Chances are, you've never heard of flubendiamide. It's not among the most toxic insecticides, and it's not among the widely used chemicals, either. In recent years, it has been used on about a quarter of the nation's tobacco and 14 percent of almonds, peppers and watermelons.

But flubendiamide is now at the center of a public dispute between the Environmental Protection Agency and the company that sells it, Bayer CropScience. That dispute is arousing fear in the pesticide industry — and hope among activists who are pushing for the EPA to regulate pesticides more tightly.

The EPA wants to cancel its approval of this pesticide. The agency says that there is now evidence that this chemical will accumulate in streams and lakes, where it will kill off small, freshwater creatures like snails and crabs that play a crucial role in the entire web of aquatic life.

But the real reason that this decision is attracting so much attention is that flubendiamide is just one of thousands of pesticides that the EPA approved on a "conditional" basis, pending the results of further studies that were required to assure that agency of the chemicals' safety. The pesticide industry fears — and anti-pesticide groups hope — that many other chemicals, also approved conditionally, soon could face increased EPA scrutiny as well.

"We're really encouraged that the EPA went for cancellation" of flubendiamide's approval, rather than a lengthy process known as a "special review," says Kristin Schafer, policy director at the Pesticide Action Network, or PAN.

Conditional approvals allow the EPA to OK a pesticide when the benefits of using it outweigh any apparent risks — such as in a public health emergency. But pesticide critics such as PAN and the Natural Resources Defense Council have criticized the EPA's heavy reliance on this process. They say it has turned into an easy way for companies to start selling their products without really proving that their products meet legal safety requirements — and that the EPA seldom follows up.

In the case of flubendiamide, the EPA was concerned, from the beginning, about the possibility that the chemical would accumulate in water. The agency has now concluded that this is likely.

The company that sells the pesticide, Bayer CropScience, is refusing, so far, to stop selling the chemical. The company says that the EPA is relying on computer models that overstate the environmental risks, rather than observations of flubendiamide in the real world.

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