Toxicological Effects of DDT

  • Acute toxicity: DDT is moderately to slightly toxic in studied mammalian species taken orally.
  • Chronic toxicity: DDT has caused chronic effects on the nervous system, liver, kidneys and immune system in experimental animals.
  • Reproductive effects: There is evidence that DDT causes negative reproductive effects in test animals and humans. (Pubmed Dec 2006, Aneck-Harn, Schulenburg, Bornman, De Jager)
  • Teratogenic effects: There is evidence that DDT causes teratogenic effects in test animals as well.
  • Mutagenic effects: The evidence for mutagenicity and genotoxicity is contradictory. However, in humans, blood cell cultures of men occupationally exposed to DDT showed an increase in chromosomal damage.
  • Carcinogenic effects: The evidence regarding the carcinogenicity of DDT is equivocal.
  • Organ toxicity: Acute human exposure data and animal studies reveal that DDT can affect the nervous system, liver and kidney.
  • Fat in humans and animals: DDT is very slowly transformed in animal systems.

Ecological Effects of DDT

  • Effects on birds: DDT may be slightly toxic to almost non-toxic in birds.
  • Effects on aquatic species: DDT is very highly toxic in many aquatic invertebrate species.
  • Effects on other animals (non-target species): Earthworms are not susceptible to acute effects of DDT and its metabolites at levels higher than those likely to be found in the environment, but they may serve as an exposure source to species that feed on them.

Environmental Effects of DDT

  • Breakdown in soil and groundwater: DDT is very highly persistent in the environment, with a reported half-life of between 2-15 years and is immobile in most soils. Routes of loss and degradation include: runoff, volatilisation, photolysis and biodegradation (aerobic and anaerobic).
  • Breakdown of chemical in surface water: DDT may reach surface waters primarily by runoff, atmospheric transport, drift, or by direct application (e.g. to control mosquito-borne malaria). The reported half-life for DDT in the water environment is 56 days (in lake water) and approximately 28 days in river water.
  • The main pathways for loss are volatilization, photo-degradation, adsorption to water-borne particulates and sedimentation. Aquatic organisms, as noted above, also readily take up and store DDT and its metabolites.
  • Breakdown of the chemical in vegetation: DDT does not appear to be taken up or stored by plants to a great extent. It was not seen to be translocated into alfalfa or soybean plants, and only trace amounts of DDT or its metabolites were observed in carrots, radishes and turnips all grown in DDT-treated soils. Some accumulation was reported in grain, maize and rice plants, but little translocation occurred and residues were located primarily in the roots.

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