The EPA decision to renew the crop registration ends a long-simmering dispute between U.S. environmental groups, who want more research into potential effects of biotech crops, and the food industry, which contends gene-altered plants are useful and effective for farmers.

There are five varieties of Bt corn, made by Monsanto Co. , DuPont Co. , Dow Chemical and Syngenta AG . Most were approved by the EPA in 1995 with a federal registration that expired on Sept. 30.

The EPA said scientific studies and a history of successful use have shown Bt corn is not toxic to humans, Monarch butterflies, or other animals.

"Bt corn has been evaluated thoroughly by EPA, and we are confident that it does not pose risks to human health or to the environment," Stephen Johnson, assistant administrator of EPA's pesticide office, said in statement.

"The safeguards incorporated into these registrations will ensure that farmers can continue to use an effective, low-risk pest control alternative, which helps to protect the environment by reducing the amount of conventional pesticides used," Johnson added.

The new safeguards include requiring seed companies to monitor Bt crops to detect any insect resistance and teaching farmers how to use buffer zones around the crops.

EPA CRITICIZED BY GREEN GROUPS

Green groups said they were disappointed with the EPA decision.

"We disagree with their conclusion that the benefits outweigh any risks," said Jane Rissler, a biotech expert with the Union of Concerned Scientists.

"The seven-year renewal will make it very difficult for the agency to respond to new scientific information during the next few years," Rissler said.

Environmental groups took issue with the view of the food industry that Bt corn reduces the use of traditional chemical pesticides on corn fields.

Green groups also criticized the EPA for failing to investigate new concerns by researchers with Cornell University, Iowa State University and the University of Minnesota.

Biologists with all three schools urged the EPA last month to delay a decision, or grant a one-year provisional renewal, until more research was available on the risk for caterpillars that eat Bt pollen along with plant tissue known as corn anther.

The EPA said that it paid particular concern to the potential risk of Bt corn pollen to Monarch butterflies when evaluating whether to renew the registrations.

After reviewing "extensive data" submitted by company scientists and other experts, the EPA said the evidence "demonstrates that Bt corn does not impact Monarch butterfly populations."

The National Corn Growers Association praised the EPA.

"The EPA has conducted a two-year, in-depth study of Bt corn and determined that is poses no risks to people or the environment," the trade group said.

Global agribusiness firm Syngenta also welcomed the government's decision.

"Bt corn is the latest in a series of technologies that are helping farmers produce healthier and more abundant crops," Syngenta Seeds President Edward Shonsey said in a statement. "Proactive measures to manage the resistance of insects to Bt crops are in the long-term interest of Syngenta and individual farmers."

EPA REQUIRES NEW SAFEGUARDS

The agency said it would require Monsanto, DuPont, Syngenta and Dow to do more to ensure safe use of Bt corn, including the following:

* Teach farmers the best way to plant Bt corn to minimize the risk of insect resistance. An independent group will survey licensed growers each year to make sure they comply with the new requirements.

* Collect data about how long the Bt protein remains in the soil.

* Studies on the long-term effects on the Monarch butterfly population.

* Studies of whether birds and other insects are affected.