrestrial plants and invertebrates
B/I
,, ,, terrestrial invertebrates
B/C
,,
,, ,, carrion, vertebrates, invertebrates, plants
B/M
,,
,,
,, terrestrial mammals
B / M 3
,,
,, ,, terrestrial mammals and birds
BIB
,,
,,
., terrestrial birds
B/FWP ,,
,, ,, freshwater plants
B/FWF ,.
,,
., freshwat,er fish
B/MI,F ,,
,, ,, marine invertebrates and/or marine fish
MOL Molluscs (freshwater and marine)
FISH Fish (freshwater and marine)
MAMM Mammals (herbivores, insectivores and carnivores combined)
101
systems than in terrestrial ones. This is to be expected since aquatic
animals like molluscs and fish have to pass large amounts of water
through their bodies to obtain oxygen and so are particularly likely to
concentrate pesticides. The pattern of concentration in aquatic systems
depends on two types of factor. The first, which has nothing to do with
food chains, is the extent to which animals take up pesticides from contaminated water. Molluscs and fish can concentrate pesticides when they
occur at very low levels (of the order of 0.005 ppm). The second is the
food chain effect; fresh water organisms may eat contaminated terrestrial
insects which fall into the water as a result of forest spraying etc., and
they may also eat aquatic plants and animals which themselves have
concentrated pesticides in their bodies. It should be noted that most
food chains in an ecosystem are relatively short. They rarely comprise
more than five stages, i.e. plant/herbivore/arthropod predatorlvertebrate insectivore/bird or mammal of prey. The linear concept of food
chains is, of course, a concept of convenience; in reality the chains, whatever their lengths, form a, web. Information about the concentration
of pesticides other than the organochlorine insecticides is fragmentary.
Mulla (1966) reports on the ability of the fish Gambusia uflinis to concentrate the organophosphorus insecticide parathion. Extensive surveys of
mercury residues in Swedish birds show that high level residues were significantlymore frequent in predatorybirds than others (Borg et al., 1966).
3. Other Eflects of Fat Solubility
The extent to which the concentration of pesticides in fat affects the
organism depends on the extent to which fat is mobilized, and that
depends on the activity of the animal in relation to its food uptake. In
particular fat is mobilized in starvation, reproduction and on migration.
When pesticides are stored in fat they appear to have no effects, but
when fat is mobilized they are returned to the blood. The work of
Bernard (1963) has demonstrated that house sparrows which were fed
Residue categories of 10 ppm or more in all groups are shaded black.
B/P
Birds feeding mainly on terrestrial plants
B P I ,
,,
,,
,, terrestrial plants and invertebrates
B/I
,, ,, terrestrial invertebrates
B/C
,,
,, ,, carrion, vertebrates, invertebrates, plants
B/M
,,
,,
,, terrestrial mammals
B / M 3
,,
,, ,, terrestrial mammals and birds
BIB
,,
,,
., terrestrial birds
B/FWP ,,
,, ,, freshwater plants
B/FWF ,.
,,
., freshwat,er fish
B/MI,F ,,
,, ,, marine invertebrates and/or marine fish
MOL Molluscs (freshwater and marine)
FISH Fish (freshwater and marine)
MAMM Mammals (herbivores, insectivores and carnivores combined)