It was banned from use in the United States in 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.
In countries where DDT is banned, it is found chiefly in agricultural sites. These chemicals are commonly found in foods that contain animal fats where DDT accumulates, such as meats and fish. The most important and comprehensive set of studies linking subsequent development of breast cancer and exposures to DDT, especially during early development and pregnancy, come from the Child Health and Development Study CHDS.
The CHDS is a large, long-term study that originally enrolled women in Alameda County, California between and , very early during their pregnancies. In the first few days after the women gave birth, blood samples were taken from the mothers and stored. Over the past 60 years or so, scientists have followed the health of both the mothers from this study as well as their daughters who are now approaching, on average, their mid-fifties.
Several papers have reported important findings from the CHDS. Results of many other recent studies, from both the U. In a report from Iran, higher blood levels of DDT and DDE were each associated with increases in both benign and malignant breast cancer, as compared to women with low blood levels of these chemicals. One study from Taiwan did look at age at exposure, although the data were gathered at the township level, i.
Results indicated that DDT exposure before the age of five years old was associated with an increased risk of cancer, and the results were strengthened as the number of DDT exposures increased. Other studies that examined adult exposures to DDT have been inconclusive, [24] , [25] , [26] 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. The chemical does not easily break down and is known by scientists to accumulate in the tissues of animals. Last year, the Los Angeles Times revealed that decades ago DDT manufacturers sunk leaking barrels contaminated with DDT deep into the Pacific Ocean off the coast of California—possibly as many as half a million barrels.
The contamination of fish and other sea life has persisted over decades, and a recent study linked DDT and other pollutants to aggressive cancer seen in California sea lions. Bruce Blumberg, professor of cell and developmental biology at the University of California, Irvine, said the story of DDT underscores the failure of companies and regulators to protect public health from the dangers of many chemicals.
The government needs to fund studies that extend over multiple generations and truly examine the impacts of chemicals such as DDT on human health, he said. Once you let that genie out of the bottle, it keeps on giving. Something went wrong. Please email webmaster sierraclub. By signing up, you are opting in to receive periodic communications from the Sierra Club. Carey Gillam is a journalist and author , and a public interest researcher for US Right to Know , a not-for-profit food industry research group.
You can follow her on Twitter careygillam. Report shows a critical need to study other pesticides and chemicals. By Carey Gillam Apr 23 Disrupting hormones DDT dichloro-diphenyl-trichloroethane was introduced in the s as a highly effective insecticide designed to combat the spread of malaria, typhus, and other diseases carried by insects. Like what you read? Since then, studies have continued, and a relationship between DDT exposure and reproductive effects in humans is suspected, based on studies in animals.
In addition, some animals exposed to DDT in studies developed liver tumors. As a result, today, DDT is classified as a probable human carcinogen by U. After the use of DDT was discontinued in the United States, its concentration in the environment and animals has decreased, but because of its persistence, residues of concern from historical use still remain.
Since , EPA has been participating in international negotiations to control the use of DDT and other persistent organic pollutants used around the world. Under the auspices of the United Nations Environment Programme, countries joined together and negotiated a treaty to enact global bans or restrictions on persistent organic pollutants POPs , a group that includes DDT. The Convention includes a limited exemption for the use of DDT to control mosquitoes that transmit the microbe that causes malaria - a disease that still kills millions of people worldwide.
In September , the World Health Organization WHO declared its support for the indoor use of DDT in African countries where malaria remains a major health problem, citing that benefits of the pesticide outweigh the health and environmental risks. It is up to individual countries to decide whether or not to use DDT. EPA works with other agencies and countries to advise them on how DDT programs are developed and monitored, with the goal that DDT be used only within the context of programs referred to as Integrated Vector Management.
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