The Organochlorine Insecticides - Organic Pollutants: An Ecotoxicological Perspective - page 106

taBLe 5.3
Half-Lives of p,p ′ -ddt and related compounds

material/
organism

material/
organism compound t 50 (years) compound t 50 (days)

Soil 2.8 Feral pigeon

( Columba livia )

28

p,p ′-DDT p,p ′-DDT

p,p ′-DDD Soil 10+

(British soils)

p,p ′-DDD Feral pigeon 24

p,p ′-DDE Feral pigeon 250

p,p ′-DDT Bengalese finch

( Lonchura striata)

10

Hens ( Gallus
domesticus )

36-56 (in fat)

p,p ′-DDT

p,p ′-DDT Rat 57-107

p,p ′-DDT Rhesus monkey 32 and 1520

Source: Data from Edwards (1973) and Moriarty (1975).

Some data on the half-lives of these three compounds are given in Table 5.3. All
of them are highly persistent in soils, with half-lives running to years once they
become adsorbed by soil colloids (especially organic matter—see Chapter 3). The
degree of persistence varies considerably between soils, depending on soil type and
temperature. The longest half-lives have been found in temperate soils with high
levels of organic matter. (See, for example, Cooke and Stringer 1982.) Of particular
significance is the very long half-lives for p,p ′-DDE in terrestrial animals, approach-
ing 1 year in some species, and greatly exceeding the comparable values for the
other two compounds. This appears to be the main reason for the existence of much
higher levels of p,p ′-DDE than of the other two compounds in food chains even when
technical DDT was widely used. Following the wide-ranging bans on the use of DDT
in the 1960s and 1970s, p,p ′-DDT residues have fallen to very low levels in biota,
although significant residues of p,p ′-DDE are still found, for example, in terrestrial
food chains such as earthworms → thrushes → sparrow hawks in Britain (Newton
1986) and in aquatic food chains.
A nationwide investigation of OC residues in bird tissues and bird eggs was con-
ducted in Great Britain in the early 1960s, a period during which DDT was widely
used (Moore and Walker 1964). The most abundant residue was p,p ′-DDE; levels
of p,p ′-DDT and p,p ′-DDD were considerably lower. Levels in depot fat were some
10-30-fold higher than in tissues such as liver or muscle. The magnitude of residues
was related to position in the food chain, with low levels in omnivores and herbivores
and the highest levels in predators at the top of both terrestrial and aquatic food
chains (see Walker et al. 1996, Chapter 4). Similar results were obtained with both
bird tissues and eggs. The highest p,p ′-DDE levels (9-12 ppm) were found in the
eggs of sparrowhawks, which are bird eaters, and in herons ( Ardea cinerea ), which
are fish eaters. Thus, when considering the fate of technical DDT in food chains
generally, p,p ′-DDE was found to be more stable and persistent (i.e., refractory) than