There is good news for corn growers still interested in using atrazine, one of the oldest and most reliable corn herbicides.
The International Agency for Research on Cancer (IARC), an arm of the United Nations World Health Organization, has removed atrazine from its list of known or suspected carcinogens.
To refresh your memory, the U.S. Environmental Protection Agency (EPA) began a special review of atrazine in 1994, to determine whether it could be used in the future.
Atrazine continues to be found in very small quantities in ground- and surface water and it was feared that the chemical might cause cancer.
However, concentrations have generally been in the 0.1 part per billion range or less in most areas. And recent groundwater analyses reveal that efforts to limit atrazine use in more fragile areas have improved water quality.
During the course of EPA's special review, hundreds of new studies have been done. EPA hasn't concluded its review of this new work. But IARC has looked over available literature and concluded that the herbicide is safe to humans.
IARC has maintained a list of known carcinogens, suspected carcinogens and non-carcinogens since 1969. In an October 1998 meeting, IARC pronounced that atrazine didn't belong on the list of known or suspected carcinogens.
"Overwhelmingly, the body of research on atrazine supports its safety to users and to the environment," says Janis McFarland, director of ag stewardship for Novartis Crop Protection, the primary producer of atrazine in the U.S.
"This new classification by the IARC supports our position that atrazine is safe to farmers, consumers and the environment when used properly. And it further demonstrates that, when new scientific research is reviewed by third-party experts, the technological advances made in the past few years can lead to changes in how we understand compounds," McFarland points out.
"However, we should not interpret the IARC findings to say we can now use atrazine without considering best management practices that will protect our water supplies," explains David Flakne. He is state government relations manager for Novartis in eight Midwestern states.
"Atrazine stewardship programs have been successful," says Flakne. "We've reduced application rates and learned how to use it in combination with other herbicides to manage weed populations. These efforts should be continued."
Maximum label rates, which had been at 4 lbs active ingredient per acre, are now set at 2.5 lbs/acre, with some exceptions where recommended rates are even lower.
"There is no reason at this time to change anything we're doing," says Mike Owen, Iowa State University extension weed control specialist. "We've learned that these lower rates work, especially in combination with other herbicides."
Flakne says that farmers should continue using atrazine where it's needed to control certain broadleaf weeds and in tankmixes or separate applications to help manage herbicide resistance.
"Using atrazine along with new, low-use-rate herbicides will help keep these chemicals effective against target weeds longer."
Atrazine also is an active ingredient in several other herbicides.
"There is no direct link between the classifications used by IARC and those used by EPA," Flakne admits. "However, EPA will be looking at many of the same studies evaluated by IARC, so we feel this is positive news for atrazine."
Flakne believes that EPA will re-register atrazine following its special review, which is expected to conclude by the fall of 2000.