Dichloro-Diphenyl-Trichloroethane (DDT)

At a Glance

Dichloro-diphenyl-trichloroethane (DDT) is a pesticide that was first used in World War II in order to control insects that carry human diseases such as malaria. It is also effective against insects such as the gypsy moth, which attack crops. Throughout the 1950s and 1960s, DDT was used increasingly in agriculture. The grave effects of DDT on animal reproduction and wildlife led to its ban in most, but not all, countries. Unfortunately, DDT does not degrade quickly, and it is still present in soil, plants and animal fats all over the world. As a result of consumption of and exposure to these sources, it can be found in blood samples of a majority of people.

What are DDT and DDE?

DDT breaks down into several metabolites (breakdown products). The most common of these is DDE.[1] Though the pesticide is not currently used widely, it persists in human and animal tissues and soil for long periods of time. As a result, it is an ongoing concern for humans. DDT and DDE have long half-lives of about 10 and five years respectively. It is possible that the complete degradation of all existing DDT and DDE could take over 100 years.[2],[3]

Where are DDT and DDE found?

DDT was historically used as an insecticide on crops. It was banned from use in the United States in 1972. It is, however, still used to kill mosquitos in malaria-prone areas such as some sub-Saharan African countries as well as India and North Korea.[4]

In countries where DDT is banned, it is found chiefly in agricultural sites.[5] In these agricultural communities, legacy DDT can be found in low concentrations in the air and drinking water.[6],[7] All other communities are primarily exposed to DDT and DDE through food. It is commonly found in foods that contain animal fats, such as meats and fish, because DDT is a fat-loving molecule that bioaccumulates in the food chain.[8]

What evidence links DDT and DDE to breast cancer?

DDT and DDE disrupt the function of the body’s own hormones, mimicking the actions of estrogens and androgens respectively.[9]

Two studies in people found that early life exposure to DDT increases the risk of breast cancer later in life. Active hormone-mimics such as DDT and DDE are most dangerous during periods of mammary gland development, mainly during pregnancy and puberty.[10],[11],[12]

  • Fetal exposures to DDT and DDE in utero have been linked to an increased risk for breast cancer later in life. In one case, pregnant mothers with high levels of DDT or DDE in their blood were studied. The study found that their daughters were four times as likely to have developed breast cancer 54 years later.[13]
  • Another study was conducted on women who were exposed to DDT throughout its use, beginning in 1945. Participants who were exposed to high levels of DDT prior to the age of 14 were five times as likely to experience breast cancer as women who were not exposed, or first became exposed after the age of 14.[14]

Other studies that examined adult exposures to DDT have been inconclusive,[15],[16],[17] but these studies have looked at blood or urine levels of the chemical at the time of diagnosis of breast cancer, not earlier in life. As indicated above, what may matter most is high levels of DDT exposure during childhood through early adolescence.

In rodents, the disruptive capabilities of DDT are well observed. Rats that were fed DDT were much more likely to develop mammary gland tumors than rats that did not consume DDT.[18]

A 2012 cell-based study suggests that DDT and DDE could promote the formation of tumors in breast cells by disrupting communication between cells.[19]

Who is most likely to be exposed to DDT?

Virtually everyone is exposed to residual DDT and DDE, which remains in soil, plants and the food chain.[20]

Who is most vulnerable to the health effects of DDT and DDE?

DDT exposures seem to have the most profound consequences when they occur during critical periods of breast development, including prenatal development, childhood, puberty and pregnancy.[21],[22]

DDT and DDE cross the placenta, and prenatal exposure appears to increase risk of breast cancer in adulthood.[23] Some of the highest concentrations of DDT and DDE in humans have been found in breast milk, which also makes breast-feeding infants at risk of DDT and DDE exposure.[24],[25] In general, however, the benefits of breast-feeding still outweigh the risks.

Agricultural workers are also at an increased risk of being exposed to DDT. This is because DDT often exists residually in soil as a result its wide use throughout the 1950s and ’60s.[26]

What are the top tips to avoid exposure?

  • Wild fish often have high levels of pesticides, including DDT. Commercial fish that could contain dangerous levels of DDT include Atlantic salmon, American eel, wild striped bass and bluefish.[27]
  • Limiting the consumption of animal fat can also reduce the risk of excessive exposure to DDT and DDE, as it is stored in fat.[28]

[1] Parada, H., Wolff, M., Engel, L., White, A., Eng, S., Cleveland, R., Khankari, N., Teitelbaum, S., Neugut, A., & Gammon, M. (2016). Organochlorine insecticides DDT and chlordane in relation to survival following breast cancer. International Journal of Cancer, 138, 565-575.

[2] Ingber, S., Buser, M., Pohl, H., Abadin, H., Murray, E., & Scinicariello, F., (2013). DDT/DDE and breast cancer: A meta-analysis. Regulatory Toxicology and Pharmacology, 67, 421-433.

[3] DDT (General Fact Sheet). (1999) National Pesticide Information Center. http://npic.orst.edu/factsheets/ddtgen.pdf Retrieved June 2, 2016.

[4] Cone, M. (2009) Should DDT be used to combat Malaria? Scientific American. http://www.scientificamerican.com/article/ddt-use-to-combat-malaria/ Retrieved June 13, 2016.

[5] White, A., Teitelbaum, S., Wolff, M., Stellman, S., Neugut, A., & Gammon, M. (2013). Exposure to fogger trucks and breast cancer incidence in the Long Island Breast Cancer Study Project: a case-control study. Environmental Health 12:24.

[6] Primer: Legacy Pollutants. (2009). Frontline. WGBH Educational Foundation. http://www.pbs.org/wgbh/pages/frontline/poisonedwaters/themes/legacy.html Retrieved June 13, 2016.

[7] World Health Organization (2004). DDT and Its Derivatives in Drinking Water. http://www.who.int/water_sanitation_health/dwq/chemicals/ddt.pdf Retrieved June 6, 2016.

[8] World Health Organization (2004). DDT and Its Derivatives in Drinking Water. http://www.who.int/water_sanitation_health/dwq/chemicals/ddt.pdf Retrieved June 6, 2016.

[9] Pestana D, Teixeira D, Faria A, Domingues V, Monteiro R, Calhau C. Effects of environmental organochlorine pesticides on human breast cancer: putative involvement on invasive cell ability. Environmental toxicology. 2015 Feb 1;30(2):168-76.

[10] Cohn, B., La Merrill, M., Krigbaum,G., Yeh, G., Park, J., Zimmermann, L., & Cirillo, P. (2015). DDT Exposure in utero and breast cancer. Journal of Clinical Endocrinology & Metabolism 100(8) 2865-2872.

[11] Cohn BA, Wolff MS, Cirillo PM, Sholtz RI. DDT and breast cancer in young women: new data on the significance of age at exposure. Environmental Health Perspectives. 2007 Oct 1:1406-14.

[12] Soto AM, Sonnenschein C. Endocrine disruptors: DDT, endocrine disruption and breast cancer. Nature Reviews Endocrinology. 2015 Aug 4.

[13] Cohn, B., La Merrill, M., Krigbaum,G., Yeh, G., Park, J., Zimmermann, L., & Cirillo, P. (2015). DDT Exposure in utero and breast cancer. Journal of Clinical Endocrinology & Metabolism 100(8) 2865-2872.

[14] Cohn BA, Wolff MS, Cirillo PM, Sholtz RI. DDT and breast cancer in young women: new data on the significance of age at exposure. Environmental Health Perspectives. 2007 Oct 1:1406-14.

[15] Ingber, S., Buser, M., Pohl, H., Abadin, H., Murray, E., & Scinicariello, F., (2013). DDT/DDE and breast cancer: A meta-analysis. Regulatory Toxicology and Pharmacology, 67, 421-433.

[16] White, A., Teitelbaum, S., Wolff, M., Stellman, S., Neugut, A., & Gammon, M. (2013) Exposure to fogger trucks and breast cancer incidence in the Long Island Breast Cancer Study Project: a case-control study. Environmental Health 12:24.

[17] Park, J., Cha, E., Ko, Y., Hwang, M., Hong, J., & Lee, W. (2014). Exposure to Dichlorodiphenyltrichloroethane and the risk of breast cancer: A systematic review and meta-analysis. Osong Public Health and Research Perspectives, 5(2), 77-84.

[18] Scribner, J. & Mottet, K. (1981). DDT acceleration of mammary gland tumors induced in the male Sprague-Dawley rat by 2-acetamidophenanthrene. Carcinogenesis, 2(12) 1235-1239.

[19] Pestana D, Teixeira D, Faria A, Domingues V, Monteiro R, Calhau C. Effects of environmental organochlorine pesticides on human breast cancer: putative involvement on invasive cell ability. Environmental toxicology. 2015 Feb 1;30(2):168-76.

[20] Tang M, Zhao M, Shanshan Z, Chen K, Zhang C, Liu W. Assessing the underlying breast cancer risk of Chinese females contributed by dietary intake of residual DDT from agricultural soils. Environment international. 2014 Dec 31;73:208-15.

[21] Soto AM, Sonnenschein C. Endocrine disruptors: DDT, endocrine disruption and breast cancer. Nature Reviews Endocrinology. 2015 Aug 4.

[22] Cohn, B., La Merrill, M., Krigbaum,G., Yeh, G., Park, J., Zimmermann, L., & Cirillo, P. (2015). DDT Exposure in utero and breast cancer. Journal of Clinical Endocrinology & Metabolism, 100(8) 2865-2872.

[23] Park, J., Cha, E., Ko, Y., Hwang, M., Hong, J., & Lee, W. (2014). Exposure to Dichlorodiphenyltrichloroethane and the risk of breast cancer: A systematic review and meta-analysis. Osong Public Health and Research Perspectives, 5(2), 77-84.

[24] DDT (General Fact Sheet). (1999) National Pesticide Information Center. http://npic.orst.edu/factsheets/ddtgen.pdf Retrieved June 2, 2016.

[25] Cohn, B., La Merrill, M., Krigbaum,G., Yeh, G., Park, J., Zimmermann, L., & Cirillo, P. (2015). DDT Exposure in utero and breast cancer. Journal of Clinical Endocrinology & Metabolism, 100(8) 2865-2872.

[26] Tang, M., Zhao, M., Zhou, S., Chen, K., Zhang, C., & Liu, W. (2014). Assessing the underlying breast cancer risk of Chinese females contributed by dietary intake of residual DDT from agricultural soils. Environmental International, 73, 208-2015.

[27] Reducing Your Exposure to DDT and PCBs. (2006) Pollution in People. http://pollutioninpeople.org/results/report/chapter-6/ddt_pcb_5 Retrieved June 7, 2016.

[28] Reducing Your Exposure to DDT and PCBs. (2006) Pollution in People. http://pollutioninpeople.org/results/report/chapter-6/ddt_pcb_5 Retrieved June 7, 2016.

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