By Kari Lydersen
Tuesday, August 25, 2009
CHICAGO, Aug. 24 -- Drinking water containing a common herbicide could pose a greater public health risk than previously thought because regular municipal monitoring doesn't detect frequent spikes in the chemical's levels, according to a report released Monday by the Natural Resources Defense Council.
The report documented spikes in atrazine in the water supplies of Midwestern and Southern towns in agricultural areas, where the herbicide is applied to the vast majority of corn, sorghum and sugar cane fields.
Atrazine, an endocrine disrupter, can interfere with the body's hormonal activity and the development of reproductive organs. The Environmental Protection Agency looks at annual average levels of the chemical in drinking-water systems, but the Natural Resources Defense Council (NRDC) says this misses spikes likely to occur after rain and springtime application of the herbicide.
"Our biggest concern is early-life-stage development," said NRDC senior scientist Jennifer Sass. "If there's a disruption during that time, it becomes hard-wired into the system. These endocrine disrupters act in the body at extremely low levels. These spikes matter."
She said the chemical could also be linked to menstrual problems and endocrine-related cancers in adults.
Scientists with atrazine manufacturer Syngenta called the NRDC study alarmist and said the spikes fall within one- and 10-day limits that the EPA considers safe.
"Atrazine is one of the best studied, most thoroughly regulated molecules on the planet," said Syngenta toxicologist Tim Pastoor. "Those momentary spikes are not going to be injurious to human health."
Under the Safe Drinking Water Act, municipal water supplies are typically tested for chemicals, including atrazine, four times a year. The EPA considers an annual average atrazine level below 3 parts per billion as safe for human consumption. But biweekly data collected by the EPA from 139 municipal water systems found that atrazine was present 90 percent of the time and that 54 water systems had one-time spikes above 3 parts per billion in 2003 and 2004, according to an analysis by the NRDC.
NRDC scientists and lawyers argue that the EPA's limits are too lenient, given studies showing the effects of low levels of atrazine on rats and other animals and the fact that it is nearly impossible to epidemiologically trace the chemical's effects on humans.
Steve Owens, assistant administrator for the EPA's office of prevention, pesticides and toxic substances, said the agency will review its atrazine policies as part of a larger reassessment of how chemicals and pesticides are regulated.
"The Obama EPA will take a hard look at atrazine and other substances," he said. "This thorough review will rely on transparency and sound science, including independent scientific peer review. We will continue to closely track new scientific developments and will determine whether a change in our regulatory position is appropriate."
Atrazine can be removed by carbon filters at water treatment plants or in households. Many water treatment plants use such filters, but others do not. The Washington Aqueduct, which treats water from the Potomac River for about 1 million Washington area customers, does not treat for atrazine because it is rarely found at levels over 0.5 parts per billion in the water.
The NRDC is asking the EPA to step up its atrazine monitoring and make the results public. The group is also encouraging farmers to greatly reduce or end use of the herbicide. Atrazine is effectively banned in the European Union, though Pastoor said a similar chemical, terbuthylazine, is widely used in Europe. He noted that atrazine, introduced in 1958, is especially attractive to farmers because it lasts for about 40 days in the soil and can be applied before, during or after planting. It is considered conducive to no-till practices that reduce a field's carbon footprint.
Atrazine is also used on lawns and golf courses in the South, and Sass said children playing on treated grass could be dangerously exposed to it. It can also concentrate in rain and fog.
Since 2003, the EPA has monitored atrazine levels in surface and ground water in 40 watersheds in the central and southern United States. The NRDC says the results raise grave concerns for wildlife and ecosystems in these areas and in the Gulf of Mexico, where much of the agricultural runoff from the Midwest ends up. Atrazine has been found to cause limb deformities and hermaphroditism in frogs at concentrations as low as 0.1 parts per billion. It is also known to kill algae and micro-organisms that make up the base of aquatic food chains, and in conjunction with other pesticides and herbicides, it suppresses animals' immune systems.
In 2003 the NRDC filed a lawsuit charging that the EPA violated the Endangered Species Act during the atrazine re-registration process by failing to adequately consult with the Fish and Wildlife Service and the National Marine Fisheries Service about how the herbicide could affect about 20 endangered species of frogs, fish, turtles and other reptiles and amphibians.
A 2008 letter from the Fish and Wildlife Service says atrazine could harm endangered Alabama sturgeon and Chesapeake Bay dwarf wedgemussel, since it is known to damage such organisms and affect food supplies, even at lower levels than what the EPA considers safe.
Negotiations between the Fish and Wildlife Service and the EPA could result in different limits or requirements for atrazine.