(Beyond Pesticides, May 30, 2008)

A recent study has linked the common herbicide atrazine with endocrine disruption in both fish and human cells. Entitled “The Herbicide Atrazine Activates Endocrine Gene Networks via Non-Steroidal NR5A Nuclear Receptors in Fish and Mammalian Cells,” the University of Califonia, San Francisco (UCSF) research examines the reaction of zebrafish to environmentally relevant levels of atrazine, and mirrors the study in human placental cells. The zebrafish, which are particularly sensitive to endocrine disruptors, are “feminized” in greater proportion than the unexposed control group. Fish exposed to atrazine for 48 hours at levels found in agricultural runoff produced twice as many female fish as male.

“These fish are very sensitive to endocrine disrupting chemicals, so one might think of them as ’sentinels’ to potential developmental dangers in humans,” said senior author Holly Ingraham, PhD. “These atrazine-sensitive genes are central to normal reproduction and are found in steroid producing tissues. You have to wonder about the long-term effects of exposing the rapidly developing fetus to atrazine or other endocrine disruptors.”

In human cell studies, the researchers found that atrazine activates genes involved in hormone signally and steroid synthesis. “Endocrine-related cell types with a capacity for steroid generation appear to be especially sensitive,” researchers report. “The human data provide a brand new framework to look at atrazine,” adds Dr. Ingraham.

The study is contributing to the growing international chorus calling for regulatory action. Tim Morris, MP of the Green Party of Tasmania, said “This study from UCSF is the first to identify the full effects of atrazine on human cells, so we must take note of its worrying findings regarding the feminisation of juveniles and the disruption of human placental cells, and ban Atrazine from Tasmania until it can be proven safe for use around humans.”

Atrazine is also a concern in the United States, being the second-most widely used herbicide in the country. It is found widely in water systems in the midwest and other areas, and has a long history of contributing to developmental problems in wildlife. The greatest concern, perhaps, is that atrazine affects cells at extremely low levels. The UCSF study finds “definite effects at 2 parts per billion (ppb); the U.S. EPA has set drinking water limits for humans at 3 ppb for atrazine.”

Atrazine is not the only commonly used pesticide that causes harm at low levels. For more background on how low-dose exposure is effecting humans, see “Facing Scientific Realities: Debunking the ‘Dose Makes the Poison’ Myth.“

Sources: Environmental Science & Technology, Science Daily, The Greens Tasmania