DDT leaves behind a legacy of long-lasting contamination and harm to both humans and ecosystems. Banned in the U.S. nearly 40 years ago, DDT and its breadown products were found in the blood of 99% of people recently tested by the CDC. USDA found DDT breakdown products in 60% of heavy cream samples, 42% of kale greens, 28% of carrots and lower percentages of many other foods.
The science on DDT's human health impacts has continued to mount over the years, with recent studies showing harm at very low levels of exposure. Studies show a range of human health effects linked to DDT and its breakdown product, DDE:
- Cancer: Girls exposed to DDT before puberty are 5 times more likely to develop breast cancer in middle age, according to the President’s Cancer Panel. DDT has also been associated with liver and pancreatic cancer. The International Agency for Research on Cancer classifies DDT as "possible carcinogenic to humans."
- Reproductive Effects: DDT is linked to male infertility, impaired semen quality, miscarriages, early menopuase, birth defects, and low birth weight.
- Endocrine Disruption: DDT's estrogenic effects have been known for some time. Studys suggest DDT can interefere with a mother's ability to lactate and elevate risk of testicular cancer.
- Neurological effects: Research suggests that women’s exposure to DDE in early pregnancy is linked with changes in thyroid hormone levels, which in turn affects fetal brain development. Observed effects include reduced motor skills and a decrease in verbal, memory, and quantitative and perceptual performance skills among preschoolers. People exposed to higher levels of DDT experience immediate neurotoxic effects such as tremors and seizures, as well as nausea, vomiting, and dizziness.
[Text Box: Childhood Exposure & Body Burden: Research shows that childhood exposure to DDT begins before birth.
- Pregnant women pass DDT to their unborn baby through the placenta, while nursing infants receive doses of DDT though their mother's breastmilk.
- Children are exposed to higher levels of DDT than adults due to their smaller body size. Studies show infants consume 4 times as much DDT as the average adult.]
DDT's toxic effects on ecosystems are well known. DDT concentrates up the food chain, reaching high levels in fish and marine mammals. DDT can travel long distances in the atmosphere, which is why it is found on almost every corner of the earth and in places where it has never been used. In the Arctic and Antarctic regions, research shows DDT and its breakdown products in the atmosphere, snow, and wildlife.
[Text Box: Environmental Persistence: Despite bans, DDT can persist in the environment for decades:
- Concentrations of DDT near a former manufacturing facility at McIntosh, Alabama still represent a significant risk to fish and piscivorous birds in the area--- even though the plant ceased production over 40 years ago, says a recent study.
- Despite dropping DDT levels in the Arctic's birds, whales, and seals, Adélie penguins in the Antarctic continue to have the same levels of DDT in their bodies as they did 30 years ago. Heidi Geisz of the Virginia Institute of Marine Science and her colleagues found that the birds were being exposed to DDT that was previously locked up in glaciers. See also: Antarctic Melt Releasing DDT, Tainting Penguins]
Experience tells us that eliminating DDT generally improves the health of ecosystems. Since DDT was banned in the U.S., bald eagles have made a dramatic recovery, along with a several other bird species. An Environmental Defense Fund article summarizes:
- Since 1963 the bald eagle population has rebounded, increasing from less than 500 pairs to over 5,000 nationwide.
- Peregrene falcons totaled only 39 breeding pairs in 1975. By 1996 however, their population multiplied to 993 pairs.
- Ospreys have also made a comeback---increasing from less than 8,000 breeding pairs to 14,246 pairs.
Wiping out malaria with DDT is an unrealistic goal. Mosquito resistance among malaria carrying mosquitos forced governments years ago to adopt a more diverse, integrated approach to malaria control.
Long before the United States banned DDT, mosquito populations evolved defenses to DDT's toxins. Mosquitos showed signs of resistance to DDT as early as 1947---only one year after the insecticide was introduced for mosquito control (See: Insecticide Resistance in Insect Vectors of Human Disease). By 1972, nineteen species of mosquitos were resistant to DDT in Africa alone.
[Text Box: Malaria Eradication in the United States:
Once endemic in the United States, malaria decreased rapidly in the first half of the 20th century, without the insecticidal powers of DDT. According to the CDC, from 1920 to 1946, malaria cases decreased from 400 out of 100,000 inhabitants to only 30 cases per 100,000. Malaria deaths likewise decreased from 60 deaths per million to only 2 deaths per million. In 1947 the U.S. commenced the National Malaria Eradication Program which included drainage, removal of mosquito breeding grounds, and some DDT in areas where malaria was still prevelant. ]
Research & Factsheets
- ASTDR Factsheet and full Toxicologica Profile for DDT.
- CDC Chemical Information on DDT
- The Pine River Statement: Human Health Consequences of DDT Use. A comprehensive assessment of the science behind DDT's health effects.
- CDC 4th Report on Human Exposure to Environmental Chemicals
President's Cancel Panel Report Reducing Environmental Cancer Risk: What We Can Do Now.
- DDT and Breast Cancer in Young Women: New Data on the Significance of Age at Exposure.
DDT & other POPs in the blood of pregnant women in South Africa.
- Developmental Effects of Endocrine-Disrupting Chemicals in Wildlife and Humans. Theo Colburn's 1993 article discusses the estrogenic effects of DDT.
- Insecticide Resistance in Insect Vectors of Human Disease
- Global Status of DDT & Its Alternatives for Use in Vector Control to Prevent Disease,
Scientists say: DDT use should be curtailed, left only as 'last resort' in some malaria-plagued areas, Marla Cone, Environmental Health News, May 2009
- Study: Insecticide-treated net coverage in Africa: mapping progress in 20007, The Lancet, January 2009
- Cost and consequences of large scale vector control for Malaria, Malaria Journal, December 2008
- Technology to eradicate malaria, BBC News, November 2008
- War Against Malaria Can Be Won, Without DDT, Dr. César Chelala,The Epoch Times, October 2008
- Rwanda: Lessons learnt from 2007 Spraying Campaign, September 2008
- China's Pearl River tainted with DDT, January 2008
Additional Health Research: Reproductive Harm:
- Exposure of Mother - Child and Postpartum Woman - Infant Pairs to DDT and its Metabolitescience of the Total Environment.
- Impaired Semen Quality Associated With Environmental DDT Exposure in Young Men Living in a Malaria Area in the Limpopo Province.
Addition Health Research: Infants and Breastmilk
- Nonmalarial Infant Deaths and DDT Use for Malaria Conrol Emerging.
- DDE and Shortened Duration of Lactation in a Northern Mexican Town.
- Transfer of DDT used in malaria control to infants via breast milk.
- Polychlorinatedbiphenyls (PCBs) and dichlorodiphenyl dichloroethene (DDE) in human milk: Effects on growth, morbidity, and duration of lactation.