(Beyond Pesticides, November 21, 2003)
According to Science News, a new study has found chlorpyrifos, a neurotoxic organophosphate insecticide commonly sold as Dursban, was recently found to damage heart and liver cells, in addition to the affects it is already known to have on the brain. Although chlorpyrifos had many of its uses “phased-out” by an agreement between EPA and the pesticide industry in 2000, it may still be used on golf courses, in baits, in agriculture, for mosquito control and in food processing plants. Existing stocks purchased before 2002 may be used indefinitely.
To test for effects of the chemical outside the nervous system, researchers at Duke University in Durham, N.C., injected rats daily with 1, 2, or 5 milligrams of chlorpyrifos per kilogram of body weight for 4 consecutive days. Some animals received the injections while they were pregnant, and their offspring were then studied for possible effects. Other animals were exposed during the first or second week of life. The researchers looked for effects shortly after exposure and when the animals were juveniles and adults.
While the doses of chlorpyrifos were too low to cause immediate symptoms, rats exposed in utero or during the first week after birth later showed subtle biochemical abnormalities. Chlorpyrifos exposure in older animals seldom had an effect, suggesting that a “window of vulnerability” closes soon after birth, say Theodore Slotkin, PhD, and his colleagues at Duke.
The abnormalities affect adenylyl cyclase signaling, a process by which cells communicate, and in some experiments, effects were evident only in male rats. Because adenylyl cyclase signaling modifies insulin production, glucose metabolism, and heart rate, the findings imply that early exposure to chlorpyrifos and other organophosphates could increase risks for cardiovascular and metabolic disorders that typically arise later in life, Dr. Slotkin argues.