DDT

dichloro-diphenyl-trichloroethane (DDT)

Another well-known environmental culprit is dichloro-diphenyl-trichloroethane (DDT). DDT was synthesized in 1874, but it was not until the year of 1939 that its insecticidal properties were discovered. Industrial production of these compounds were subsequently initiated in 1943, (Rakitsky et al, 2002) and since, DDT has been widely used in agriculture mainly for vector control (Yang et al, 2006). Moreover, governmental agencies in developing countries utilize DDT to control the insects that carry diseases like malaria and typhus. In its powder form, DDT also functions as a topically applied louse-control substance, which is a parasitic-like infestation of the skin leading to pruritis, erythema and severe discomfort (Longnecker et al, 1997). Due to its diversity, effectiveness and ease in application, a large amount of DDT was annually being consumed in the early 1960s; around 400, 000 tons. Fortunately, during this same time it was noticed that damage to wildlife and to human health was a result of DDT (Carson, 1962). Therefore, a number of international restrictions were triggered; this began with the Scandinavian country of Sweden (1970), USA (1972) and lastly, the UK (1986) (NRDC, 2001; Chen et al, 2005). However, this didn’t change anything, as DDT is still being used in many parts of the world.

DDT Metabolite DDE (bis[4-chlorophenyl]-1,1-dichloroethane)

With more studies on this troublesome compound, it was revealed that DDT has the capability to transform into its metabolite, DDE (bis[4-chlorophenyl]-1,1-dichloroethane) by partial breakdown in the environment. DDE is known to be more stable and resistant in contrast to DDT. For example, in an individual that has been exposed to DDT, it takes between 10 and 20 years for DDT to disappear whereas, DDE persists throughout the life span of an individual (Rakitsky et al, 2002). Moreover, individuals can be exposed to DDT and DDE from food or occupational exposures - mainly through inhalation and dermal contact. DDT and DDE can also be transferred from the placenta and breast milk to the fetus and infant, respectively (Smith, 1999). This signifies that DDT and DDE affect people in a chain-like manner. Another property of DDT and DDE is that they are highly soluble in lipids and therefore they easily concentrate in human adipose tissue, in addition to other highly lipophilic substances like breast milk (Yang et al, 2006). These substances are found at much higher concentrations in breast milk, in comparison to blood or serum (Somogyi, 1993).

DDT Current Use

Unfortunately, DDT is being used even today in many developing countries. Developed countries that do not suffer similar malarial and typhus insults, have restricted the use of DDT and as a result they have noticed a difference in the concentration of DDT in fat and breast milk over the years. For example, in Sweden the DDT concentration in breast milk fat was 2.9microg/g in 1972 and 0.3microg/g in 1992 (Chen et al, 2005). Such significant results have shown that DDT restriction can have large benefits. However, political support is needed in addition to a combined global effort, as populations in developing countries still suffer significantly from DDT and DDE exposure. In comparison to developed countries, the concentration of DDT and DDE in breast milk fat has not decreased over the years, but has increased (Heinzow, 1998).

References:

Rakitsky V., Tomatis L., and Turusov V. 2002. Dichlorodiphenyltrichloroethane (DDT): Ubiquity, Persistence, and Risks. Environl Health Perspect. 110:125-128.

Yang M, Park MS, and Lee HS. 2006. Endocrine Disrupting Chemicals: Human Exposure and Health Risks. J. Environmental Science and Health Part C. 24: 183-224.

Carson R. 1962. Silent Spring. Boston: Houghton Mifflin Co.

Longnecker., Lucier G., M.P., and Rogan W.J. 1997. The Human Health Effects of DDT (Dichlorodiphenyltrichloroethane) and PCBs (Polychlorinated Biphenyls) and an Overview of Organochlines in Public Health. Annual Reviews of Public Health. 18:21-44.

Natural Resources Defence Council (NRDC). 2001. Healthy Milk, Healthy Baby: Chemical Pollution and Mother’s Milk.
http://www.nrdc.org/breastmilk/chem2.asp - Accessed March 3, 2007.

Chen A., and Rogan WJ. 2005. Health risks and benefits of bis (4-chlorophenyl)-1,1,1-trichloroethane (DDT). The Lancet. 366:763-773.

Smith, D. 1999. Worldwide Trends in DDT Levels in Human Milk. International Journal of Epidemiology. 28:179-188.

Somogyi, A. 1993. Nuturing and Breast-Feeding: Exposure to Chemicals in Breast Milk. Environmental Health Perspectives. 101(Suppl 2):45-52.

Heinzow B., and Schade G. 1998. Organochlorine Pesticides and Polychlorinated Biphenyls in Human Milk of Mothers Living in Northern Germany: Current Extent of Contamination, Time Trend from 1986 to 11997 and Factors that Influence the Levels of Contamination. The Science of the Total Environment. 215:31-39.