By Jaclyn Schiff
Monday, November 12, 2007
A study linking DDT exposure to a higher risk of breast cancer in women renews questions about using the pesticide, banned in the U.S., to battle malaria in sub-Saharan Africa.
(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.
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.