Toxicity of DDT

Organic Pollutants An Ecotoxicological Perspective, Second Edition 

FIGURE 5.4 Sites of action of organochlorine insecticides (a) sodium channel, (b) GABA receptor. (From Eldefrawi and Eldefrawi 1990. With permission.) 

Apart from the action upon Na+ channels, p,p -DDT and its metabolites can have certain other toxic effects. It has been reported that p,p -DDT can inhibit certain ATPases (see EHC 83). In fish, the inhibition of ATPases can affect osmoregulation. 

Finally, there is evidence that constituents of technical DDT can have a feminizing effect on avian embryos (for further discussion, see Chapter 15, Section 15.6). Of 

From an ecotoxicological point of view, it has often been suspected that sublethal effects, such as those described here, can be more important than lethal ones. Both p,p -DDT and p,p -DDD are persistent neurotoxins, and may very well have caused behavioral effects in the field. This issue was not resolved when DDT was widely used, and remains a matter for speculation. More is known, however, about eggshell thinning caused by p,p -DDE and its effects upon reproduction, which will be discussed in Section 5.2.5.I. 

---

The two examples just given are of localized effects associated with the acute toxicity of DDT and DDD to organisms in higher trophic levels. A more wide-ranging toxic effect associated with population decline was eggshell thinning caused by the relatively high levels of p,p -DDE in some predatory birds (see Table 5.7). 

Table XL Comparative Toxicity of DDT and DFDT and Some Miscellaneous Organofluorine Insecticides to Vertebrates...

The human toxicity of DDT has been a subject of intense study during the last 20-25 years. This led the World Health Organisation to prohibit the use of DDT as an insecticide. The long-term use of DDT resulted in the development of resistance to the insecticide in many pests (over 200 species). As a result, most developed countries initiated programmes for the gradual replacement of DDT. The manufacture of DDT, and consequently that of chloral, has been in gradual decline since 1963 [12, 13,17]. 

DDT, discovered by Dr. Mueller in Switzerland, and used for insect vector control during World War II, quickly found a place in forestry, as well as agriculture. The material proved highly effective in the control of such insects as the spruce budworm, tussock moth, hemlock looper, and many others. It was widely used in the Northeast for control of the introduced Gypsy moth during these early years. The low toxicity of DDT to mammals made it to appear to be an excellent insecticide for forestry use. It was only after subsequent studies revealed the impact on other species that reservations about its use was raised. 

The high acute toxicity of DDT analogs and most pyrethroids to fish is one of the most significant hazards associated with the widespread use of these compounds. The high toxicity of pyrethroids to fish appears to result in part from high intrinsic sensitivity of the CNS to these compounds (JJ3,J7) Fish are also highly sensitive to some... 

Although the toxicity of DDT to the amphipod Hyalella azteca decreased with increasing carbon content of the sediment, this was not the case for endrin (Nebeker et al. 1989) so that specific mechanisms of interaction even between neutral xenobiotics and the organic carbon in the sediment phase may be of determinative significance. The results with DDT are, in fact, consistent with evidence from equilibrium dialysis experiments of its association with dissolved humic material (Carter and Suffet 1982). 

Spiller, D. 1963. Insecticide resistance effects of WARF antiresistant on toxicity of DDT to adult houseflies. Science, 142, 585-586. 

Kouyoumjian HH, Villeneuve JP (1979) Further studies on the toxicity of DDT to planaria. Bull Environ Contam Toxicol 22 109-112... 

Zakarya, D., Boulaamail, A., Larfaoui, E. M., and Lakhlifi, T. (1997) QSARs for toxicity of DDT-type analogs using neural network. SAR QSAR Environ. Res. 6,183-203. 

---