(WOMENSENEWS)–Every year, young children and pregnant women in sub-Saharan Africa are the majority of the roughly 500 million people who contract malaria and the more than 1 million people who die of the disease each year, World Health Organization data show.
In response, the WHO in September 2006 reversed years of malaria control policy when it joined a solid consensus among malaria experts and began recommending the use of the pesticide DDT, or dichlorodiphenyltrichloroethane, in areas with high rates of malaria transmission.
Barbara A. Cohn, an epidemiologist and director of University of California-Berkeley’s Child Health and Development Studies program, however, cautions that the health risks of exposure to DDT–banned as an agricultural pesticide in the United States in 1972 for posing unacceptable risks to humans and the environment–should nonetheless remain on the public health radar.
"There is enough evidence to suggest that DDT does not represent a zero risk to human health," said Cohn. "I would never advocate not considering the use of DDT for malaria, but I do advocate balance."
Cohn co-authored a study linking childhood exposure to DDT among a group of U.S. women to higher rates of breast cancer. The study was published in the October issue of Environmental Health Perspectives, a journal about the impact of the environment on human health based in Raleigh, N.C.
She notes that in addition to breast cancer DDT exposure has been associated with premature births, shortened lactation and impaired neurological function in infants who were exposed to the chemical in the womb.
Childhood Exposure Increases Risk
In Cohn’s study, women who were exposed to DDT as children were five times more likely to develop breast cancer than women who were exposed when they were older.
Cohn worked with colleagues to measure the amount of DDT in blood samples collected from 129 women in and around Oakland, Calif., between 1959 and 1967. The archived samples coincide with the time period during which the use of DDT peaked in the United States.
While a number of studies since the early 1990s found evidence linking DDT exposure to breast cancer, this is the first to measure how childhood exposure affects a woman’s risk of breast cancer.
Cohn said that she and the other researchers decided to look at the age variable in part because evidence from a 2003 study on animals show that the "mammary gland is vulnerable to certain insults largely at a young age."
Steven Milloy, a biostatistician who runs the Web site Junkscience.com, minimized the policy significance of the study in an exchange with Cohn and her co-authors in letters to the editor of the Wall Street Journal. In an interview, Milloy said, "Assuming purely for the sake of argument that DDT does increase the risk of breast cancer" it would still make sense to use it for malaria control because malaria is such a big health threat. He pointed to Zimbabwe’s 2,000 cases of breast cancer a year, affecting 0.016 percent of the population, while about 12 percent of the population, or 1.5 million people, are infected with malaria annually.
The WHO’s 2006 recommendation has led the way for a number of other organizations involved with the funding and execution of malaria control activities–including the President’s Malaria Initiative and the Global Fund to Fight AIDS, Tuberculosis and Malaria–to incorporate DDT into their projects.
Regular Reviews of DDT Policy
The WHO characterizes DDT as a chemical with "low acute toxicity" but the organization re-evaluates the risk that DDT poses to human health as new research emerges.
In its October 2007 DDT position statement, WHO said "new information published since 2000 is being evaluated . . . Based on the most recent information, WHO has no reason to change its current recommendations on the safety of DDT."
Richard Tren, director of Africa Fighting Malaria, a nonprofit health advocacy group based in South Africa and Washington, stresses that Cohn’s study analyzes how women respond to the use of DDT in agriculture, "not the targeted use of DDT in malaria control," which is sprayed in amounts of two grams per square meters.
Tren says studies like Cohn’s about human health effects of chemicals are of universal interest because human bodies tend to react pretty much the same way around the world. However, he says, people in Africa face a unique risk in malaria. "No one in the U.S. faces any real risk from malaria or other insect-borne diseases. That is not true in Africa where these diseases are ever present and rob millions of their lives every year."
DDT is just one of 12 pesticides that WHO currently recommends for malaria control.
Chemical’s Low-Cost Benefits
One advantage of DDT is that it lasts almost twice as long as the other chemicals, which means it cuts costs by requiring fewer applications.
"The negative health effects of DDT would have to be overwhelming in order to be more significant than the beneficial effects on malaria," said Henry I. Miller, research fellow at the Hoover Institution in Stanford, Calif. Miller said malaria affects vast numbers of people and the ability of entire nations and regions to succeed.
The U.S. branch of the World Wildlife Fund, based in Washington, D.C., said it supports the continued use of DDT for malaria control until viable alternatives are available. "We would eventually like to see it phased out," a spokesperson said. Greenpeace takes a similar position.
Sonia Shah, an investigative journalist who is writing a book about the history and politics of malaria, says that instead of using DDT, malaria could be fought by minimizing contact with malarial mosquitoes through such measures as installing screens in houses, eliminating standing water from roads, increasing jobs that allow people to remain indoors and creating better access to clean water.
"The reason why DDT is considered so effective and rapid is because it doesn’t require any of these time-consuming, expensive things," Shah wrote in an e-mail. "It is cheap and very little infrastructure is required to use it. It may help relieve malaria in some places, at some times. But unlike DDT, safe housing, jobs, clean water, clinics and schools will not contaminate local ecosystems . . . And we’d get a lot more than just an end to malaria."
At the end of the day, Cohn observes that after potential benefits and risks are considered, the decision to use DDT or not has more to do with politics and culture than pure science.
Jaclyn Schiff is a staff writer for GlobalHealthReporting.org and freelance journalist based in Washington, D.C. She can be reached at [email protected].
For more information:
Environmental Health Perspectives, "DDT and Breast Cancer in Young Women: New Data on the Significance of Age at Exposure":
http://www.ehponline.org/members/2007/10260/10260.html
World Health Organization Malaria Page:
http://www.who.int/topics/malaria/en/
Stockholm Convention on Persistent Organic Pollutants:
http://www.pops.int/
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